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<main>
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<h1 id="使用-tracing-输出自定义的-rust-日志"><a class="header" href="#使用-tracing-输出自定义的-rust-日志">使用 tracing 输出自定义的 Rust 日志</a></h1>
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<p>在 <a href="https://docs.rs/crate/tracing/latest">tracing</a> 包出来前，Rust 的日志也就 <code>log</code> 有一战之力，但是 <code>log</code> 的功能相对来说还是简单一些。在大名鼎鼎的 tokio 开发团队推出 <code>tracing</code> 后，我现在坚定的认为 <code>tracing</code> 就是未来！</p>
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<blockquote>
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<p>截至目前，rust编译器团队、GraphQL 都在使用 tracing，而且 tokio 在密谋一件大事：基于 tracing 开发一套终端交互式 debug 工具: <a href="https://github.com/tokio-rs/console">console</a>！</p>
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</blockquote>
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<p>基于这种坚定的信仰，我们决定将公司之前使用的 <code>log</code> 包替换成 <code>tracing</code> ，但是有一个问题：后者提供的 JSON logger 总感觉不是那个味儿。这意味着，对于程序员来说，最快乐的时光又要到来了：定制自己的开发工具。</p>
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<p>好了，闲话少说，下面我们一起来看看该如何构建自己的 logger，以及深入了解 tracing 的一些原理，当然你也可以只选择来凑个热闹，总之，开始吧！</p>
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<h2 id="打地基1"><a class="header" href="#打地基1">打地基(1)</a></h2>
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<p>首先，使用 <code>cargo new --bin test-tracing</code> 创建一个新的二进制类型( binary )的项目。</p>
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<p>然后引入以下依赖：</p>
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<pre><code class="language-toml"># in cargo.toml
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[dependencies]
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serde_json = "1"
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tracing = "0.1"
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|
|
tracing-subscriber = "0.3"
|
|
|
</code></pre>
|
|
|
<p>其中 <code>tracing-subscriber</code> 用于订阅正在发生的日志、监控事件，然后可以对它们进行进一步的处理。<code>serde_json</code> 可以帮我们更好的处理格式化的 JSON，毕竟咱们要解决的问题就来自于 JSON logger。</p>
|
|
|
<p>下面来实现一个基本功能：设置自定义的 logger，并使用 <code>info!</code> 来打印一行日志。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021">// in examples/figure_0/main.rs
|
|
|
|
|
|
use tracing::info;
|
|
|
use tracing_subscriber::prelude::*;
|
|
|
|
|
|
mod custom_layer;
|
|
|
use custom_layer::CustomLayer;
|
|
|
|
|
|
fn main() {
|
|
|
// 设置 `tracing-subscriber` 对 tracing 数据的处理方式
|
|
|
tracing_subscriber::registry().with(CustomLayer).init();
|
|
|
|
|
|
// 打印一条简单的日志。用 `tracing` 的行话来说，`info!` 将创建一个事件
|
|
|
info!(a_bool = true, answer = 42, message = "first example");
|
|
|
}</code></pre>
|
|
|
<p>大家会发现，上面引入了一个模块 <code>custom_layer</code>， 下面从该模块开始，来实现我们的自定义 logger。首先，<code>tracing-subscriber</code> 提供了一个特征 <a href="https://docs.rs/tracing-subscriber/0.3/tracing_subscriber/layer/trait.Layer.html"><code>Layer</code></a> 专门用于处理 <code>tracing</code> 的各种事件( span, event )。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_0/custom_layer.rs
|
|
|
|
|
|
use tracing_subscriber::Layer;
|
|
|
|
|
|
pub struct CustomLayer;
|
|
|
|
|
|
impl<S> Layer<S> for CustomLayer where S: tracing::Subscriber {}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>由于还没有填入任何代码，运行该示例比你打的水漂还无力 - 毫无效果。</p>
|
|
|
<h2 id="捕获事件"><a class="header" href="#捕获事件">捕获事件</a></h2>
|
|
|
<p>在 <code>tracing</code> 中，当 <code>info!</code>、<code>error!</code> 等日志宏被调用时，就会产生一个相应的<a href="https://docs.rs/tracing/0.1/tracing/event/struct.Event.html">事件 Event</a>。</p>
|
|
|
<p>而我们首先，就要为之前的 <code>Layer</code> 特征实现 <code>on_event</code> 方法。</p>
|
|
|
<pre class="playground"><code class="language-rust editable edition2021">// in examples/figure_0/custom_layer.rs
|
|
|
|
|
|
where
|
|
|
S: tracing::Subscriber,
|
|
|
{
|
|
|
fn on_event(
|
|
|
&self,
|
|
|
event: &tracing::Event<'_>,
|
|
|
_ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
println!("Got event!");
|
|
|
println!(" level={:?}", event.metadata().level());
|
|
|
println!(" target={:?}", event.metadata().target());
|
|
|
println!(" name={:?}", event.metadata().name());
|
|
|
for field in event.fields() {
|
|
|
println!(" field={}", field.name());
|
|
|
}
|
|
|
}
|
|
|
}</code></pre>
|
|
|
<p>从代码中可以看出，我们打印了事件中包含的事件名、日志等级以及事件发生的代码路径。运行后，可以看到以下输出:</p>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_1
|
|
|
|
|
|
Got event!
|
|
|
level=Level(Info)
|
|
|
target="figure_1"
|
|
|
name="event examples/figure_1/main.rs:10"
|
|
|
field=a_bool
|
|
|
field=answer
|
|
|
field=message
|
|
|
</code></pre>
|
|
|
<p>但是奇怪的是，我们无法通过 API 来获取到具体的 <code>field</code> 值。还有就是，上面的输出还不是 JSON 格式。</p>
|
|
|
<p>现在问题来了，要创建自己的 logger，不能获取 <code>filed</code> 显然是不靠谱的。</p>
|
|
|
<h3 id="访问者模式"><a class="header" href="#访问者模式">访问者模式</a></h3>
|
|
|
<p>在设计上，<code>tracing</code> 作出了一个选择：永远不会自动存储产生的事件数据( spans, events )。如果我们要获取这些数据，就必须自己手动存储。</p>
|
|
|
<p>解决办法就是使用访问者模式(Visitor Pattern)：手动实现 <code>Visit</code> 特征去获取事件中的值。<code>Visit</code> 为每个 <code>tracing</code> 可以处理的类型都提供了对应的 <code>record_X</code> 方法。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_2/custom_layer.rs
|
|
|
|
|
|
struct PrintlnVisitor;
|
|
|
|
|
|
impl tracing::field::Visit for PrintlnVisitor {
|
|
|
fn record_f64(&mut self, field: &tracing::field::Field, value: f64) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_i64(&mut self, field: &tracing::field::Field, value: i64) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_u64(&mut self, field: &tracing::field::Field, value: u64) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_bool(&mut self, field: &tracing::field::Field, value: bool) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_str(&mut self, field: &tracing::field::Field, value: &str) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_error(
|
|
|
&mut self,
|
|
|
field: &tracing::field::Field,
|
|
|
value: &(dyn std::error::Error + 'static),
|
|
|
) {
|
|
|
println!(" field={} value={}", field.name(), value)
|
|
|
}
|
|
|
|
|
|
fn record_debug(&mut self, field: &tracing::field::Field, value: &dyn std::fmt::Debug) {
|
|
|
println!(" field={} value={:?}", field.name(), value)
|
|
|
}
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>然后在之前的 <code>on_event</code> 中来使用这个新的访问者： <code>event.record(&mut visitor)</code> 可以访问其中的所有值。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_2/custom_layer.rs
|
|
|
|
|
|
fn on_event(
|
|
|
&self,
|
|
|
event: &tracing::Event<'_>,
|
|
|
_ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
println!("Got event!");
|
|
|
println!(" level={:?}", event.metadata().level());
|
|
|
println!(" target={:?}", event.metadata().target());
|
|
|
println!(" name={:?}", event.metadata().name());
|
|
|
let mut visitor = PrintlnVisitor;
|
|
|
event.record(&mut visitor);
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>这段代码看起来有模有样，来运行下试试：</p>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_2
|
|
|
|
|
|
Got event!
|
|
|
level=Level(Info)
|
|
|
target="figure_2"
|
|
|
name="event examples/figure_2/main.rs:10"
|
|
|
field=a_bool value=true
|
|
|
field=answer value=42
|
|
|
field=message value=first example
|
|
|
</code></pre>
|
|
|
<p>Bingo ! 一切完美运行 ！</p>
|
|
|
<h3 id="构建-json-logger"><a class="header" href="#构建-json-logger">构建 JSON logger</a></h3>
|
|
|
<p>目前为止，离我们想要的 JSON logger 只差一步了。下面来实现一个 <code>JsonVisitor</code> 替代之前的 <code>PrintlnVisitor</code> 用于构建一个 JSON 对象。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_3/custom_layer.rs
|
|
|
|
|
|
|
|
|
impl<'a> tracing::field::Visit for JsonVisitor<'a> {
|
|
|
fn record_f64(&mut self, field: &tracing::field::Field, value: f64) {
|
|
|
self.0
|
|
|
.insert(field.name().to_string(), serde_json::json!(value));
|
|
|
}
|
|
|
|
|
|
fn record_i64(&mut self, field: &tracing::field::Field, value: i64) {
|
|
|
self.0
|
|
|
.insert(field.name().to_string(), serde_json::json!(value));
|
|
|
}
|
|
|
|
|
|
fn record_u64(&mut self, field: &tracing::field::Field, value: u64) {
|
|
|
self.0
|
|
|
.insert(field.name().to_string(), serde_json::json!(value));
|
|
|
}
|
|
|
|
|
|
fn record_bool(&mut self, field: &tracing::field::Field, value: bool) {
|
|
|
self.0
|
|
|
.insert(field.name().to_string(), serde_json::json!(value));
|
|
|
}
|
|
|
|
|
|
fn record_str(&mut self, field: &tracing::field::Field, value: &str) {
|
|
|
self.0
|
|
|
.insert(field.name().to_string(), serde_json::json!(value));
|
|
|
}
|
|
|
|
|
|
fn record_error(
|
|
|
&mut self,
|
|
|
field: &tracing::field::Field,
|
|
|
value: &(dyn std::error::Error + 'static),
|
|
|
) {
|
|
|
self.0.insert(
|
|
|
field.name().to_string(),
|
|
|
serde_json::json!(value.to_string()),
|
|
|
);
|
|
|
}
|
|
|
|
|
|
fn record_debug(&mut self, field: &tracing::field::Field, value: &dyn std::fmt::Debug) {
|
|
|
self.0.insert(
|
|
|
field.name().to_string(),
|
|
|
serde_json::json!(format!("{:?}", value)),
|
|
|
);
|
|
|
}
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_3/custom_layer.rs
|
|
|
|
|
|
fn on_event(
|
|
|
&self,
|
|
|
event: &tracing::Event<'_>,
|
|
|
_ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
// Covert the values into a JSON object
|
|
|
let mut fields = BTreeMap::new();
|
|
|
let mut visitor = JsonVisitor(&mut fields);
|
|
|
event.record(&mut visitor);
|
|
|
|
|
|
// Output the event in JSON
|
|
|
let output = serde_json::json!({
|
|
|
"target": event.metadata().target(),
|
|
|
"name": event.metadata().name(),
|
|
|
"level": format!("{:?}", event.metadata().level()),
|
|
|
"fields": fields,
|
|
|
});
|
|
|
println!("{}", serde_json::to_string_pretty(&output).unwrap());
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>继续运行:</p>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_3
|
|
|
|
|
|
{
|
|
|
"fields": {
|
|
|
"a_bool": true,
|
|
|
"answer": 42,
|
|
|
"message": "first example"
|
|
|
},
|
|
|
"level": "Level(Info)",
|
|
|
"name": "event examples/figure_3/main.rs:10",
|
|
|
"target": "figure_3"
|
|
|
}
|
|
|
</code></pre>
|
|
|
<p>终于，我们实现了自己的 logger，并且成功地输出了一条 JSON 格式的日志。并且新实现的 <code>Layer</code> 就可以添加到 <code>tracing-subscriber</code> 中用于记录日志事件。</p>
|
|
|
<p>下面再来一起看看如何使用<code>tracing</code> 提供的 <code>period-of-time spans</code> 为日志增加更详细的上下文信息。</p>
|
|
|
<h3 id="何为-span"><a class="header" href="#何为-span">何为 span</a></h3>
|
|
|
<p>在之前我们多次提到 span 这个词，但是何为 span？</p>
|
|
|
<p>不知道大家知道分布式追踪不？在分布式系统中每一个请求从开始到返回，会经过多个服务，这条请求路径被称为请求跟踪链路( trace )，可以看出，一条链路是由多个部分组成，我们可以简单的把其中一个部分认为是一个 span。</p>
|
|
|
<p>跟 log 是对某个时间点的记录不同，span 记录的是一个时间段。当程序开始执行一系列任务时，span 就会开始，当这一系列任务结束后，span 也随之结束。</p>
|
|
|
<p>由此可见，tracing 其实不仅仅是一个日志库，它还是一个分布式追踪的库，可以帮助我们采集信息，然后上传给 jaeger 等分布式追踪平台，最终实现对指定应用程序的监控。</p>
|
|
|
<p>在理解后，再来看看该如何为自定义的 logger 实现 spans。</p>
|
|
|
<h3 id="打地基2"><a class="header" href="#打地基2">打地基(2)</a></h3>
|
|
|
<p>先来创建一个外部 span 和一个内部 span，从概念上来说，spans 和 events 创建的东东类似以下嵌套结构：</p>
|
|
|
<ul>
|
|
|
<li>进入外部 span
|
|
|
<ul>
|
|
|
<li>进入内部 span
|
|
|
<ul>
|
|
|
<li>事件已创建，内部 span 是它的父 span，外部 span 是它的祖父 span</li>
|
|
|
</ul>
|
|
|
</li>
|
|
|
<li>结束内部 span</li>
|
|
|
</ul>
|
|
|
</li>
|
|
|
<li>结束外部 span</li>
|
|
|
</ul>
|
|
|
<blockquote>
|
|
|
<p>有些同学可能还是不太理解，你就把 span 理解成为监控埋点，进入 span == 埋点开始，结束 span == 埋点结束</p>
|
|
|
</blockquote>
|
|
|
<p>在下面的代码中，当使用 <code>span.enter()</code> 创建的 span 超出作用域时，将自动退出：根据 <code>Drop</code> 特征触发的顺序，<code>inner_span</code> 将先退出，然后才是 <code>outer_span</code> 的退出。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021">// in examples/figure_5/main.rs
|
|
|
|
|
|
use tracing::{debug_span, info, info_span};
|
|
|
use tracing_subscriber::prelude::*;
|
|
|
|
|
|
mod custom_layer;
|
|
|
use custom_layer::CustomLayer;
|
|
|
|
|
|
fn main() {
|
|
|
tracing_subscriber::registry().with(CustomLayer).init();
|
|
|
|
|
|
let outer_span = info_span!("outer", level = 0);
|
|
|
let _outer_entered = outer_span.enter();
|
|
|
|
|
|
let inner_span = debug_span!("inner", level = 1);
|
|
|
let _inner_entered = inner_span.enter();
|
|
|
|
|
|
info!(a_bool = true, answer = 42, message = "first example");
|
|
|
}</code></pre>
|
|
|
<p>再回到事件处理部分，通过使用 <code>examples/figure_0/main.rs</code> 我们能获取到事件的父 span，当然，前提是它存在。但是在实际场景中，直接使用 <code>ctx.event_scope(event)</code> 来迭代所有 span 会更加简单好用。</p>
|
|
|
<p>注意，这种迭代顺序类似于栈结构，以上面的代码为例，先被迭代的是 <code>inner_span</code>，然后才是 <code>outer_span</code>。</p>
|
|
|
<p>当然，如果你不想以类似于出栈的方式访问，还可以使用 <code>scope.from_root()</code> 直接反转，此时的访问将从最外层开始： <code>outer -> innter</code>。</p>
|
|
|
<p>对了，为了使用 <code>ctx.event_scope()</code>，我们的订阅者还需实现 <code>LookupRef</code>。提前给出免责声明：这里的实现方式有些诡异，大家可能难以理解，但是..我们其实也无需理解，只要这么用即可。</p>
|
|
|
<blockquote>
|
|
|
<p>译者注：这里用到了高阶生命周期 HRTB( Higher Ranke Trait Bounds ) 的概念，一般的读者无需了解，感兴趣的可以看看(这里)[https://doc.rust-lang.org/nomicon/hrtb.html]</p>
|
|
|
</blockquote>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_5/custom_layer.rs
|
|
|
|
|
|
impl<S> Layer<S> for CustomLayer
|
|
|
where
|
|
|
S: tracing::Subscriber,
|
|
|
// 好可怕! 还好我们不需要理解它，只要使用即可
|
|
|
S: for<'lookup> tracing_subscriber::registry::LookupSpan<'lookup>,
|
|
|
{
|
|
|
fn on_event(&self, event: &tracing::Event<'_>, ctx: tracing_subscriber::layer::Context<'_, S>) {
|
|
|
// 父 span
|
|
|
let parent_span = ctx.event_span(event).unwrap();
|
|
|
println!("parent span");
|
|
|
println!(" name={}", parent_span.name());
|
|
|
println!(" target={}", parent_span.metadata().target());
|
|
|
|
|
|
println!();
|
|
|
|
|
|
// 迭代范围内的所有的 spans
|
|
|
let scope = ctx.event_scope(event).unwrap();
|
|
|
for span in scope.from_root() {
|
|
|
println!("an ancestor span");
|
|
|
println!(" name={}", span.name());
|
|
|
println!(" target={}", span.metadata().target());
|
|
|
}
|
|
|
}
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>运行下看看效果:</p>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_5
|
|
|
|
|
|
parent span
|
|
|
name=inner
|
|
|
target=figure_5
|
|
|
|
|
|
an ancestor span
|
|
|
name=outer
|
|
|
target=figure_5
|
|
|
an ancestor span
|
|
|
name=inner
|
|
|
target=figure_5
|
|
|
</code></pre>
|
|
|
<p>细心的同学可能会发现，这里怎么也没有 field 数据？没错，而且恰恰是这些 field 包含的数据才让日志和监控有意义。那我们可以像之前一样，使用访问器 Visitor 来解决吗？</p>
|
|
|
<h3 id="span-的数据在哪里"><a class="header" href="#span-的数据在哪里">span 的数据在哪里</a></h3>
|
|
|
<p>答案是：No。因为 <code>ctx.event_scope </code> 返回的东东没有任何办法可以访问其中的字段。</p>
|
|
|
<p>不知道大家还记得我们为何之前要使用访问器吗？很简单，因为 <code>tracing</code> 默认不会去存储数据，既然如此，那 <code>span</code> 这种跨了某个时间段的，就更不可能去存储数据了。</p>
|
|
|
<p>现在只能看看 <code>Layer</code> 特征有没有提供其它的方法了，哦呦，发现了一个 <code>on_new_span</code>，从名字可以看出，该方法是在 <code>span</code> 创建时调用的。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_6/custom_layer.rs
|
|
|
|
|
|
impl<S> Layer<S> for CustomLayer
|
|
|
where
|
|
|
S: tracing::Subscriber,
|
|
|
S: for<'lookup> tracing_subscriber::registry::LookupSpan<'lookup>,
|
|
|
{
|
|
|
fn on_new_span(
|
|
|
&self,
|
|
|
attrs: &tracing::span::Attributes<'_>,
|
|
|
id: &tracing::span::Id,
|
|
|
ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
let span = ctx.span(id).unwrap();
|
|
|
println!("Got on_new_span!");
|
|
|
println!(" level={:?}", span.metadata().level());
|
|
|
println!(" target={:?}", span.metadata().target());
|
|
|
println!(" name={:?}", span.metadata().name());
|
|
|
|
|
|
// Our old friend, `println!` exploration.
|
|
|
let mut visitor = PrintlnVisitor;
|
|
|
attrs.record(&mut visitor);
|
|
|
}
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_6
|
|
|
Got on_new_span!
|
|
|
level=Level(Info)
|
|
|
target="figure_7"
|
|
|
name="outer"
|
|
|
field=level value=0
|
|
|
Got on_new_span!
|
|
|
level=Level(Debug)
|
|
|
target="figure_7"
|
|
|
name="inner"
|
|
|
field=level value=1
|
|
|
</code></pre>
|
|
|
<p>芜湖! 我们的数据回来了！但是这里有一个隐患：只能在创建的时候去访问数据。如果仅仅是为了记录 spans，那没什么大问题，但是如果我们随后需要记录事件然后去尝试访问之前的 span 呢？此时 span 的数据已经不存在了！</p>
|
|
|
<p>如果 <code>tracing</code> 不能存储数据，那我们这些可怜的开发者该怎么办？</p>
|
|
|
<h3 id="自己存储-span-数据"><a class="header" href="#自己存储-span-数据">自己存储 span 数据</a></h3>
|
|
|
<p>何为一个优秀的程序员？能偷懒的时候绝不多动半跟手指，但是需要勤快的时候，也是自己动手丰衣足食的典型。</p>
|
|
|
<p>因此，既然 <code>tracing</code> 不支持，那就自己实现吧。先确定一个目标：捕获 span 的数据，然后存储在某个地方以便后续访问。</p>
|
|
|
<p>好在 <code>tracing-subscriber</code> 提供了扩展 extensions 的方式，可以让我们轻松地存储自己的数据，该扩展甚至可以跟每一个 span 联系在一起！</p>
|
|
|
<p>虽然我们可以把之前见过的 <code>BTreeMap<String, serde_json::Value></code> 存在扩展中，但是由于扩展数据是被 registry 中的所有layers 所共享的，因此出于私密性的考虑，还是只保存私有字段比较合适。这里使用一个 newtype 模式来创建新的类型:</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_8/custom_layer.rs
|
|
|
|
|
|
#[derive(Debug)]
|
|
|
struct CustomFieldStorage(BTreeMap<String, serde_json::Value>);
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>每次发现一个新的 span 时，都基于它来构建一个 JSON 对象，然后将其存储在扩展数据中。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_8/custom_layer.rs
|
|
|
|
|
|
fn on_new_span(
|
|
|
&self,
|
|
|
attrs: &tracing::span::Attributes<'_>,
|
|
|
id: &tracing::span::Id,
|
|
|
ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
// 基于 field 值来构建我们自己的 JSON 对象
|
|
|
let mut fields = BTreeMap::new();
|
|
|
let mut visitor = JsonVisitor(&mut fields);
|
|
|
attrs.record(&mut visitor);
|
|
|
|
|
|
// 使用之前创建的 newtype 包裹下
|
|
|
let storage = CustomFieldStorage(fields);
|
|
|
|
|
|
// 获取内部 span 数据的引用
|
|
|
let span = ctx.span(id).unwrap();
|
|
|
// 获取扩展，用于存储我们的 span 数据
|
|
|
let mut extensions = span.extensions_mut();
|
|
|
// 存储！
|
|
|
extensions.insert::<CustomFieldStorage>(storage);
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>这样，未来任何时候我们都可以取到该 span 包含的数据( 例如在 <code>on_event</code> 方法中 )。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_8/custom_layer.rs
|
|
|
|
|
|
fn on_event(&self, event: &tracing::Event<'_>, ctx: tracing_subscriber::layer::Context<'_, S>) {
|
|
|
let scope = ctx.event_scope(event).unwrap();
|
|
|
println!("Got event!");
|
|
|
for span in scope.from_root() {
|
|
|
let extensions = span.extensions();
|
|
|
let storage = extensions.get::<CustomFieldStorage>().unwrap();
|
|
|
println!(" span");
|
|
|
println!(" target={:?}", span.metadata().target());
|
|
|
println!(" name={:?}", span.metadata().name());
|
|
|
println!(" stored fields={:?}", storage);
|
|
|
}
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<h3 id="功能齐全的-json-logger"><a class="header" href="#功能齐全的-json-logger">功能齐全的 JSON logger</a></h3>
|
|
|
<p>截至目前，我们已经学了不少东西，下面来利用这些知识实现最后的 JSON logger。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_9/custom_layer.rs
|
|
|
|
|
|
fn on_event(&self, event: &tracing::Event<'_>, ctx: tracing_subscriber::layer::Context<'_, S>) {
|
|
|
// All of the span context
|
|
|
let scope = ctx.event_scope(event).unwrap();
|
|
|
let mut spans = vec![];
|
|
|
for span in scope.from_root() {
|
|
|
let extensions = span.extensions();
|
|
|
let storage = extensions.get::<CustomFieldStorage>().unwrap();
|
|
|
let field_data: &BTreeMap<String, serde_json::Value> = &storage.0;
|
|
|
spans.push(serde_json::json!({
|
|
|
"target": span.metadata().target(),
|
|
|
"name": span.name(),
|
|
|
"level": format!("{:?}", span.metadata().level()),
|
|
|
"fields": field_data,
|
|
|
}));
|
|
|
}
|
|
|
|
|
|
// The fields of the event
|
|
|
let mut fields = BTreeMap::new();
|
|
|
let mut visitor = JsonVisitor(&mut fields);
|
|
|
event.record(&mut visitor);
|
|
|
|
|
|
// And create our output
|
|
|
let output = serde_json::json!({
|
|
|
"target": event.metadata().target(),
|
|
|
"name": event.metadata().name(),
|
|
|
"level": format!("{:?}", event.metadata().level()),
|
|
|
"fields": fields,
|
|
|
"spans": spans,
|
|
|
});
|
|
|
println!("{}", serde_json::to_string_pretty(&output).unwrap());
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<pre><code class="language-properties">$ cargo run --example figure_9
|
|
|
|
|
|
{
|
|
|
"fields": {
|
|
|
"a_bool": true,
|
|
|
"answer": 42,
|
|
|
"message": "first example"
|
|
|
},
|
|
|
"level": "Level(Info)",
|
|
|
"name": "event examples/figure_9/main.rs:16",
|
|
|
"spans": [
|
|
|
{
|
|
|
"fields": {
|
|
|
"level": 0
|
|
|
},
|
|
|
"level": "Level(Info)",
|
|
|
"name": "outer",
|
|
|
"target": "figure_9"
|
|
|
},
|
|
|
{
|
|
|
"fields": {
|
|
|
"level": 1
|
|
|
},
|
|
|
"level": "Level(Debug)",
|
|
|
"name": "inner",
|
|
|
"target": "figure_9"
|
|
|
}
|
|
|
],
|
|
|
"target": "figure_9"
|
|
|
}
|
|
|
</code></pre>
|
|
|
<p>嗯，完美。</p>
|
|
|
<h3 id="等等你说功能齐全"><a class="header" href="#等等你说功能齐全">等等，你说功能齐全？</a></h3>
|
|
|
<p>上面的代码在发布到生产环境后，依然运行地相当不错，但是我发现还缺失了一个功能: span 在创建之后，依然要能记录数据。</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_10/main.rs
|
|
|
|
|
|
let outer_span = info_span!("outer", level = 0, other_field = tracing::field::Empty);
|
|
|
let _outer_entered = outer_span.enter();
|
|
|
// Some code...
|
|
|
outer_span.record("other_field", &7);
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>如果基于之前的代码运行上面的代码，我们将不会记录 <code>other_field</code>，因为该字段在收到 <code>on_new_span</code> 事件时，还不存在。</p>
|
|
|
<p>对此，<code>Layer</code> 提供了 <code>on_record</code> 方法：</p>
|
|
|
<pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>// in examples/figure_10/custom_layer.rs
|
|
|
|
|
|
fn on_record(
|
|
|
&self,
|
|
|
id: &tracing::span::Id,
|
|
|
values: &tracing::span::Record<'_>,
|
|
|
ctx: tracing_subscriber::layer::Context<'_, S>,
|
|
|
) {
|
|
|
// 获取正在记录数据的 span
|
|
|
let span = ctx.span(id).unwrap();
|
|
|
|
|
|
// 获取数据的可变引用，该数据是在 on_new_span 中创建的
|
|
|
let mut extensions_mut = span.extensions_mut();
|
|
|
let custom_field_storage: &mut CustomFieldStorage =
|
|
|
extensions_mut.get_mut::<CustomFieldStorage>().unwrap();
|
|
|
let json_data: &mut BTreeMap<String, serde_json::Value> = &mut custom_field_storage.0;
|
|
|
|
|
|
// 使用我们的访问器老朋友
|
|
|
let mut visitor = JsonVisitor(json_data);
|
|
|
values.record(&mut visitor);
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre>
|
|
|
<p>终于，在最后，我们拥有了一个功能齐全的自定义的 JSON logger，大家快去尝试下吧。当然，你也可以根据自己的需求来定制专属于你的 logger，毕竟方法是一通百通的。</p>
|
|
|
<blockquote>
|
|
|
<p>在以下 github 仓库，可以找到完整的代码: https://github.com/bryanburgers/tracing-blog-post</p>
|
|
|
<p>本文由 Rustt 提供翻译
|
|
|
原文链接: https://github.com/studyrs/Rustt/blob/main/Articles/%5B2022-04-07%5D%20在%20Rust%20中使用%20tracing%20自定义日志.md</p>
|
|
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</blockquote>
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