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How are dtLinks created in NavMesh

金庆 — Fri, 18 Nov 2022 02:03:00 GMT

How are dtLinks created in NavMesh

(Jin Qing's Column, Nov., 2022)

`dtLink`

dtLink defines a link between 2 polygons. It is an internal data structure.

A dtLink is owned by its source polygon.

How link is used

The links are used in findPath(), to search all the neighbor polygons, from the current best polygon.

fields of `dtLink`

dtLink has 2 required fields:

neighbor: the neighbor polygon reference that is linked to.
edge: index of the polygon edge that owns this link. It is used in getPortalPoints() and raycast().

If the link is a boundary link, which links to other tile, then it has more fields:

side: defines on which side the link is. 8 sides. It is used in findPath() and raycast().
bmin: defines the minimum sub-edge area.
bmax: defines the maximum sub-edge area. bmin and bmax are used in portal finding.

How are links created

Links are not saved to navmesh file. They are created on navmesh loading in addTile().

dtNavMesh::addTile() add a tile to the navmesh. A tile is a square block of the map.

The main job of dtNavMesh::addTile() is to create links inside this tile and between this tile and other tiles. Actually a block indexed by (x, y) of constant size has many layers for multi-floor map. A dtMeshTile is actually a layer with an index of (x, y, layer).

5 steps to create all links:

1. Connect internal links

connectIntLinks() iterates all the polygons in the tile and create links for them by the help of neighbors information of the polygons.

2. Base off-mesh connections

baseOffMeshLinks() bases off-mesh connections to their starting polygons and connect connections inside the tile.

Off-mesh connection is between 2 points which are inside a tile or between 2 adjacent tiles.

For each off-mesh connection, there creates a specific polygon consisting of 2 vertices. See DT_POLYTYPE_OFFMESH_CONNECTION.

baseOffMeshLinks() creates 2 links for each off-mesh connection:

From the off-mesh connection polygon to the source polygon
From the source polygon to the off-mesh connection polygon

The destinaton polygon of the off-mesh connection is skipped here.

3. Connect external off-mesn links within this tile

connectExtOffMeshLinks() with the source and target tile be this tile.

connectExtOffMeshLinks() searches off-mesh connections that are from this tile to the target tile by checking the side direction of the connection.

It creates a link from off-mesh connection polygon to the target tile. For bidirectional connection, it also creates a link from the target polygon to the off-mesh connection polygon.

So for each off-mesh connection of this tile, 3 or 4 links are created by baseOffMeshLinks() and connectExtOffMeshLinks(), one on the source polygon, one on the destination polygon and 1/2 on the off-mesh connection polygon.

4. Connect with layers in current tile

For each layer other than this layer in this tile:

Create links from this layer to other layer
Create links from other layer to this layer
Create links of the off-mesh connection from this layer to other layer
Create links of the off-mesh connection from other layer to this layer

5. Connect with neighbour tiles

Check 9 neighbor tiles' layers, and create links just like previous step:

Create links from this layer to neighnor layer
Create links from neighnor layer to this layer
Create links of the off-mesh connection from this layer to neighnor layer
Create links of the off-mesh connection from neighnor layer to this layer

By now, for every off-mesh connection of all the loaded tiles, 3/4 links are created.

Reference

https://blog.csdn.net/icebergliu1234/article/details/80322392

金庆 2022-11-18 10:03 发表评论

C++ parameter passing rules

金庆 — Sat, 29 Oct 2022 03:01:00 GMT

C++ parameter passing rules

From: https://www.modernescpp.com/index.php/c-core-guidelines-how-to-pass-function-parameters

Parameter passing expression rules:

F.15: Prefer simple and conventional ways of passing information
F.16: For “in” parameters, pass cheaply-copied types by value and others by reference to const
F.17: For “in-out” parameters, pass by reference to non-const
F.18: For “consume” parameters, pass by X&& and std::move the parameter
F.19: For “forward” parameters, pass by TP&& and only std::forward the parameter
F.20: For “out” output values, prefer return values to output parameters
F.21: To return multiple “out” values, prefer returning a tuple or struct
F.60: Prefer T* over T& when “no argument” is a valid option

金庆 2022-10-29 11:01 发表评论

Implementation of user data in cursive::Cursive

金庆 — Sun, 02 Oct 2022 08:38:00 GMT

Implementation of user data in cursive::Cursive

(Jin Qing's Column, Oct., 2022)

cursive::Cursive can store any user data:

pub struct Cursive {
    ...
    // User-provided data.
    user_data: Box<dyn Any>,
}
impl Cursive {
    ...
    pub fn set_user_data(&mut self, user_data: T) {
        self.user_data = Box::new(user_data);
    }
    pub fn user_data(&mut self) -> Option<&mut T> {
        self.user_data.downcast_mut()
    }
    pub fn take_user_data(&mut self) -> Option {
        ...
    }
    pub fn with_user_data(&mut self, f: F) -> Option
    where
        F: FnOnce(&mut T) -> R,
        T: Any,
    {
        self.user_data().map(f)
    }

Example:

let mut siv = cursive_core::Cursive::new();
// Start with a simple `Vec` as user data.
siv.set_user_data(vec![1i32, 2, 3]);
assert_eq!(siv.user_data::<Vec<i32>>(), Some(&mut vec![1i32, 2, 3]));
// Let's mutate the data a bit.
siv.with_user_data(|numbers: &mut Vec<i32>| numbers.push(4));
// If mutable reference is not enough, we can take the data by value.
let data: Vec<i32> = siv.take_user_data().unwrap();
assert_eq!(data, vec![1i32, 2, 3, 4]);
// At this point the user data was removed and is no longer available.
assert_eq!(siv.user_data::<Vec<i32>>(), None);

金庆 2022-10-02 16:38 发表评论

Naming Conventions for Accessors

金庆 — Thu, 22 Sep 2022 08:02:00 GMT

Naming Conventions for Accessors

from: C++ Programming Guidelines (cginternals.github.io)

When naming accessors within classes, non-trivial getters and queries, i.e., those that perform calculations, you should prepended get. All other getters have no prefix and setters have the set prefix.

class Object
{
public:
  int radius() const;
  void setRadius(int value);

  int getPerimeter();

private:
  int m_radius;
};

int Object::radius() const
{
    return m_radius;
}

void Object::setRadius(int value)
{
    m_radius = value;
}

int Object::getPerimeter()
{
    return 2 * pi * m_radius;
}

金庆 2022-09-22 16:02 发表评论

Rust sometimes needs manual type annotation

金庆 — Fri, 29 Apr 2022 02:14:00 GMT

Rust sometimes needs manual type annotation

(Jin Qing's Column, Apr., 2022)

This code compiles error:

      trait MyCallback: FnMut(&u32) -> () { }
impl ()> MyCallback for F { }
fn process_data(mut f: impl MyCallback) -> () {
    f(&0)
}
fn process_data_2(mut f: impl FnMut(&u32) -> ()) -> () {
    f(&0)
}
fn main() {
    // Doesn't compile
    process_data(|_| ());
    // Compiles
    process_data_2(|_| ());
}

      expected type `for<'r> FnMut<(&'r u32,)>`
              found type `FnMut<(&u32,)>`

Fix:

          process_data(|_: &_| ());

See: https://stackoverflow.com/questions/61671460/rust-type-mismatch-resolving-forr-with-closure-trait-alias-argument

Also see: https://github.com/rust-lang/rust/issues/58639

Sometimes, Rust needs a type annotation in closure.

金庆 2022-04-29 10:14 发表评论

Fix recastnavigation contour error

金庆 — Thu, 28 Apr 2022 05:34:00 GMT

ix recastnavigation contour error

(Jin Qing's Column, Apr., 2022)

Using navmesh generated by recastnavigation, we found the agent will collide into the wall when it is walking along the navmesh path.

After some inspection, we found the reason is that at the collision position, the position on the path is simply too close to the wall, which is less than the agent radius.

If the agent radius is zero, the navmesh contour may inside the wall.

Displaying the raw contour and contour, we can see the raw contour which is jigsaw shaped is right, but the simplied contour uses a straight line to replace the jigsaw edge, and causes the error.

The parameter "Max Edge Error" controls how the contour is simplified, which default is 1.3, which means a vertex can deviate from the final contour in the range of 1.3 times of cell size.

We hope the error is on only one side of the contour instead of on both sides. In other words, the contour should within the raw contour.

walkContour() finds a raw contour which is a polygon. simplifyContour() simplifies the raw contour resulting a simpler polygon.

The steps of simplifyContour():

Find lower-left and upper-right vertices of the contour to form the initial simplified polygon.
For each edge of the simplified polygon
1. For each point between 2 points of the edge
  1. Find the point that is the most distant from the edge
2. If the distance is larger than the max error, add the point to the simplified polygon
Split too long edges.

We make these modifications:

The distance is signed
- If the point is outside the walkable area, just make sure it is less than the max error
- If the point is inside the walkable area
  - Add it to the simplified polygon to make sure the final contour is within the raw area

There are 2 kinds of contour:

Outline of a walkable area
Hole of a walkable area

We should decide the kind of the contour before simplifyContour(). If the start cell (x, y) is in the raw contour polygon, then it is an outline not a hole contour. Because (x, y) may be one of the vetex of the polygon, we use (x + 0.5, y + 0.5) instead, which is the center of the cell.

The result will be like this:

Compare with the orignal contour:

金庆 2022-04-28 13:34 发表评论

How to work around rustup-init failure

金庆 — Sun, 24 Apr 2022 06:09:00 GMT

How to work around rustup-init failure

(Jin Qing's Column, Mar., 2022)

rustup-init.exe may fail if some anti-virus software is running with realtime protection.

The error message is like this after many retries:

error: could not rename component file from 'C:\.../rust/html' to 'C:\.../rust/html'

See: https://github.com/rust-lang/rustup/issues/1912

And it is not possible to stop the anti-virus for a corporate laptop.

There is a way to workaround this. Here are the steps:

Run rustup-init until it begins to retry renaming
Kill rustup-init when it is retrying
- rustup will be installed before the failure
- do not let rustup-init do the cleanup after the final failure
Run rustup update to install all.
Run rustup-init again to setup others.

rustup update will report that rustc was not found:

C:\Users\jinqing01>rustup update
info: syncing channel updates for 'stable-x86_64-pc-windows-msvc'
...
info: removing previous version of component 'rustc'
warning: during uninstall component rustc was not found
...
info: installing component 'rustc'
...  
info: checking for self-updates
  stable-x86_64-pc-windows-msvc updated - rustc 1.59.0 (9d1b2106e 2022-02-23) (from (rustc does not exist))
info: cleaning up downloads & tmp directories

Rerun rustup-init to setup the toolchain:

C:\Users\jinqing01>cargo --version
error: no override and no default toolchain set
C:\Users\jinqing01>d:
D:\>cd tool
D:\Tool>rustup-init.exe
Welcome to Rust!
This will download and install the official compiler for the Rust
programming language, and its package manager, Cargo.
...
Rust is installed now. Great!
Press the Enter key to continue.
D:\Tool>cargo --version
cargo 1.59.0 (49d8809dc 2022-02-10)

金庆 2022-04-24 14:09 发表评论

Closure as the function parameter

金庆 — Sun, 24 Apr 2022 06:06:00 GMT

Closure as the function parameter

(Jin Qing's Column, Mar., 2022)

It is best to let the function take a closure trait as the parameter instead of a function pointer.

      fn foo(f: fn()) {
    f()
}
fn main() {
    foo(|| println!("hello"));
    let a = 123;
    foo(move || println!("{}", a))
}

compiles error:

      error[E0308]: mismatched types
 --> src/main.rs:9:9
  |
9 |     foo(move || println!("{}", a))
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^ expected fn pointer, found closure
  |
  = note: expected fn pointer `fn()`
                found closure `[closure@src/main.rs:9:9: 9:34]`
note: closures can only be coerced to `fn` types if they do not capture any variables
 --> src/main.rs:9:32
  |
9 |     foo(move || println!("{}", a))
  |                                ^ `a` captured here
For more information about this error, try `rustc --explain E0308`.

https://doc.rust-lang.org/book/ch19-05-advanced-functions-and-closures.html

Function pointers implement all three of the closure traits (Fn, FnMut, and FnOnce), so you can always pass a function pointer as an argument for a function that expects a closure. It’s best to write functions using a generic type and one of the closure traits so your functions can accept either functions or closures.

金庆 2022-04-24 14:06 发表评论

Deadlock detection must not run as tokio task

金庆 — Sun, 24 Apr 2022 06:04:00 GMT

deadlock detection must not run as tokio task

(Jin Qing's Column, Feb., 2022)

parking_lot has an experimental feature: deadlock_detection.

See: https://amanieu.github.io/parking_lot/parking_lot/deadlock/index.html

use std::thread;
use std::time::Duration;
use parking_lot::deadlock;
// Create a background thread which checks for deadlocks every 10s
thread::spawn(move || {
loop {
thread::sleep(Duration::from_secs(10));
let deadlocks = deadlock::check_deadlock();
if deadlocks.is_empty() {
continue;
}
println!("{} deadlocks detected", deadlocks.len());
for (i, threads) in deadlocks.iter().enumerate() {
println!("Deadlock #{}", i);
for t in threads {
println!("Thread Id {:#?}", t.thread_id());
println!("{:#?}", t.backtrace());
}
}
}
});

The output is like this:

1 deadlocks detected
Deadlock #0
Thread Id 16072
0: 0x7ff985cb659d - backtrace::backtrace::dbghelp::trace
at d:\Users\jinqing\.cargo\registry\src\github.com-1ecc6299db9ec823\backtrace-0.3.63\src\backtrace\dbghelp.rs:98
...
13: 0x7ff985ae92f3 - lock_api::rwlock::RwLock::read
at d:\Users\jinqing\.cargo\registry\src\github.com-1ecc6299db9ec823\lock_api-0.4.6\src\rwlock.rs:448
14: 0x7ff985aeadf3 - cgc::scene::SceneData::check_body_collide
at E:\gitlab\yserver\gc\src\scene.rs:99
...
81: 0x7ff9f29b7034 - BaseThreadInitThunk
82: 0x7ff9f2b02651 - RtlUserThreadStart

But the deadlock detection thread can not be changed to a tokio task, because if deadlock happens, all tasks may be blocked, including the deadlock detection, causing no deadlock error output.

In the following example, if the number of the deadlock tasks is larger than the thread number of tokio runtime, all tasks will be blocked.

use std::{thread, time::Duration};
use parking_lot::RwLock;
use tokio::time;
#[tokio::main]
async fn main() {
tokio::spawn(async move {
for i in 0..999999 {
println!("{}", i);
time::sleep(Duration::from_secs(1)).await;
}
});
const MAX: i32 = 100;
for _ in 0..MAX {
tokio::spawn(async move {
{
// DEADLOCK!
let a = RwLock::new(());
let _g1 = a.write();
let _g2 = a.write();
}
time::sleep(Duration::from_secs(9999)).await;
});
}
println!("Hello, world!");
thread::sleep(Duration::from_secs(10));
}

The output is:

0
Hello, world!
_

If no deadlock, or the number of deadlock tasks is small, the output should be:

0
Hello, world!
1
2
3
...

金庆 2022-04-24 14:04 发表评论

TortoiseGit is OK but GitExtensions fails

金庆 — Sun, 24 Apr 2022 06:01:00 GMT

TortoiseGit is OK but GitExtensions fails

GitExtensions and Git fail:

      "git" pull --progress "origin"
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
Done
Press Enter or Esc to exit...

But TortoiseGit is OK.

      git.exe pull --progress -v --no-rebase "origin"
From github.com:jinq0123/recastnavigation
= [up to date]      master      -> origin/master
= [up to date]      release-2.0 -> origin/release-2.0
Already up to date.

ssh -T shows that the reason is there is no id files:

      PS d:\github> ssh -vT git@github.com
OpenSSH_for_Windows
debug1: Connecting to github.com [20.205.243.166] port 22.
debug1: Connection established.
debug1: identity file C:\\Users\\jinqing/.ssh/id_rsa type -1
debug1: identity file C:\\Users\\jinqing/.ssh/id_xmss-cert type -1
debug1: Authenticating to github.com:22 as 'git'
debug1: Host 'github.com' is known and matches the ED25519 host key.
debug1: Found key in C:\\Users\\jinqing/.ssh/known_hosts:2
debug1: Will attempt key: C:\\Users\\jinqing/.ssh/id_rsa
debug1: Will attempt key: C:\\Users\\jinqing/.ssh/id_xmss
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: C:\\Users\\jinqing/.ssh/id_rsa
debug1: Trying private key: C:\\Users\\jinqing/.ssh/id_xmss
debug1: No more authentication methods to try.
git@github.com: Permission denied (publickey).
PS d:\github>

Copy my RSA key file rsa.ppk that TortoiseGit uses as ~/.ssh/id_rsa:

      PS D:\jinqing\github_jinq\recastnavigation> ssh -T git@github.com
Load key "C:\\Users\\jinqing/.ssh/id_rsa": invalid format
git@github.com: Permission denied (publickey).
PS D:\jinqing\github_jinq\recastnavigation>

Open TortoiseGit/bin/puttygen.exe, load rsa.ppk, then Convensionis->Export OpenSSH key as ~/.ssh/id_rsa:

      PS D:\jinqing\github_jinq\recastnavigation> ssh -T git@github.com
Hi jinq0123! You've successfully authenticated, ...

id_rsa begins with:

      -----BEGIN RSA PRIVATE KEY-----

金庆 2022-04-24 14:01 发表评论

Tracing usage

金庆 — Sun, 02 Jan 2022 04:38:00 GMT

Tracing usage

(Jin Qing's Column, Jan., 2022)

Tracing is Rust log crate: https://github.com/tokio-rs/tracing

This example code outputs log to stdout and a log file, using a log filter config file, which can be automatically reloaded on change.

https://gitee.com/jinq0123/tracing-example

Dependencies

Add these dependencies to Cargo.toml:

      [dependencies]
anyhow = "1.0.52"
hotwatch = "0.4.6"
tracing = "0.1.29"
tracing-appender = "0.2.0"
tracing-subscriber = { version = "0.3.5", features = [ "env-filter", "json" ] }

main.rs

      mod log;
use anyhow::Result;
use std::{thread, time::Duration};
use tracing::info;
fn main() -> Result<()> {
    let _guard = log::init("./log", "example.log", "config/log_filter.txt")?;
    for i in 0..999 {
        info!(i, "Hello, world!");
        thread::sleep(Duration::from_secs(1));
    }
    Ok(())
}

log.rs

      //! Init log.
//!
use anyhow::{anyhow, Context as _, Result};
use hotwatch::{Event, Hotwatch};
use std::fs;
use std::path::Path;
use tracing::{debug, warn, Subscriber};
use tracing_appender::{non_blocking::WorkerGuard, rolling};
use tracing_subscriber::{fmt, layer::SubscriberExt, reload::Handle, EnvFilter};
/// Inits log.
/// Returns a WorkerGuard to ensure buffered logs are flushed,
///  and a Hotwatch to watch the log filter file.
pub fn init(
    directory: impl AsRef,
    file_name_prefix: impl AsRef,
    log_filter_file: impl AsRef,
) -> Result<(WorkerGuard, Hotwatch)> {
    let file_appender = rolling::daily(directory, file_name_prefix);
    let (non_blocking, worker_guard) = tracing_appender::non_blocking(file_appender);
    let file_layer = fmt::Layer::default()
        .with_writer(non_blocking)
        .json()
        .flatten_event(true)
        .with_ansi(false);
    let builder = tracing_subscriber::fmt()
        .pretty()
        .with_env_filter(EnvFilter::from_default_env())
        .with_filter_reloading();
    let handle = builder.reload_handle();
    let subscriber = builder.finish();
    let subscriber = subscriber.with(file_layer);
    tracing::subscriber::set_global_default(subscriber).context("set global default subscriber")?;
    reload_filter(handle.clone(), log_filter_file.as_ref());
    let log_filter_path_buf = log_filter_file.as_ref().to_path_buf();
    let mut hotwatch = Hotwatch::new().context("hotwatch failed to initialize!")?;
    hotwatch
        .watch(log_filter_file.as_ref(), move |event: Event| {
            debug!("log filter file event: {:?}", event);
            if let Event::Write(_) = event {
                reload_filter(handle.clone(), log_filter_path_buf.clone());
            }
        })
        .with_context(|| format!("failed to watch file: {:?}", log_filter_file.as_ref()))?;
    Ok((worker_guard, hotwatch))
}
fn reload_filter(
    handle: Handle,
    log_filter_file: impl AsRef,
) {
    let res = try_reload_filter(handle, log_filter_file);
    match res {
        Ok(_) => debug!("reload log filter OK"),
        Err(e) => warn!("reload log filter error: {:?}", e),
    }
}
fn try_reload_filter(
    handle: Handle,
    log_filter_file: impl AsRef,
) -> Result<()> {
    let contents = fs::read_to_string(log_filter_file.as_ref()).with_context(|| {
        format!(
            "something went wrong reading the file: {:?}",
            log_filter_file.as_ref()
        )
    })?;
    let contents = contents.trim();
    debug!("reload log filter: {:?}", contents);
    let new_filter = contents
        .parse::()
        .map_err(|e| anyhow!(e))
        .context("failed to parse env filter")?;
    handle.reload(new_filter).context("handle reload error")
}

log_filter.txt

log_filter.txt is the configure file for log. The change of this file will trigger the reload.

The log filter file must exist, otherwise it will be error:

      Error: failed to watch file: "config/log_filter.txt"
Caused by:
    �pȝ��找不到指定的路径�?(os error 3)

The content of log_filter.txt is a single line of filter string. A filter string consists of one or more comma-separated directives. The directive syntax is similar to RUST_LOG env val of env_logger’s.

      target[span{field=value}]=level

See: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/struct.EnvFilter.html

Example

tracing_example enables logs that:
- target is modules of tracing_example*
info will enable logs that:
- level is info
tracing_ex=info enables logs that:
- target is modules of tracing_ex*
- level is info or above
info,tracing_ex=debug enables logs that:
- level is info or above
- or target is tracing_ex* and level is debug
[foo]=trace enables logs that:
- within the span foo
- level is trace or above
[span_b{name=\"bob\"}] enables logs that:
- have any target,
- are inside a span named span_b,
- which has a field named name with value bob,
- at any level.

Note: span filter directive will keep effective until it exits the span.

金庆 2022-01-02 12:38 发表评论

Try tracing

金庆 — Sat, 01 Jan 2022 12:35:00 GMT

Try tracing

(Jin Qing's Column, Dec., 2021)

https://github.com/tokio-rs/tracing

Usage on github

Switch to tag tracing-0.1.29 first. The master's examples can not build. Subscriber is renaming to collector on master.

tracingsubscriber in 0.1.29 has been renamed to tracingcollect on master.

In Applications
In Libraries
In async

The example is using tracing_subscriber::fmt, which can be configured by RUST_LOG env val.

By default, no log is output. Set RUST_LOG=info before running, and the log is:

      Dec 25 10:23:11.200  INFO tracing_test: preparing to shave yaks number_of_yaks=3
Dec 25 10:23:11.203  INFO tracing_test: yak shaving completed. all_yaks_shaved=true

span
set_global_default()
tracingcollectwith_default()

Usage of RUST_LOG.

RUST_LOG is defined in env_logger

Default disabled except error
RUST_LOG is comma-separated directives
- Directive form: examplelogtarget=level
  - The log target is a prefix
    - If target is ommitted, then all modules are set
  - The level is "all" if ommitted
    - off, error, warn, info, debug, trace
- Regex filter: error,hello=warn/[0-9]scopes
  - For all directives

Usage on crates.io

It is slightly different from the github.

Uses set_global_default()
Explains some concepts
- span
- event

Span filter? [my_span]=info

Document

https://docs.rs/tracing/0.1.29/tracing/

The document is much more detailed than github and crates.io.

Code examples

Run example:

      cargo run --example counters

Write to file

fmt-multiple-writers:

Change to write to current dir
- tracing_appender::rolling::hourly(".", ...
Do not write ANSI color to file
- .with(fmt::Layer::new().with_writer(non_blocking).with_ansi(false));

Dynamic level

tower-load

with_filter_reloading() -> reload handl -> handle.reload(new_filter)
new filter is send through http

https://github.com/tokio-rs/tracing/issues/1629 tracing_subscriber::reload

They use the same tracing_subscriber::reload::Handle::reload()

Filters and Layers

https://docs.rs/tracing-subscriber/0.3.4/tracing_subscriber/layer/index.html#filtering-with-layers

Reload from config file

It is desired to reconfigure the log filter in the runtime by SIGHUP, or watch configure file change. It can use notify crate to watch file.

      use anyhow::{anyhow, Context as _, Result};
use hotwatch::{Event, Hotwatch};
use std::{fs, thread, time::Duration};
use tracing::{debug, info, warn, Subscriber};
use tracing_subscriber::{reload::Handle, EnvFilter};
const CFG: &str = "cfg.txt";
fn main() -> Result<()> {
    let builder = tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env())
        .with_filter_reloading();
    let handle = builder.reload_handle();
    builder
        .try_init()
        .map_err(|e| anyhow!(e))
        .context("failed to init subscriber builder")?;
    tracing::info!("Before reload");
    reload_cfg(handle.clone());
    let mut hotwatch = Hotwatch::new().context("hotwatch failed to initialize!")?;
    hotwatch
        .watch(CFG, move |event: Event| {
            if let Event::Write(_) = event {
                reload_cfg(handle.clone());
            }
        })
        .context("failed to watch file")?;
    for i in 0..999 {
        info!(i);
        thread::sleep(Duration::from_secs(1));
    }
    Ok(())
}
fn reload_cfg(handle: Handle) {
    let res = try_reload_cfg(handle);
    match res {
        Ok(_) => debug!("reload cfg OK"),
        Err(e) => warn!("reload cfg error: {:?}", e),
    }
}
fn try_reload_cfg(handle: Handle) -> Result<()> {
    let contents = fs::read_to_string(CFG).context("something went wrong reading the file")?;
    let contents = contents.trim();
    debug!("reload cfg: {:?}", contents);
    let new_filter = contents
        .parse::()
        .map_err(|e| anyhow!(e))
        .context("failed to parse env filter")?;
    handle.reload(new_filter).context("handle reload error")
}

How to new a Subscriber with tracing-subscriber

SubscriberBuilder:
- fmt().init()
- with_env_filter()
- with_filter_reloading()
- reload_handle()
- finish() to get a Subscriber and then add a file Layer?
  - https://github.com/tokio-rs/tracing/issues/971
Registry:
- registry().with...()
- Currently, the [Registry] type provided by this crate is the only [Subscriber] implementation capable of participating in per-layer filtering.
FmtSubscriber
- new it manually
- need SubscriberBuilder to configure

金庆 2022-01-01 20:35 发表评论

Box doesn't implement the trait

金庆 — Tue, 21 Dec 2021 07:09:00 GMT

From:

By default a Box doesn't implement the trait of the object it contains. This means that trying to construct PeopleZoo> won't work out of the box and will give a type error.

Because of this, it's good practice to give a default implementation of your trait for it's boxed counterpart. This can be done by calling as_ref or as_mut on the Box and calling the references relevant method.

For just a small bit of effort you can help a bunch of people that may consume your struct.

trait Person { fn say_hello(&self); } impl Person for Box<dyn Person> { fn say_hello(&self) { self.as_ref().say_hello() } }

struct PeopleZoo<P: Person> {
    people: Vec<P>,
}

fn main() { let mut zoo: PeopleZoo<Box<dyn Person>> = PeopleZoo { people: vec![] }; }

金庆 2021-12-21 15:09 发表评论

minikube DNS fails after SRV query

金庆 — Fri, 10 Dec 2021 02:46:00 GMT

minikube DNS fails after SRV query

(Jin Qing's Column, Dec., 2021)

My program is using K8s DNS SRV query to discovery service, and when it's deployed on minikube, I find DNS failure.

I can use nslookup to reproduce the failure.

Querying a FQDN is OK. But after querying a non-existing SRV short name, the ping fails.

root@web-0:/# ping google.com
PING google.com (142.250.66.110) 56(84) bytes of data.
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=1 ttl=108 time=33.7 ms
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=2 ttl=108 time=33.8 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 33.779/33.834/33.889/0.055 ms
root@web-0:/# nslookup
> set type=srv
> nosuch-nosuch-nosuch-1234567890abcdefg.cn
Server:         10.96.0.10
Address:        10.96.0.10#53
** server can't find nosuch-nosuch-nosuch-1234567890abcdefg.cn: NXDOMAIN
> exit
root@web-0:/# ping google.com
PING google.com (142.250.66.110) 56(84) bytes of data.
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=1 ttl=108 time=33.7 ms
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=2 ttl=108 time=33.7 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 33.730/33.735/33.741/0.183 ms
root@web-0:/# nslookup
> set type=srv
> nginx-wrong
Server:         10.96.0.10
Address:        10.96.0.10#53
** server can't find nginx-wrong: SERVFAIL
> exit
root@web-0:/# ping google.com
ping: unknown host google.com
root@web-0:/#

The ping will recover to normal after about 1 minute.

If I query a existing internal service name, and nslookup returns correctly, then DNS is OK after I quit nslookup.

root@web-0:/# ping google.com
PING google.com (142.250.66.110) 56(84) bytes of data.
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=1 ttl=108 time=33.6 ms
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=2 ttl=108 time=34.8 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 33.648/34.260/34.872/0.612 ms
root@web-0:/# nslookup
> set type=srv
> nginx
Server:         10.96.0.10
Address:        10.96.0.10#53
nginx.default.svc.cluster.local service = 0 25 80 web-1.nginx.default.svc.cluster.local.
nginx.default.svc.cluster.local service = 0 25 80 web-2.nginx.default.svc.cluster.local.
nginx.default.svc.cluster.local service = 0 25 80 web-0.nginx.default.svc.cluster.local.
nginx.default.svc.cluster.local service = 0 25 80 web-3.nginx.default.svc.cluster.local.
> exit
root@web-0:/# ping google.com
PING google.com (142.250.66.110) 56(84) bytes of data.
64 bytes from hkg12s28-in-f14.1e100.net (142.250.66.110): icmp_seq=1 ttl=108 time=33.5 ms
^C
--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 33.529/33.529/33.529/0.000 ms
root@web-0:/#

When DNS fails, the whole cluster can not query any domain name outside, but internal name is OK.

https://github.com/kubernetes/minikube/issues/13137

金庆 2021-12-10 10:46 发表评论

DeathVoteExpirationTimeout in Orleans

金庆 — Wed, 08 Dec 2021 01:43:00 GMT

DeathVoteExpirationTimeout in Orleans

(Jin Qing's Column, Dec., 2021)

Try to find out why Orleans need a DeathVoteExpirationTimeout config.

https://dotnet.github.io/orleans/docs/implementation/cluster_management.html#extension-to-totally-order-membership-views

DeathVoteExpirationTimeout - Expiration time in seconds for death vote in the membership table. Default is 120 seconds

GetFreshVotes

DeathVoteExpirationTimeout is only used by GetFreshVotes(), which has 3 occurence:

    class ClusterHealthMonitor
    {
        ...
        private UpdateMonitoredSilos(...)
        {
            ...
            bool isSuspected = candidateEntry.GetFreshVotes(now, DeathVoteExpirationTimeout).Count > 0;
            ...
        }
    }

    class LocalSiloHealthMonitor
    {
        ...
        private int CheckSuspectingNodes(DateTime now, List complaints)
        {
            ...
            var freshVotes = membershipEntry.GetFreshVotes(now, DeathVoteExpirationTimeout);
            ...
        }
        ...
    }

    class MembershipTableManager
    {
        ...
        public TryToSuspectOrKill(SiloAddress silo)
        {
            ...
            // get all valid (non-expired) votes
            var freshVotes = entry.GetFreshVotes(DateTime.UtcNow, DeathVoteExpirationTimeout);
            ...
        }
        ...
    }

GetFreshVotes() uses this expiration time to ignore old voter:

        internal GetFreshVotes(DateTime now, TimeSpan expiration)
        {
            ...
            foreach (var voter in this.SuspectTimes)
            {
                var otherVoterTime = voter.Item2;
                if (now.Subtract(otherVoterTime) < expiration)
                {
                    result.Add(voter);
                }
            }
            return result.ToImmutable();
        }

金庆 2021-12-08 09:43 发表评论

How to delete local branches of GitExtension

金庆 — Tue, 07 Dec 2021 09:04:00 GMT

How to delete local branches of GitExtension

(Jin Qing's Column, Dec., 2021)

GitExtension is a good tool. After a long time of usage, my branch list finally reaches over a full screen, and it is hard to select the branch I want.

GitExtension always remembers all the branches of remote and local, even they have been deleted.

I tried to find a way to delete these branches which are already merged, but resulted in futile.

It has a plugin names "Delete obsolete branches", but I don't know how to use it.

Finally I renamed the work directory, and cloned a new one, which clears all the branches. It seems that these branches are stored in local .git directory. If let GitExt open the renamed directory, these branches reappears.

Reference:

https://talk.plesk.com/threads/git-extension-doesnt-remove-deleted-branches.351838/
https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/39296707-git-extension-option-to-delete-branches

金庆 2021-12-07 17:04 发表评论

��日志 slog �Ҏ�� tracing

金庆 — Wed, 24 Nov 2021 10:18:00 GMT

��日志 slog �Ҏ�� tracing

(金庆的专�?2021.11)

slog 不是立即写盘�Q�最后的几行日志会丢�?/p>
- tracing 不会丢日�?/li>
slog 不支持运行中动态更�Ҏ��志等�U?/p>
- tracing with_filter_reloading()
  - examples/tower-load
slog 不支持不同包讄��不同日志�{��
- tracing 可单独打开某个模块的日�?/li>
发现一��?slog panic: panicked at 'slog::Fuse Drain: Fatal(Custom { kind: BrokenPipe, error: "The logger thread terminated" })'
- 搜到相同错误�Q?a target='_blank' class='url'>https://github.com/mimblewimble/grin/issues/946
  - 别�h的解��x��法是: 不用slog�?/li>
slog 主页10月添加推荐��?tracing
slog 按线�E�保存上下文�Q�tracing 按协�E�保存上下文
tracing github star 1.9K > slog 1.2K
tracing crates 下蝲 21M > sloggers 0.4M, slog-scope 2.6M, slog-stdlog 1.9M
tracing vs slog: https://www.reddit.com/r/rust/comments/kdo29n/slog_vs_tracing_which_one_do_you_prefer/
Rust compiler 2020�q�已改用 tracing�Q?a target='_blank' class='url'>https://github.com/rust-lang/rust/pull/74726
tracing 更好�?/p>
- 文档及示例更�?/li>
- 支持库更�?/li>

金庆 2021-11-24 18:18 发表评论

Named parameters in Rust

金庆 — Thu, 18 Nov 2021 05:14:00 GMT

Named parameters in Rust

(Jin Qing's Column, Nov. 18, 2021)

There is no "named function parameters" in Rust, but there is an idiom for this case. If a function needs many parameters, we can define a type with all these parameters as fields, and implement Default trait for this type. Then we can input this type as the function parameter, with some of the fields specified and others using default.

foo(Config {
    a: 123,
    b: bool,
    ...Default::default(),
});

金庆 2021-11-18 13:14 发表评论

Rust traits act as generic constraints

金庆 — Thu, 18 Nov 2021 04:51:00 GMT

Rust traits act as generic constraints

(Jin Qing's Column, Nov. 18, 2021)

Rust traits are different from interfaces of C++/Java/Go.

See: https://stevedonovan.github.io/rustifications/2018/09/08/common-rust-traits.html

Rust traits are mechanism for adding behavior to types.

Traits have 2 modes. One is interface as Java.

Another is generic constraint. Generic functions are defined over types that implemented specific traits.

The "complie-time duck typing" in C++ templates is avoided in Rust. Rust will reject a type with quack() method as a Duck type. We must pass a type which implements Duck trait. But in Go, a type with quack() method is sufficient to be used as a Duck interface.

金庆 2021-11-18 12:51 发表评论

GLIBC_2.29 not found

金庆 — Fri, 05 Nov 2021 01:42:00 GMT

GLIBC_2.29 not found

(Jin Qing's Column, Nov. 4, 2021)

My Rust program failed when running in docker:

root@a26b49c91efb:/myapp# ldd libmyapp_py.so
./libmyapp_py.so: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.29' not found (required by ./libmyapp_py.so)

The problem is because I build in "rust:1.56", and run in "debian:buster-slim" which is quite old. Run dpkg -l libc-bin shows the libc version is 2.28:

C:\Users\jinqing01>docker run debian:buster-slim dpkg -l libc-bin
Unable to find image 'debian:buster-slim' locally
buster-slim: Pulling from library/debian
b380bbd43752: Already exists
Digest: sha256:544c93597c784cf68dbe492ef35c00de7f4f6a990955c7144a40b20d86a3475f
Status: Downloaded newer image for debian:buster-slim
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  libc-bin       2.28-10      amd64        GNU C Library: Binaries

Using the latest "debian:bookworm-slim" solved the problem.

Dockerfile:

FROM rust:1.56 as chef
RUN cargo install cargo-chef
WORKDIR /myapp
FROM chef AS planner
COPY . .
RUN cargo chef prepare --recipe-path recipe.json
FROM chef AS builder
COPY --from=planner /myapp/recipe.json recipe.json
# Build dependencies
RUN cargo chef cook --release --recipe-path recipe.json
# Build application
COPY . .
RUN cargo build --release
FROM debian:bookworm-slim AS runtime
WORKDIR /myapp
RUN apt-get update && apt-get install -y python3 python3-pip && rm -rf /var/lib/apt/lists/*
RUN pip3 install protobuf
COPY --from=builder /myapp/target/release/*.so /myapp/
COPY --from=builder /myapp/target/release/myapp /myapp/
COPY --from=builder /myapp/tests /myapp/tests
CMD ["myapp"]

金庆 2021-11-05 09:42 发表评论

Clustering provider in Orleans

金庆 — Wed, 03 Nov 2021 05:36:00 GMT

Clustering provider in Orleans

(Jin Qing's Column, Nov. 3, 2021)

When deployed to a cluster of nodes, Orleans internally implements a protocol to manage it's silos, including discovery, failure and reconfigure, which is called cluster membership management.

Orleans has clustering membership providers for: Azure, SQL server, Zookeeper.

Clustering provider is one of key aspects of silo configuration.

Orleans.Clustering.Kubernetes

OrleansContrib/Orleans.Clustering.Kubernetes is a clustering provider for running Orleans cluster on Kubernetes.

Tell silo to use Kubernetes as the Cluster Membership Provider:

var silo = new SiloBuilder()
        ...
        .UseKubeMembership()
        ...
        .Build();

Interface

UseKubeMembership() instantiates a KubeMembershipTable which implements IMembershipTable.

    public interface IMembershipTable
    {
        Task InitializeMembershipTable(bool tryInitTableVersion);
        Task DeleteMembershipTableEntries(string clusterId);
        Task CleanupDefunctSiloEntries(DateTimeOffset beforeDate);
        Task ReadRow(SiloAddress key);
        Task ReadAll();
        Task InsertRow(MembershipEntry entry, TableVersion tableVersion);
        Task UpdateRow(MembershipEntry entry, string etag, TableVersion tableVersion);
        Task UpdateIAmAlive(MembershipEntry entry);
    }

Implement

KubeMembershipTable access Kubernetes API server to read and write silo entry CRD.

InitializeMembershipTable()
- TryInitClusterVersion()
  - _kubeClient.GetNamespacedCustomObjectAsync
  - _kubeClient.CreateNamespacedCustomObjectAsync
DeleteMembershipTableEntries(string clusterId)
- _kubeClient.DeleteNamespacedCustomObjectAsync
InsertRow(...)
- _kubeClient.GetNamespacedCustomObjectAsync
- _kubeClient.ReplaceNamespacedCustomObjectAsync
- _kubeClient.CreateNamespacedCustomObjectAsync
ReadAll()
- GetClusterVersion()
  - _kubeClient.ListNamespacedCustomObjectAsync
- GetSilos()
  - _kubeClient.ListNamespacedCustomObjectAsync
ReadRow(SiloAddress key)
- _kubeClient.GetNamespacedCustomObjectAsync
UpdateIAmAlive(MembershipEntry entry)
- _kubeClient.GetNamespacedCustomObjectAsync
- _kubeClient.ReplaceNamespacedCustomObjectAsync
UpdateRow(...)
- _kubeClient.ReplaceNamespacedCustomObjectAsync
CleanupDefunctSiloEntries(DateTimeOffset beforeDate)
- _kubeClient.DeleteNamespacedCustomObjectAsync

The operators to NamespacedCustomObject are:

Delete
Get
Create
Replace
List

CRD

Two CRDs, ClusterVersion and Silo are defined in files:

ClusterVersionCRD.yaml
SiloEntryCRD.yaml

Custom resource objects are stored in etcd of Kubernetes.

金庆 2021-11-03 13:36 发表评论

Why Orleans' actor is virutal

金庆 — Tue, 02 Nov 2021 07:27:00 GMT

Why Orleans' actor is virutal

(Jin Qing's Column, Nov. 2, 2021)

Virtual Actor is a concept invented by Microsoft Orleans, which is a framework of distributed actor.

Orleans: Distributed Virtual Actors for Programmability and Scalability describes the virtual programming model.

The virtual actor is analogous to virtual memory. Virtual actors are mapped to physical arctors instances in the running servers. Virtualization of actors in Orleans has 4 facets:

Perpetual existence
- Actors always exist, virtually
- Actors can not be created or destroied explicitly
- Server failure does not affect the actors' existence
Automatic instantiation
- Activation: Orleans automatically create an actor
- A request triggers an activation if the actor doesn't exist
- Unused actors are automatically reclaimed
Location transparency
- Applications don't know where the physical actor is
- Similar to virtual memory's "paged out" and mapping
Automatic scale out
- 2 activation modes:
  - Single activation (default): Only one simultaneous actor is allowed
  - Stateless worker: Many activations of an actor are created
    - to increase throughput

Actor viruliaztion greatly simplifes the programming, since it gets rid of the burden of actor lifecycle control.

金庆 2021-11-02 15:27 发表评论

What comes after microservice?

金庆 — Fri, 29 Oct 2021 03:16:00 GMT

What comes after microservice?

(Jin Qing's Column, Oct. 25, 2021)

Reading "The Evolution of Distributed Systems on Kubernetes" from Bilgin Ibryam.

https://www.infoq.com/articles/distributed-systems-kubernetes/

What are the purpose of projects like Dapr, Istio, Knative? How can they change the world?

Modern distributed systems

The needs of distributed systems:

Business logic
Other
- Lifecycle: deploy, rollback, upgrade, scale, stop, isolate, config
- Network: connect, circuit break, retry, timeout, load balance, discover, security, trace
- Resource binding: to API, protocol, message, data format
- State: stateless, stateful, store

Monolithic architecture

enterprise service bus (ESB): not distributed

Cloud-native architecture

Kubernetes: Lifecycle

Service Mesh

Istio: Networking

Serverless

Knative: scale

Dapr

Networking, resource binding, state

Trends

Lifecycle: Kubernetes + operator
Networking: Envoy
Binding: Apache Camel
State: Cloudstate

Multi-runtime microservice

Write business logic as another runtime. Here runtime is a process?

What comes after microservice

Faas is not the best. Multi-runtime microservice maybe is.

Mecha architecture

金庆 2021-10-29 11:16 发表评论

Display Non-UTF-8 output

金庆 — Wed, 27 Oct 2021 04:22:00 GMT

Display Non-UTF-8 output

(Jin Qing's Column, Oct. 27, 2021)

Cargo build output Non-UTF-8. Use python to decode it as gbk and print.

```

C:\Users\jinqing01>python

>>> s = b'Non-UTF-8 output: \xd5\xfd\xd4\xda\xb4\xb4\xbd\xa8\xbf\xe2 E:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll.lib \xba\xcd\xb6\xd4\xcf\xf3 E:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll.exp\r\npyext.2rtvxajnfydf6uo2.rcgu.o : error LNK2019: \xce\xde\xb7\xa8\xbd\xe2\xce\xf6\xb5\xc4\xcd\xe2\xb2\xbf\xb7\xfb\xba\xc5 __imp_PyUnicode_AsUTF8\xa3\xac\xba\xaf\xca\xfd _ZN116_$LT$pyext..script..pyext..py_object_proxy..PyNonTxnStates$u20$as$u20$pyext..object..state..NonTxnStates$GT$14to_mysql_value17h5dbfad19064f6106E \xd6\xd0\xd2\xfd\xd3\xc3\xc1\xcb\xb8\xc3\xb7\xfb\xba\xc5\r\npyext.3i2r75wtstbttq2v.rcgu.o : error LNK2001: \xce\xde\xb7\xa8\xbd\xe2\xce\xf6\xb5\xc4\xcd\xe2\xb2\xbf\xb7\xfb\xba\xc5 __imp_PyUnicode_AsUTF8\r\nlibpyutil-98f7dde2ceee0f61.rlib(pyutil-98f7dde2ceee0f61.2r21sryt0zfxlscx.rcgu.o) : error LNK2001: \xce\xde\xb7\xa8\xbd\xe2\xce\xf6\xb5\xc4\xcd\xe2\xb2\xbf\xb7\xfb\xba\xc5 __imp_PyUnicode_AsUTF8\r\nE:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll : fatal error LNK1120: 1 \xb8\xf6\xce\xde\xb7\xa8\xbd\xe2\xce\xf6\xb5\xc4\xcd\xe2\xb2\xbf\xc3\xfc\xc1\xee\r\n'

>>> s.decode('gbk')

'Non-UTF-8 output: 正在创徏�?E:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll.lib 和对�?E:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll.exp\r\npyext.2rtvxajnfydf6uo2.rcgu.o : error LNK2019: 无法解析的外�?�W�号 __imp_PyUnicode_AsUTF8�Q�函�?_ZN116_$LT$pyext..script..pyext..py_object_proxy..PyNonTxnStates$u20$as$u20$pyext..object..state..NonTxnStates$GT$14to_mysql_value17h5dbfad19064f6106E 中引用了该符号\r\npyext.3i2r75wtstbttq2v.rcgu.o : error LNK2001: 无法解析的外部符�?__imp_PyUnicode_AsUTF8\r\nlibpyutil-98f7dde2ceee0f61.rlib(pyutil-98f7dde2ceee0f61.2r21sryt0zfxlscx.rcgu.o) : error LNK2001: 无法解析的外部符�?__imp_PyUnicode_AsUTF8\r\nE:\\gitlab\\myproj\\target\\debug\\deps\\pyext.dll : fatal error LNK1120: 1 个无法解析的外部命��o\r\n'

>>>

```

金庆 2021-10-27 12:22 发表评论

Advice for Rust library writers about Error

金庆 — Thu, 02 Sep 2021 03:24:00 GMT

Advice for library writers

Idioms for Rust libraries are still forming, but if your library needs to report custom errors, then you should probably define your own error type. It’s up to you whether or not to expose its representation (like ErrorKind) or keep it hidden (like ParseIntError). Regardless of how you do it, it’s usually good practice to at least provide some information about the error beyond just its String representation. But certainly, this will vary depending on use cases.

At a minimum, you should probably implement the Error trait. This will give users of your library some minimum flexibility for composing errors. Implementing the Error trait also means that users are guaranteed the ability to obtain a string representation of an error (because it requires impls for both fmt::Debug and fmt::Display).

Beyond that, it can also be useful to provide implementations of From on your error types. This allows you (the library author) and your users to compose more detailed errors. For example, csv::Error provides From impls for both io::Error and byteorder::Error.

Finally, depending on your tastes, you may also want to define a Result type alias, particularly if your library defines a single error type. This is used in the standard library for io::Result and fmt::Result.

From: Error Handling in Rust - Andrew Gallant's Blog (burntsushi.net)

金庆 2021-09-02 11:24 发表评论

How to show the first few errors of rustc

金庆 — Wed, 01 Sep 2021 02:55:00 GMT

# How to show the first few errors of rustc

(Jin Qing's Column, Sep. 1, 2021)

When using VS Code to develop Rust, "cargo check" output maybe thousands of lines.
Use "cargo check --color=always 2>&1 | head -n100" to limit the output.

1. Change powershell terminal to cmd, because powershell fails to use pipe
    * Terminal -> New Terminal to open a terminal
    * Open the dropdown list by click the down arrow of "+" on the top-left of terminal
    * Select "Command Prompt"
2. Type and run command: `cargo test 2>&1 --color always | "d:\Program Files\Git\usr\bin\head.exe" -n100`
    * You should change the path of head.exe

金庆 2021-09-01 10:55 发表评论

&'a mut self is restrictive

金庆 — Wed, 25 Aug 2021 05:32:00 GMT

# &'a mut self is restrictive

From https://github.com/pretzelhammer/rust-blog/blob/master/posts/common-rust-lifetime-misconceptions.md#5-if-it-compiles-then-my-lifetime-annotations-are-correct

```
#[derive(Debug)]
struct NumRef<'a>(&'a i32);

impl<'a> NumRef<'a> {
    // my struct is generic over 'a so that means I need to annotate
    // my self parameters with 'a too, right? (answer: no, not right)
    fn some_method(&'a mut self) {}
}

fn main() {
    let mut num_ref = NumRef(&5);
    num_ref.some_method(); // mutably borrows num_ref for the rest of its lifetime
    num_ref.some_method(); // �?/div>    println!("{:?}", num_ref); // �?/div>}
```

If we have some struct generic over 'a we almost never want to write a method with a &'a mut self receiver. 
What we're communicating to Rust is "this method will mutably borrow the struct for the entirety of the struct's lifetime". 
In practice this means Rust's borrow checker will only allow at most one call to some_method 
before the struct becomes permanently mutably borrowed and thus unusable. 
The use-cases for this are extremely rare but the code above is very easy for confused beginners to write and it compiles. 
The fix is to not add unnecessary explicit lifetime annotations and let Rust's lifetime elision rules handle it:

```
#[derive(Debug)]
struct NumRef<'a>(&'a i32);

impl<'a> NumRef<'a> {
    // no more 'a on mut self
    fn some_method(&mut self) {}

    // above line desugars to
    fn some_method_desugared<'b>(&'b mut self){}
}

fn main() {
    let mut num_ref = NumRef(&5);
    num_ref.some_method();
    num_ref.some_method(); // �?/div>    println!("{:?}", num_ref); // �?/div>}
```


金庆 2021-08-25 13:32 发表评论

Rust callback idiom

金庆 — Tue, 24 Aug 2021 02:19:00 GMT

# Rust callback idiom

Code is from: https://stackoverflow.com/questions/41081240/idiomatic-callbacks-in-rust
and
https://morestina.net/blog/793/closure-lifetimes-in-rust

```
struct Processor<'a> {
    callback: Box,
}

impl<'a> Processor<'a> {
    fn new() -> Processor<'a> {
        Processor {
            callback: Box::new(|| ()),
        }
    }

    fn set_callback(&mut self, c: impl FnMut() + 'a) {
        self.callback = Box::new(c);
    }

    fn process_events(&mut self) {
        (self.callback)();
    }
}

fn simple_callback() {
    println!("hello");
}

fn main() {
    let _ = Processor::new();
    
    let mut p = Processor {
        callback: Box::new(simple_callback),
    };
    p.process_events();
    let s = "world!".to_string();
    let callback2 = move || println!("hello {}", s);
    p.set_callback(callback2);
    p.process_events();
}
```

Note:
* "impl FnMut()" can only used in function declaration, not in struct declaration.
* dyn FnMut() is unsized, so it must be stored in Box
* set_callback(&mut self, c: impl FnMut()) need a lifetime for c to tell compiler that c outlives structure
    + rustc suggests `impl FnMut() + 'static`, but that is too restrictive
        - In most cases, we do not have a static lifetimed callback
* FnMut() is more restrictive than FnOnce(), but FnOnce() can only be called once
* set_callback(...) is a template method, because each closure has a different type

金庆 2021-08-24 10:19 发表评论

Rust variable rebinding for closure

金庆 — Sun, 22 Aug 2021 09:25:00 GMT

# Rust variable rebinding for closure

From: https://rust-unofficial.github.io/patterns/idioms/pass-var-to-closure.html

Rust closure captures variables by reference by default.
You can use "move" keyword to change to move variables.
In most cases, some variables are moved, and some are referenced.
We can rebind variables in a separate scope before move to the closure.

```
use std::rc::Rc;

let num1 = Rc::new(1);
let num2 = Rc::new(2);
let num3 = Rc::new(3);
let closure = {
    // `num1` is moved
    let num2 = num2.clone(); // `num2` is cloned
    let num3 = num3.as_ref(); // `num3` is borrowed
    move || {
        *num1 + *num2 + *num3;
    }
};
```

Or we can use additional variables to move in the same scope:
```
let num2_clone = num2.clone();
let num3_ref = num3.as_ref();
let closure = move || {
    *num1 + *num2_clone + *num3_ref
}
```

Using separate scope can reuse the variable name, which make the closure body clearer,
but need additional indent.

金庆 2021-08-22 17:25 发表评论

Rust Deref coercion example

金庆 — Sun, 22 Aug 2021 04:31:00 GMT

# Rust Deref coercion example

https://doc.rust-lang.org/std/ops/trait.Deref.html

```
use std::ops::Deref;

struct DerefExample {
    value: T
}

impl Deref for DerefExample {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}

let x = DerefExample { value: 'a' };
assert_eq!('a', *x);
```

Deref coercion can be used in newtype:
```
struct MyI32(i32)

impl Deref for MyI32 {
    type Target = i32;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}
```

金庆 2021-08-22 12:31 发表评论

Rust Error Return Check Policy

金庆 — Mon, 09 Aug 2021 09:08:00 GMT

Error Return Check Policy

Never use unwrap on Result. If the type is Err, it will panic and crash the program. The only exception is if it has already been checked for error previously or in test code.
Never use unwrap on Option for the same reason if the type is None as Result is Err.

金庆 2021-08-09 17:08 发表评论

Rust visibility

金庆 — Mon, 09 Aug 2021 05:45:00 GMT

From: Visibility and privacy - The Rust Reference (rust-lang.org)

`pub(in path)`, `pub(crate)`, `pub(super)`, and `pub(self)`

In addition to public and private, Rust allows users to declare an item as visible only within a given scope. The rules for pub restrictions are as follows:

pub(in path) makes an item visible within the provided path. path must be an ancestor module of the item whose visibility is being declared.
pub(crate) makes an item visible within the current crate.
pub(super) makes an item visible to the parent module. This is equivalent to pub(in super).
pub(self) makes an item visible to the current module. This is equivalent to pub(in self) or not using pub at all.

金庆 2021-08-09 13:45 发表评论

Why does Rust check borrow even in single thread

金庆 — Sat, 07 Aug 2021 08:05:00 GMT

# Why does Rust check borrow even in single thread

(Jin Qing's Column, Aug. 7, 2021)

The Rust book says borrow checking is to prevent data race.
But the borrow checker forbids multiply mutable borrows even in the same thread.
Is there data race in single thread?
Why does the borrow checker forbid it in the same thread?

[The Problem With Single-threaded Shared Mutability](https://manishearth.github.io/blog/2015/05/17/the-problem-with-shared-mutability/)
answers this question.

It gaves 2 cases that shared mutability causes prolem.
One is Rust enum variable, which can has different inner type.
If the inner type changed, the references to the old data would be invalidated.
Another case is Iterator invalidation that the container's change can invalidate the Iterator.

金庆 2021-08-07 16:05 发表评论

UE4 Blueprint Multiple Event BeginPlay

金庆 — Sat, 31 Jul 2021 07:19:00 GMT

# Multiple Event BeginPlay

(金庆的专�?2021.7)

How to do multiple actions on Event BeginPlay in UE4 Blueprints?

Sams-Teach-Yourself-Unreal-Engine-4-Game-Development-in-24-Hours says:
```
Q. When I try to add a second event node, BeginPlay, the Editor shows me the first one already
placed in the Event Graph. Why does this happen?

A. Some events, such as Event Tick and the BeginPlay event, can have only one instance per
Blueprint.
```

https://forums.unrealengine.com/t/do-multiple-things-on-event-begin-play/411/10
```
The Sequence node allows for a single execution pulse to trigger a series of events in order. The node may have any number of outputs, all of which get called as soon as the Sequence node receives an input. They will always get called in order, but without any delay. To a typical user, the outputs will likely appear to have been triggered simultaneously.
```

Youtube video: [How to do Multiple Actions on Event Begin Play Unreal Engine 4 Blueprints](https://www.youtube.com/watch?v=nqG-ztbs230)

金庆 2021-07-31 15:19 发表评论

Visual Studio 2019 Compiler Hangs

金庆 — Sat, 31 Jul 2021 07:16:00 GMT

# Visual Studio 2019 Compiler Hangs

(金庆的专�?2021.7)

Discovered by my colleague Shen Yichai:
```
Share a interesting MS Build bug:
For file a.cpp, enable optimization for Win64 or XSX.
The MSBuild always compiling without error and ending (infinite compile).
The PS5 (clang) does not have this issue.
```

The simplified code:
```
struct Tag
{
   int v;
};

void Goo(Tag* r, Tag* a)
{
   r->v = a->v;
}

void Foo(Tag* pos0, Tag* pos)
{
   for (int j = 0; j < 4; j++)
   {
        if (j == 0) {
            for (int i = 0; i < 8; i++) {
                Goo(pos0++, pos);
                Goo(pos0++, pos);
            }
        }
        else {
            for (int i = 0; i < 8; i++) {
                Goo(pos0++, pos);
                Goo(pos0++, pos);
            }
        }
   }
}

int main()
{
   Foo(nullptr, nullptr);
}
```

The default release configuration can build correctly.
But if "Properties -> C/C++ -> Optimization -> Whole Program optimization" (/GL) of file or project is changed to "No",
the compilation will take a long time as 5 minutes.

```
Microsoft Visual Studio Community 2019
Version 16.9.5
VisualStudio.16.Release/16.9.5+31229.75
Microsoft .NET Framework
Version 4.8.04084
```

金庆 2021-07-31 15:16 发表评论

Fbx File Format Identifier

金庆 — Sun, 30 May 2021 01:55:00 GMT

# Fbx File Format Identifier

(金庆的专�?2021.5)

Print the list of FBX file format identifiers.

FBX SDK FbxExporter can set the file format identifier which is an int parameter.
The commnet says: User does not need to specify it by default.
If not specified, plugin will detect the file format according to file suffix automatically.

FBX SDK 2020 automatically set it to the latest binary format, which can not be parsed by "Autodesk FBX Converter 2013".
We need to specify the format identifier for FBX Converter 2013.
But there is no specification of this parameter.
We use the following code to display all the valid format identifiers and their descriptions.

```
#include
#include

int main()
{
    FbxManager* myManager = FbxManager::Create();
    assert(myManager);

    FbxIOSettings* ios = FbxIOSettings::Create(myManager, IOSROOT);
    myManager->SetIOSettings(ios);

    int lFormatCount = myManager->GetIOPluginRegistry()->GetWriterFormatCount();
    for (int lFormatIndex = 0; lFormatIndex < lFormatCount; lFormatIndex++)
    {
        FbxString lDesc = myManager->GetIOPluginRegistry()->GetWriterFormatDescription(lFormatIndex);
        printf("Format index %d: %s\n", lFormatIndex, (const char*)lDesc);
    }
    return 0;
}
```

Output:
```
Format index 0: FBX binary (*.fbx)
Format index 1: FBX ascii (*.fbx)
Format index 2: FBX encrypted (*.fbx)
Format index 3: FBX 6.0 binary (*.fbx)
Format index 4: FBX 6.0 ascii (*.fbx)
Format index 5: FBX 6.0 encrypted (*.fbx)
Format index 6: AutoCAD DXF (*.dxf)
Format index 7: Alias OBJ (*.obj)
Format index 8: Collada DAE (*.dae)
Format index 9: Biovision BVH (*.bvh)
Format index 10: Motion Analysis HTR (*.htr)
Format index 11: Motion Analysis TRC (*.trc)
Format index 12: Acclaim ASF (*.asf)
Format index 13: Acclaim AMC (*.amc)
Format index 14: Vicon C3D (*.c3d)
Format index 15: Adaptive Optics AOA (*.aoa)
Format index 16: Superfluo MCD (*.mcd)
```

FBX Converter 2013 will error "File is corrupted" for files exported as *.fbx file format: -1, 0, 2, 5.
Ascii format (1, 4) and FBX 6.0 binary (3) are OK.

金庆 2021-05-30 09:55 发表评论

金庆 — Sun, 09 May 2021 12:44:00 GMT

# �W?代游戏主�?br />
原文�Q�[Ninth generation of video game consoles](https://en.wikipedia.org/wiki/Ninth_generation_of_video_game_consoles)

2020.11�Q�微�?MS) Xbox Series X/S �?Sony PlayStation 5 (PS5) 发布�Q�标志着游戏��L��q�入�W?代�?br />
和前代的 Xbox One �?PS4 相比�Q�新一代主机有可观的性能提升�Q�支持实时光�U�跟�t�，4K分��L率，目标帧率�?0�?br />内部都��用了固态硬�?SSD)。低配版没有光驱�Q�仅支持�|�络和USB�?br />
定位上要胜过��d��堂Switch和云游戏服务�?Stadia �?Amazon Luna.

## 背景

�W?代时间较�ѝ��因为摩��定律，�q�去几代一般每代�ؓ5�q�时��_��但是 MS �?Sony ��Z��中间代��?Xbox One X �?PS4 Pro.

2020.3 开始的 COVID-19 疫情影响也��C��代主机的发布延后了�?br />
## 主要��L��

### PS5

�?个机型，基本型和数字型，数字型没有光��p��便宜�Q�其他一栗��?br />PS5和PS4的游戏兼容，只有��量游戏不支持，但是可以通过 PS Now 云游戏服务玩 PS4 游戏�?br />
### Xbox Series X/S

MS 延��了双��L��模式�Q�高端的X�p�d��和低端的S�p�d��。S�p�d��没有光驱�?br />两者都支持外部存储和Xbox Live在线分发。向后兼容以前的游戏�Q�但不包括Kinect游戏�?br />MS鼓励开发商使用 Smart Delivery�Q�把Xbox One游戏升��到Xbox Series X/S�?br />
## 其他��L��

* ��d��?Switch
* 云游戏��^収ͼ�Stadia, Amazon Luna, GeForce Now

金庆 2021-05-09 20:44 发表评论

金庆 — Tue, 02 Mar 2021 04:00:00 GMT

Canvas Scaler �?�U�模�?br />
(金庆的专�?2021.3)

参考：
https://wenku.baidu.com/view/83991090336c1eb91b375db8.html

Unity Canvas 有个 Canvas Scaler �l��g�Q�用来决�?Canvas �?Scale(�~�放)倹{�?br />Scale �?X,Y,Z 3个分量，都是同一��|��卛_��各个方向上都是同倍率�~�放的�?br />它有3�U�Scale Mode�?br />
因�ؓ设计时的宽高比与目标机型宽高比不同，Canvas 需要先增减为目标高宽比�Q�然后再�~�放�?br />Canvas �~�放�q�不影响UI元素的相互位�|�，只是同比�~�放�?br />但是高宽比调整时会造成UI元素的相对位�|�变化，如宽度增大后�Q�UI元素会在宽度方向上相互散开�?br />
可以�?Unity Editor Game ��左上角分��L率下拉菜单中创徏几个低分辨率屏，用来��试屏幕大小切换�?br />��试界面可放�|?个按钮，一个锚定到左上�Q�位于左上，一个锚定到右下�Q�位于右下，不要strech�?br />
3�U�模式如下�?br />
## Constance Pixel Size

Constance Pixel Size 模式下，Scale ��L��?�?br />目标��Z��?Canvas ��是其分辨率大小�?br />因�ؓ设计时分辨率与实际分辨率不同�Q�显�C�Z��不同�?br />但是囄��和按钮的大小保持固定像素大小�?br />如果屏幕变大�Q�UI元素��׃��怺�散开�Q�变��则聚拢�?br />如果需要羃放，只能通过�E�序调节�?br />
## Scale With Screen Size

随屏�q�大��羃放�?br />该模式下有个 Reference Resolution (参考分辨率)�Q�应该设��Z��机型的分��L率�?br />在主��机型下�Q�Scale �?�Q�与设计昄��相同�?br />
https://blog.csdn.net/u011948420/article/details/112641308
2020中国�U�d��游戏质量白皮�?WeTest 报告 Android 手机 TOP300 分��L率�ؓ 2340*1080 �?31%�?br />
如果目标机型�?4680*2160�Q�则 Scale 正好�?�Q�如果目标机型�ؓ 1179*540�Q�则Scale�?.5.

一般情况下宽高比不同，此时Scale��法�?�U�，�?�U�Sceen Match Mode�Q?br />
### Match Width Or Height

匚w��宽度或高度�?br />
此时有个 Match 划动条，可以�?Width(0)..Height(1)之间�?br />如果�?�Q�匹配宽度，�?Scale 为目标屏宽与参考屏宽之比；
如果�?�Q�匹配高度，�?Scale 为目标屏高与参考屏高之比；
如果�?.5, 加权匚w��Q�则是这2个比值的�q�_��倹{�?br />
匚w��宽度�Ӟ��高度方向上会有UI扩散或聚拢�?br />匚w��高度�Ӟ��宽度方向上会有UI扩散或聚拢�?br />加权匚w��Ӟ��UI在高上扩散宽上聚拢，或者在高上聚拢宽上扩散�?br />
### Expand

增加。先增加宽或高到目标宽高比。该增加方向UI元素会散开�?br />
### Shrink

减少。先减少宽或高到目标宽高比。该减少方向UI元素会聚拢�?br />
## Constant Physical Size

固定物理大小�?br />随着4k屏的出现�Q�屏�q�DPI会很大，许多讑֤�的像素点非常��?br />同样的按钮，在高DPI下，如果固定像素大小�Q�则会非常小�Q�这旉��合用该模式�?br />

金庆 2021-03-02 12:00 发表评论

金庆 — Thu, 25 Feb 2021 02:38:00 GMT

# C#异步�Ҏ��q�回void和Task的区�?br />
(金庆的专�?2021.2)

如果异步(async关键�?�Ҏ��有返回��|��q�回�c�d��为T�Ӟ��q�回�c�d��必然�?`Task`�?br />但是如果没有�q�回��|��异步�Ҏ��的返回类型有2�U�，一个是�q�回 Task, 一个是�q�回 void�Q?br />```
    public async Task CountDownAsync(int count)
    {
        for (int i = count; i >= 0; i--)
        {
            await Task.Delay(1000);
        }
    }

    public async void CountDown(int count)
    {
        for (int i = count; i >= 0; i--)
        {
            await Task.Delay(1000);
        }
    }
```

调用�Ӟ��如果�q�回 Task, 但返回��D��忽略�Ӟ��VS 会用�l�色波浪�U�警告：
```
    CountDownAsync(3);
    ~~~~~~~~~~~~~~~~~
```

信息为：
```
(awaitable) Task AsyncExample.CountDownAsync(int count)

Usage:
await CountDownAsync(...);

Because this call is not awaited, execution of the current method continues before the call is completed. Consider applying the 'await' operator to the result of the call.
```

中文为：
```
CS4014:�׃��此调用不会等待，因此在此调用完成之前��会�l�箋执行当前�Ҏ��。请考虑��?await"�q�算�W�应用于调用�l�果�?br />```

��d�� await 后就正常了：
```
    await CountDownAsync(3);
```

如果调用者不是一个异步方法，因�ؓ只有在异步方法中才可以��?await,
或者�ƈ不想在此�{�待�Q�如惛_��时执行多�?CountDownAsync(),
��׃��能应�?await 来消除警告�?br />
此时可以改用 void �q�回值的版本�Q?br />```
void Test()
{
    ...
    CountDown(3);
    CountDown(3);
    ...
}

async void CountDown(int count)
{
    for (int i = count; i >= 0; i--)
    {
        await Task.Delay(1000);
    }
}
```

> Never call `async Task` methods without also awaiting on the returned Task. If you don’t want to wait for the async behaviour to complete, you should call an `async void` method instead.

摘自�Q�http://www.stevevermeulen.com/index.php/2017/09/using-async-await-in-unity3d-2017/

CountDown() 可以直接调用 CountDownAsync() 实现�Q?br />```
async void CountDown(int count)
{
    await CountDownAsync(count);
}
```

使用下划�U�变量忽略异步方法的�q�回��g��可以消除警告�Q?br />```
void Test()
{
    ...
    _ = CountDownAsync(3);
    _ = CountDownAsync(3);
    ...
}
```

但是�q�样同时也会忽略 CountDownAsync() 中的异常。如以下异常会被忽略�?br />
```
void Test()
{
    ...
    _ = CountDownAsync(3);
    ...
}

async Task CountDownAsync(int count)
{
    for (int i = count; i >= 0; i--)
    {
        await Task.Delay(1000);
    }
    throw new Exception();
}
```

如果是调用返�?void 的异步方法，Unity 会报错：
```
Exception: Exception of type 'System.Exception' was thrown.
```

## �?Async 后缀的说�?br />
```
You could say that the Async suffix convention is to communicate to the API user that the method is awaitable. For a method to be awaitable, it must return Task for a void, or Task for a value-returning method, which means only the latter can be suffixed with Async.
```

摘自�Q�https://stackoverflow.com/questions/15951774

grpc 生成的代码中�Q�异步请求返回了一�?AsyncCall 对象�Q�AsyncCall 实现�?GetAwaiter() 接口�Q?br />```
      public virtual grpc::AsyncUnaryCall GetFeatureAsync(global::Routeguide.Point request, ...)
```

可以�q�样调用�q�等待：
```
    var resp = await client.GetFeatureAsync(req);
```

虽然�q�回�c�d��不是`Task<>`, 但是可等待，所以添加了 Async 后缀�?br />

金庆 2021-02-25 10:38 发表评论

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How are dtLinks created in NavMesh

How are dtLinks created in NavMesh

dtLink

How link is used

fields of dtLink

How are links created

1. Connect internal links

2. Base off-mesh connections

3. Connect external off-mesn links within this tile

4. Connect with layers in current tile

5. Connect with neighbour tiles

Reference

C++ parameter passing rules

C++ parameter passing rules

Implementation of user data in cursive::Cursive

Implementation of user data in cursive::Cursive

Naming Conventions for Accessors

Naming Conventions for Accessors

Rust sometimes needs manual type annotation

Rust sometimes needs manual type annotation

Fix recastnavigation contour error

ix recastnavigation contour error

How to work around rustup-init failure

Closure as the function parameter

Closure as the function parameter

Deadlock detection must not run as tokio task

deadlock detection must not run as tokio task

TortoiseGit is OK but GitExtensions fails

TortoiseGit is OK but GitExtensions fails

Tracing usage

Tracing usage

Dependencies

main.rs

log.rs

log_filter.txt

Example

Try tracing

Try tracing

Usage on github

Usage of RUST_LOG.

Usage on crates.io

Document

Code examples

Write to file

Dynamic level

Filters and Layers

Reload from config file

How to new a Subscriber with tracing-subscriber

Box doesn't implement the trait

minikube DNS fails after SRV query

DeathVoteExpirationTimeout in Orleans

How to delete local branches of GitExtension

�����日志 slog �Ҏ�� tracing

�����日志 slog �Ҏ�� tracing

Named parameters in Rust

Named parameters in Rust

Rust traits act as generic constraints

Rust traits act as generic constraints

GLIBC_2.29 not found

GLIBC_2.29 not found

Clustering provider in Orleans

Clustering provider in Orleans

Orleans.Clustering.Kubernetes

Interface

Implement

CRD

Why Orleans' actor is virutal

Why Orleans' actor is virutal

What comes after microservice?

What comes after microservice?

Modern distributed systems

Monolithic architecture

Cloud-native architecture

Service Mesh

Serverless

Dapr

Trends

Multi-runtime microservice

What comes after microservice

`dtLink`

fields of `dtLink`

��日志 slog �Ҏ�� tracing

��日志 slog �Ҏ�� tracing

`pub(in path)`, `pub(crate)`, `pub(super)`, and `pub(self)`