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<ol class="chapter"><li class="chapter-item affix "><a href="../about-book.html">关于本书</a></li><li class="chapter-item affix "><a href="../into-rust.html">进入 Rust 编程世界</a></li><li class="chapter-item affix "><a href="../first-try/sth-you-should-not-do.html">避免从入门到放弃</a></li><li class="chapter-item affix "><a href="../community.html">社区和锈书</a></li><li class="spacer"></li><li class="chapter-item affix "><a href="../some-thoughts.html">Xobserve: 一切皆可观测</a></li><li class="chapter-item affix "><a href="../beat-ai.html">BeatAI: 工程师 AI 入门圣经</a></li><li class="chapter-item affix "><li class="part-title">Rust 语言基础学习</li><li class="spacer"></li><li class="chapter-item "><a href="../first-try/intro.html"><strong aria-hidden="true">1.</strong> 寻找牛刀，以便小试</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../first-try/installation.html"><strong aria-hidden="true">1.1.</strong> 安装 Rust 环境</a></li><li class="chapter-item "><a href="../first-try/editor.html"><strong aria-hidden="true">1.2.</strong> 墙推 VSCode!</a></li><li class="chapter-item "><a href="../first-try/cargo.html"><strong aria-hidden="true">1.3.</strong> 认识 Cargo</a></li><li class="chapter-item "><a href="../first-try/hello-world.html"><strong aria-hidden="true">1.4.</strong> 不仅仅是 Hello world</a></li><li class="chapter-item "><a href="../first-try/slowly-downloading.html"><strong aria-hidden="true">1.5.</strong> 下载依赖太慢了？</a></li></ol></li><li class="chapter-item "><a href="../basic/intro.html"><strong aria-hidden="true">2.</strong> Rust 基础入门</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/variable.html"><strong aria-hidden="true">2.1.</strong> 变量绑定与解构</a></li><li class="chapter-item "><a href="../basic/base-type/index.html"><strong aria-hidden="true">2.2.</strong> 基本类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/base-type/numbers.html"><strong aria-hidden="true">2.2.1.</strong> 数值类型</a></li><li class="chapter-item "><a href="../basic/base-type/char-bool.html"><strong aria-hidden="true">2.2.2.</strong> 字符、布尔、单元类型</a></li><li class="chapter-item "><a href="../basic/base-type/statement-expression.html"><strong aria-hidden="true">2.2.3.</strong> 语句与表达式</a></li><li class="chapter-item "><a href="../basic/base-type/function.html"><strong aria-hidden="true">2.2.4.</strong> 函数</a></li></ol></li><li class="chapter-item "><a href="../basic/ownership/index.html"><strong aria-hidden="true">2.3.</strong> 所有权和借用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/ownership/ownership.html"><strong aria-hidden="true">2.3.1.</strong> 所有权</a></li><li class="chapter-item "><a href="../basic/ownership/borrowing.html"><strong aria-hidden="true">2.3.2.</strong> 引用与借用</a></li></ol></li><li class="chapter-item "><a href="../basic/compound-type/intro.html"><strong aria-hidden="true">2.4.</strong> 复合类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/compound-type/string-slice.html"><strong aria-hidden="true">2.4.1.</strong> 字符串与切片</a></li><li class="chapter-item "><a href="../basic/compound-type/tuple.html"><strong aria-hidden="true">2.4.2.</strong> 元组</a></li><li class="chapter-item "><a href="../basic/compound-type/struct.html"><strong aria-hidden="true">2.4.3.</strong> 结构体</a></li><li class="chapter-item "><a href="../basic/compound-type/enum.html"><strong aria-hidden="true">2.4.4.</strong> 枚举</a></li><li class="chapter-item "><a href="../basic/compound-type/array.html"><strong aria-hidden="true">2.4.5.</strong> 数组</a></li></ol></li><li class="chapter-item "><a href="../basic/flow-control.html"><strong aria-hidden="true">2.5.</strong> 流程控制</a></li><li class="chapter-item "><a href="../basic/match-pattern/intro.html"><strong aria-hidden="true">2.6.</strong> 模式匹配</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/match-pattern/match-if-let.html"><strong aria-hidden="true">2.6.1.</strong> match 和 if let</a></li><li class="chapter-item "><a href="../basic/match-pattern/option.html"><strong aria-hidden="true">2.6.2.</strong> 解构 Option</a></li><li class="chapter-item "><a href="../basic/match-pattern/pattern-match.html"><strong aria-hidden="true">2.6.3.</strong> 模式适用场景</a></li><li class="chapter-item "><a href="../basic/match-pattern/all-patterns.html"><strong aria-hidden="true">2.6.4.</strong> 全模式列表</a></li></ol></li><li class="chapter-item "><a href="../basic/method.html"><strong aria-hidden="true">2.7.</strong> 方法 Method</a></li><li class="chapter-item "><a href="../basic/trait/intro.html"><strong aria-hidden="true">2.8.</strong> 泛型和特征</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/trait/generic.html"><strong aria-hidden="true">2.8.1.</strong> 泛型 Generics</a></li><li class="chapter-item "><a href="../basic/trait/trait.html"><strong aria-hidden="true">2.8.2.</strong> 特征 Trait</a></li><li class="chapter-item "><a href="../basic/trait/trait-object.html"><strong aria-hidden="true">2.8.3.</strong> 特征对象</a></li><li class="chapter-item "><a href="../basic/trait/advance-trait.html"><strong aria-hidden="true">2.8.4.</strong> 进一步深入特征</a></li></ol></li><li class="chapter-item "><a href="../basic/collections/intro.html"><strong aria-hidden="true">2.9.</strong> 集合类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/collections/vector.html"><strong aria-hidden="true">2.9.1.</strong> 动态数组 Vector</a></li><li class="chapter-item "><a href="../basic/collections/hashmap.html"><strong aria-hidden="true">2.9.2.</strong> KV 存储 HashMap</a></li></ol></li><li class="chapter-item "><a 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class="chapter-item "><a href="../basic/crate-module/use.html"><strong aria-hidden="true">2.12.3.</strong> 使用 use 引入模块及受限可见性</a></li></ol></li><li class="chapter-item "><a href="../basic/comment.html"><strong aria-hidden="true">2.13.</strong> 注释和文档</a></li><li class="chapter-item "><a href="../basic/formatted-output.html"><strong aria-hidden="true">2.14.</strong> 格式化输出</a></li></ol></li><li class="chapter-item "><a href="../basic-practice/intro.html"><strong aria-hidden="true">3.</strong> 入门实战：文件搜索工具</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic-practice/base-features.html"><strong aria-hidden="true">3.1.</strong> 基本功能</a></li><li class="chapter-item "><a href="../basic-practice/refactoring.html"><strong aria-hidden="true">3.2.</strong> 增加模块化和错误处理</a></li><li class="chapter-item "><a href="../basic-practice/tests.html"><strong aria-hidden="true">3.3.</strong> 测试驱动开发</a></li><li class="chapter-item "><a href="../basic-practice/envs.html"><strong aria-hidden="true">3.4.</strong> 使用环境变量</a></li><li class="chapter-item "><a href="../basic-practice/stderr.html"><strong aria-hidden="true">3.5.</strong> 重定向错误信息的输出</a></li><li class="chapter-item "><a href="../basic-practice/iterators.html"><strong aria-hidden="true">3.6.</strong> 使用迭代器来改进程序(可选)</a></li></ol></li><li class="chapter-item "><li class="part-title">Rust 语言进阶学习</li><li class="spacer"></li><li class="chapter-item "><a href="../advance/intro.html"><strong aria-hidden="true">4.</strong> Rust 高级进阶</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/lifetime/intro.html"><strong aria-hidden="true">4.1.</strong> 生命周期</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/lifetime/advance.html"><strong aria-hidden="true">4.1.1.</strong> 深入生命周期</a></li><li class="chapter-item "><a href="../advance/lifetime/static.html"><strong aria-hidden="true">4.1.2.</strong> &'static 和 T: 'static</a></li></ol></li><li class="chapter-item "><a href="../advance/functional-programing/intro.html"><strong aria-hidden="true">4.2.</strong> 函数式编程: 闭包、迭代器</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/functional-programing/closure.html"><strong aria-hidden="true">4.2.1.</strong> 闭包 Closure</a></li><li class="chapter-item "><a href="../advance/functional-programing/iterator.html"><strong aria-hidden="true">4.2.2.</strong> 迭代器 Iterator</a></li></ol></li><li class="chapter-item "><a href="../advance/into-types/intro.html"><strong aria-hidden="true">4.3.</strong> 深入类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/into-types/converse.html"><strong aria-hidden="true">4.3.1.</strong> 类型转换</a></li><li class="chapter-item "><a href="../advance/into-types/custom-type.html"><strong aria-hidden="true">4.3.2.</strong> newtype 和 类型别名</a></li><li class="chapter-item "><a href="../advance/into-types/sized.html"><strong aria-hidden="true">4.3.3.</strong> Sized 和不定长类型 DST</a></li><li class="chapter-item "><a href="../advance/into-types/enum-int.html"><strong aria-hidden="true">4.3.4.</strong> 枚举和整数</a></li></ol></li><li class="chapter-item "><a href="../advance/smart-pointer/intro.html"><strong aria-hidden="true">4.4.</strong> 智能指针</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/smart-pointer/box.html"><strong aria-hidden="true">4.4.1.</strong> Box堆对象分配</a></li><li class="chapter-item "><a href="../advance/smart-pointer/deref.html"><strong aria-hidden="true">4.4.2.</strong> Deref 解引用</a></li><li class="chapter-item "><a href="../advance/smart-pointer/drop.html"><strong aria-hidden="true">4.4.3.</strong> Drop 释放资源</a></li><li class="chapter-item "><a href="../advance/smart-pointer/rc-arc.html"><strong aria-hidden="true">4.4.4.</strong> Rc 与 Arc 实现 1vN 所有权机制</a></li><li class="chapter-item "><a href="../advance/smart-pointer/cell-refcell.html"><strong aria-hidden="true">4.4.5.</strong> Cell 与 RefCell 内部可变性</a></li></ol></li><li class="chapter-item "><a href="../advance/circle-self-ref/intro.html"><strong aria-hidden="true">4.5.</strong> 循环引用与自引用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/circle-self-ref/circle-reference.html"><strong aria-hidden="true">4.5.1.</strong> Weak 与循环引用</a></li><li class="chapter-item "><a href="../advance/circle-self-ref/self-referential.html"><strong aria-hidden="true">4.5.2.</strong> 结构体中的自引用</a></li></ol></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/intro.html"><strong aria-hidden="true">4.6.</strong> 多线程并发编程</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/concurrency-with-threads/concurrency-parallelism.html"><strong aria-hidden="true">4.6.1.</strong> 并发和并行</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/thread.html"><strong aria-hidden="true">4.6.2.</strong> 使用多线程</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/message-passing.html"><strong aria-hidden="true">4.6.3.</strong> 线程同步：消息传递</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/sync1.html"><strong aria-hidden="true">4.6.4.</strong> 线程同步：锁、Condvar 和信号量</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/sync2.html"><strong aria-hidden="true">4.6.5.</strong> 线程同步：Atomic 原子操作与内存顺序</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/send-sync.html"><strong aria-hidden="true">4.6.6.</strong> 基于 Send 和 Sync 的线程安全</a></li></ol></li><li class="chapter-item "><a href="../advance/global-variable.html"><strong aria-hidden="true">4.7.</strong> 全局变量</a></li><li class="chapter-item "><a href="../advance/errors.html"><strong aria-hidden="true">4.8.</strong> 错误处理</a></li><li class="chapter-item "><a href="../advance/unsafe/intro.html"><strong aria-hidden="true">4.9.</strong> Unsafe Rust</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/unsafe/superpowers.html"><strong aria-hidden="true">4.9.1.</strong> 五种兵器</a></li><li class="chapter-item "><a href="../advance/unsafe/inline-asm.html"><strong aria-hidden="true">4.9.2.</strong> 内联汇编</a></li></ol></li><li class="chapter-item "><a href="../advance/macro.html"><strong aria-hidden="true">4.10.</strong> Macro 宏编程</a></li><li class="chapter-item "><a href="../advance/async/intro.html"><strong aria-hidden="true">4.11.</strong> async/await 异步编程</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/async/getting-started.html"><strong aria-hidden="true">4.11.1.</strong> async 编程入门</a></li><li class="chapter-item "><a href="../advance/async/future-excuting.html"><strong aria-hidden="true">4.11.2.</strong> 底层探秘: Future 执行与任务调度</a></li><li class="chapter-item "><a href="../advance/async/pin-unpin.html"><strong aria-hidden="true">4.11.3.</strong> 定海神针 Pin 和 Unpin</a></li><li class="chapter-item "><a href="../advance/async/async-await.html"><strong aria-hidden="true">4.11.4.</strong> async/await 和 Stream 流处理</a></li><li class="chapter-item "><a href="../advance/async/multi-futures-simultaneous.html"><strong aria-hidden="true">4.11.5.</strong> 同时运行多个 Future</a></li><li class="chapter-item "><a href="../advance/async/pain-points-and-workarounds.html"><strong aria-hidden="true">4.11.6.</strong> 一些疑难问题的解决办法</a></li><li class="chapter-item "><a href="../advance/async/web-server.html"><strong aria-hidden="true">4.11.7.</strong> 实践应用：Async Web 服务器</a></li></ol></li></ol></li><li class="chapter-item "><a href="../advance-practice1/intro.html"><strong aria-hidden="true">5.</strong> 进阶实战1: 实现一个 web 服务器</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance-practice1/web-server.html"><strong aria-hidden="true">5.1.</strong> 单线程版本</a></li><li class="chapter-item "><a href="../advance-practice1/multi-threads.html"><strong aria-hidden="true">5.2.</strong> 多线程版本</a></li><li class="chapter-item "><a href="../advance-practice1/graceful-shutdown.html"><strong aria-hidden="true">5.3.</strong> 优雅关闭和资源清理</a></li></ol></li><li class="chapter-item "><a href="../advance-practice/intro.html"><strong aria-hidden="true">6.</strong> 进阶实战2: 实现一个简单 Redis</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance-practice/overview.html"><strong aria-hidden="true">6.1.</strong> tokio 概览</a></li><li class="chapter-item "><a href="../advance-practice/getting-startted.html"><strong aria-hidden="true">6.2.</strong> 使用初印象</a></li><li class="chapter-item "><a href="../advance-practice/spawning.html"><strong aria-hidden="true">6.3.</strong> 创建异步任务</a></li><li class="chapter-item "><a href="../advance-practice/shared-state.html"><strong aria-hidden="true">6.4.</strong> 共享状态</a></li><li class="chapter-item "><a href="../advance-practice/channels.html"><strong aria-hidden="true">6.5.</strong> 消息传递</a></li><li class="chapter-item "><a href="../advance-practice/io.html"><strong aria-hidden="true">6.6.</strong> I/O</a></li><li class="chapter-item "><a href="../advance-practice/frame.html"><strong aria-hidden="true">6.7.</strong> 解析数据帧</a></li><li class="chapter-item "><a href="../advance-practice/async.html"><strong aria-hidden="true">6.8.</strong> 深入 async</a></li><li class="chapter-item "><a href="../advance-practice/select.html"><strong aria-hidden="true">6.9.</strong> select</a></li><li class="chapter-item "><a href="../advance-practice/stream.html"><strong aria-hidden="true">6.10.</strong> 类似迭代器的 Stream</a></li><li class="chapter-item "><a href="../advance-practice/graceful-shutdown.html"><strong aria-hidden="true">6.11.</strong> 优雅的关闭</a></li><li class="chapter-item "><a href="../advance-practice/bridging-with-sync.html"><strong aria-hidden="true">6.12.</strong> 异步跟同步共存</a></li></ol></li><li class="chapter-item "><a href="../difficulties/intro.html"><strong aria-hidden="true">7.</strong> Rust 难点攻关</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../difficulties/slice.html"><strong aria-hidden="true">7.1.</strong> 切片和切片引用</a></li><li class="chapter-item "><a href="../difficulties/eq.html"><strong aria-hidden="true">7.2.</strong> Eq 和 PartialEq</a></li><li class="chapter-item "><a href="../difficulties/string.html"><strong aria-hidden="true">7.3.</strong> String、&str 和 str TODO</a></li><li class="chapter-item "><a href="../difficulties/lifetime.html"><strong aria-hidden="true">7.4.</strong> 作用域、生命周期和 NLL TODO</a></li><li class="chapter-item "><a href="../difficulties/move-copy.html"><strong aria-hidden="true">7.5.</strong> move、Copy 和 Clone TODO</a></li><li class="chapter-item "><a href="../advance/difficulties/pointer.html"><strong aria-hidden="true">7.6.</strong> 裸指针、引用和智能指针 TODO</a></li></ol></li><li class="chapter-item "><li class="part-title">常用工具链</li><li class="spacer"></li><li class="chapter-item "><a href="../test/intro.html"><strong aria-hidden="true">8.</strong> 自动化测试</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../test/write-tests.html"><strong aria-hidden="true">8.1.</strong> 编写测试及控制执行</a></li><li class="chapter-item "><a href="../test/unit-integration-test.html"><strong aria-hidden="true">8.2.</strong> 单元测试和集成测试</a></li><li class="chapter-item "><a href="../test/assertion.html"><strong aria-hidden="true">8.3.</strong> 断言 assertion</a></li><li class="chapter-item "><a href="../test/ci.html"><strong aria-hidden="true">8.4.</strong> 用 GitHub Actions 进行持续集成</a></li><li class="chapter-item "><a href="../test/benchmark.html"><strong aria-hidden="true">8.5.</strong> 基准测试 benchmark</a></li></ol></li><li class="chapter-item "><a href="../cargo/intro.html"><strong aria-hidden="true">9.</strong> Cargo 使用指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/getting-started.html"><strong aria-hidden="true">9.1.</strong> 上手使用</a></li><li class="chapter-item "><a href="../cargo/guide/intro.html"><strong aria-hidden="true">9.2.</strong> 基础指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/guide/why-exist.html"><strong aria-hidden="true">9.2.1.</strong> 为何会有 Cargo</a></li><li class="chapter-item "><a href="../cargo/guide/download-package.html"><strong aria-hidden="true">9.2.2.</strong> 下载并构建 Package</a></li><li class="chapter-item "><a href="../cargo/guide/dependencies.html"><strong aria-hidden="true">9.2.3.</strong> 添加依赖</a></li><li class="chapter-item "><a href="../cargo/guide/package-layout.html"><strong aria-hidden="true">9.2.4.</strong> Package 目录结构</a></li><li class="chapter-item "><a href="../cargo/guide/cargo-toml-lock.html"><strong aria-hidden="true">9.2.5.</strong> Cargo.toml vs Cargo.lock</a></li><li class="chapter-item "><a href="../cargo/guide/tests-ci.html"><strong aria-hidden="true">9.2.6.</strong> 测试和 CI</a></li><li class="chapter-item "><a href="../cargo/guide/cargo-cache.html"><strong aria-hidden="true">9.2.7.</strong> Cargo 缓存</a></li><li class="chapter-item "><a href="../cargo/guide/build-cache.html"><strong aria-hidden="true">9.2.8.</strong> Build 缓存</a></li></ol></li><li class="chapter-item "><a href="../cargo/reference/intro.html"><strong aria-hidden="true">9.3.</strong> 进阶指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/specify-deps.html"><strong aria-hidden="true">9.3.1.</strong> 指定依赖项</a></li><li class="chapter-item "><a href="../cargo/reference/deps-overriding.html"><strong aria-hidden="true">9.3.2.</strong> 依赖覆盖</a></li><li class="chapter-item "><a href="../cargo/reference/manifest.html"><strong aria-hidden="true">9.3.3.</strong> Cargo.toml 清单详解</a></li><li class="chapter-item "><a href="../cargo/reference/cargo-target.html"><strong aria-hidden="true">9.3.4.</strong> Cargo Target</a></li><li class="chapter-item "><a href="../cargo/reference/workspaces.html"><strong aria-hidden="true">9.3.5.</strong> 工作空间 Workspace</a></li><li class="chapter-item "><a href="../cargo/reference/features/intro.html"><strong aria-hidden="true">9.3.6.</strong> 条件编译 Features</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/features/examples.html"><strong aria-hidden="true">9.3.6.1.</strong> Features 示例</a></li></ol></li><li class="chapter-item "><a href="../cargo/reference/profiles.html"><strong aria-hidden="true">9.3.7.</strong> 发布配置 Profile</a></li><li class="chapter-item "><a href="../cargo/reference/configuration.html"><strong aria-hidden="true">9.3.8.</strong> 通过 config.toml 对 Cargo 进行配置</a></li><li class="chapter-item "><a href="../cargo/reference/publishing-on-crates.io.html"><strong aria-hidden="true">9.3.9.</strong> 发布到 crates.io</a></li><li class="chapter-item "><a href="../cargo/reference/build-script/intro.html"><strong aria-hidden="true">9.3.10.</strong> 构建脚本 build.rs</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/build-script/examples.html"><strong aria-hidden="true">9.3.10.1.</strong> 构建脚本示例</a></li></ol></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">开发实践</li><li class="spacer"></li><li class="chapter-item "><a href="../usecases/intro.html"><strong aria-hidden="true">10.</strong> 企业落地实践</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usecases/aws-rust.html"><strong aria-hidden="true">10.1.</strong> AWS 为何这么喜欢 Rust?</a></li></ol></li><li class="chapter-item expanded "><a href="../logs/intro.html"><strong aria-hidden="true">11.</strong> 日志和监控</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../logs/about-log.html"><strong aria-hidden="true">11.1.</strong> 日志详解</a></li><li class="chapter-item "><a href="../logs/log.html"><strong aria-hidden="true">11.2.</strong> 日志门面 log</a></li><li class="chapter-item "><a href="../logs/tracing.html"><strong aria-hidden="true">11.3.</strong> 使用 tracing 记录日志</a></li><li class="chapter-item expanded "><a href="../logs/tracing-logger.html" class="active"><strong aria-hidden="true">11.4.</strong> 自定义 tracing 的输出格式</a></li><li class="chapter-item "><a href="../logs/observe/intro.html"><strong aria-hidden="true">11.5.</strong> 监控</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../logs/observe/about-observe.html"><strong aria-hidden="true">11.5.1.</strong> 可观测性</a></li><li class="chapter-item "><a href="../logs/observe/trace.html"><strong aria-hidden="true">11.5.2.</strong> 分布式追踪</a></li></ol></li></ol></li><li class="chapter-item "><a href="../practice/intro.html"><strong aria-hidden="true">12.</strong> Rust 最佳实践</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../practice/third-party-libs.html"><strong aria-hidden="true">12.1.</strong> 日常开发三方库精选</a></li><li class="chapter-item "><a href="../practice/naming.html"><strong aria-hidden="true">12.2.</strong> 命名规范</a></li><li class="chapter-item "><a href="../practice/interview.html"><strong aria-hidden="true">12.3.</strong> 面试经验</a></li><li class="chapter-item "><a href="../practice/best-pratice.html"><strong aria-hidden="true">12.4.</strong> 代码开发实践 todo</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/intro.html"><strong aria-hidden="true">13.</strong> 手把手带你实现链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/do-we-need-it.html"><strong aria-hidden="true">13.1.</strong> 我们到底需不需要链表</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/intro.html"><strong aria-hidden="true">13.2.</strong> 不太优秀的单向链表：栈</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/bad-stack/layout.html"><strong aria-hidden="true">13.2.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/basic-operations.html"><strong aria-hidden="true">13.2.2.</strong> 基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/final-code.html"><strong aria-hidden="true">13.2.3.</strong> 最后实现</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/intro.html"><strong aria-hidden="true">13.3.</strong> 还可以的单向链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/ok-stack/type-optimizing.html"><strong aria-hidden="true">13.3.1.</strong> 优化类型定义</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/peek.html"><strong aria-hidden="true">13.3.2.</strong> 定义 Peek 函数</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/iter.html"><strong aria-hidden="true">13.3.3.</strong> IntoIter 和 Iter</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/itermut.html"><strong aria-hidden="true">13.3.4.</strong> IterMut 以及完整代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/persistent-stack/intro.html"><strong aria-hidden="true">13.4.</strong> 持久化单向链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/persistent-stack/layout.html"><strong aria-hidden="true">13.4.1.</strong> 数据布局和基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/persistent-stack/drop-arc.html"><strong aria-hidden="true">13.4.2.</strong> Drop、Arc 及完整代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/deque/intro.html"><strong aria-hidden="true">13.5.</strong> 不咋样的双端队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/deque/layout.html"><strong aria-hidden="true">13.5.1.</strong> 数据布局和基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/deque/peek.html"><strong aria-hidden="true">13.5.2.</strong> Peek</a></li><li class="chapter-item "><a href="../too-many-lists/deque/symmetric.html"><strong aria-hidden="true">13.5.3.</strong> 基本操作的对称镜像</a></li><li class="chapter-item "><a href="../too-many-lists/deque/iterator.html"><strong aria-hidden="true">13.5.4.</strong> 迭代器</a></li><li class="chapter-item "><a href="../too-many-lists/deque/final-code.html"><strong aria-hidden="true">13.5.5.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/intro.html"><strong aria-hidden="true">13.6.</strong> 不错的 unsafe 队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/layout.html"><strong aria-hidden="true">13.6.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/basics.html"><strong aria-hidden="true">13.6.2.</strong> 基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/miri.html"><strong aria-hidden="true">13.6.3.</strong> Miri</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/stacked-borrow.html"><strong aria-hidden="true">13.6.4.</strong> 栈借用</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/testing-stacked-borrow.html"><strong aria-hidden="true">13.6.5.</strong> 测试栈借用</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/layout2.html"><strong aria-hidden="true">13.6.6.</strong> 数据布局 2</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/extra-junk.html"><strong aria-hidden="true">13.6.7.</strong> 额外的操作</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/final-code.html"><strong aria-hidden="true">13.6.8.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/intro.html"><strong aria-hidden="true">13.7.</strong> 生产级的双向 unsafe 队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/layout.html"><strong aria-hidden="true">13.7.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/variance-and-phantomData.html"><strong aria-hidden="true">13.7.2.</strong> 型变与子类型</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/basics.html"><strong aria-hidden="true">13.7.3.</strong> 基础结构</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/drop-and-panic-safety.html"><strong aria-hidden="true">13.7.4.</strong> 恐慌与安全</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/boring-combinatorics.html"><strong aria-hidden="true">13.7.5.</strong> 无聊的组合</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/filling-in-random-bits.html"><strong aria-hidden="true">13.7.6.</strong> 其它特征</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/testing.html"><strong aria-hidden="true">13.7.7.</strong> 测试</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/send-sync-and-compile-tests.html"><strong aria-hidden="true">13.7.8.</strong> Send,Sync和编译测试</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/implementing-cursors.html"><strong aria-hidden="true">13.7.9.</strong> 实现游标</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/testing-cursors.html"><strong aria-hidden="true">13.7.10.</strong> 测试游标</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/final-code.html"><strong aria-hidden="true">13.7.11.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/advanced-lists/intro.html"><strong aria-hidden="true">13.8.</strong> 使用高级技巧实现链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/advanced-lists/double-singly.html"><strong aria-hidden="true">13.8.1.</strong> 双单向链表</a></li><li class="chapter-item "><a href="../too-many-lists/advanced-lists/stack-allocated.html"><strong aria-hidden="true">13.8.2.</strong> 栈上的链表</a></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">攻克编译错误</li><li class="spacer"></li><li class="chapter-item "><a href="../compiler/intro.html"><strong aria-hidden="true">14.</strong> 征服编译错误</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/intro.html"><strong aria-hidden="true">14.1.</strong> 对抗编译检查</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/intro.html"><strong aria-hidden="true">14.1.1.</strong> 生命周期</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/too-long1.html"><strong aria-hidden="true">14.1.1.1.</strong> 生命周期过大-01</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/too-long2.html"><strong aria-hidden="true">14.1.1.2.</strong> 生命周期过大-02</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/loop.html"><strong aria-hidden="true">14.1.1.3.</strong> 循环中的生命周期</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/closure-with-static.html"><strong aria-hidden="true">14.1.1.4.</strong> 闭包碰到特征对象-01</a></li></ol></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/intro.html"><strong aria-hidden="true">14.1.2.</strong> 重复借用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/ref-exist-in-out-fn.html"><strong aria-hidden="true">14.1.2.1.</strong> 同时在函数内外使用引用</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/borrow-distinct-fields-of-struct.html"><strong aria-hidden="true">14.1.2.2.</strong> 智能指针引起的重复借用错误</a></li></ol></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/unconstrained.html"><strong aria-hidden="true">14.1.3.</strong> 类型未限制(todo)</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/phantom-data.html"><strong aria-hidden="true">14.1.4.</strong> 幽灵数据(todo)</a></li></ol></li><li class="chapter-item "><a href="../compiler/pitfalls/index.html"><strong aria-hidden="true">14.2.</strong> Rust 常见陷阱</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/pitfalls/use-vec-in-for.html"><strong aria-hidden="true">14.2.1.</strong> for 循环中使用外部数组</a></li><li class="chapter-item "><a href="../compiler/pitfalls/stack-overflow.html"><strong aria-hidden="true">14.2.2.</strong> 线程类型导致的栈溢出</a></li><li class="chapter-item "><a href="../compiler/pitfalls/arithmetic-overflow.html"><strong aria-hidden="true">14.2.3.</strong> 算术溢出导致的 panic</a></li><li class="chapter-item "><a href="../compiler/pitfalls/closure-with-lifetime.html"><strong aria-hidden="true">14.2.4.</strong> 闭包中奇怪的生命周期</a></li><li class="chapter-item "><a href="../compiler/pitfalls/the-disabled-mutability.html"><strong aria-hidden="true">14.2.5.</strong> 可变变量不可变？</a></li><li class="chapter-item "><a href="../compiler/pitfalls/multiple-mutable-references.html"><strong aria-hidden="true">14.2.6.</strong> 可变借用失败引发的深入思考</a></li><li class="chapter-item "><a href="../compiler/pitfalls/lazy-iterators.html"><strong aria-hidden="true">14.2.7.</strong> 不太勤快的迭代器</a></li><li class="chapter-item "><a href="../compiler/pitfalls/weird-ranges.html"><strong aria-hidden="true">14.2.8.</strong> 奇怪的序列 x..y</a></li><li class="chapter-item "><a href="../compiler/pitfalls/iterator-everywhere.html"><strong aria-hidden="true">14.2.9.</strong> 无处不在的迭代器</a></li><li class="chapter-item "><a href="../compiler/pitfalls/main-with-channel-blocked.html"><strong aria-hidden="true">14.2.10.</strong> 线程间传递消息导致主线程无法结束</a></li><li class="chapter-item "><a href="../compiler/pitfalls/utf8-performance.html"><strong aria-hidden="true">14.2.11.</strong> 警惕 UTF-8 引发的性能隐患</a></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">性能优化</li><li class="spacer"></li><li class="chapter-item "><a href="../profiling/intro.html"><strong aria-hidden="true">15.</strong> Rust 性能优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/memory/intro.html"><strong aria-hidden="true">15.1.</strong> 深入内存 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/memory/pointer-ref.html"><strong aria-hidden="true">15.1.1.</strong> 指针和引用 todo</a></li><li class="chapter-item "><a href="../profiling/memory/uninit.html"><strong aria-hidden="true">15.1.2.</strong> 未初始化内存 todo</a></li><li class="chapter-item "><a href="../profiling/memory/allocation.html"><strong aria-hidden="true">15.1.3.</strong> 内存分配 todo</a></li><li class="chapter-item "><a href="../profiling/memory/layout.html"><strong aria-hidden="true">15.1.4.</strong> 内存布局 todo</a></li><li class="chapter-item "><a href="../profiling/memory/virtual.html"><strong aria-hidden="true">15.1.5.</strong> 虚拟内存 todo</a></li></ol></li><li class="chapter-item "><a href="../profiling/performance/intro.html"><strong aria-hidden="true">15.2.</strong> 性能调优 doing</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/performance/string.html"><strong aria-hidden="true">15.2.1.</strong> 字符串操作性能</a></li><li class="chapter-item "><a href="../profiling/performance/deep-into-move.html"><strong aria-hidden="true">15.2.2.</strong> 深入理解 move</a></li><li class="chapter-item "><a href="../profiling/performance/early-optimise.html"><strong aria-hidden="true">15.2.3.</strong> 糟糕的提前优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/clone-copy.html"><strong aria-hidden="true">15.2.4.</strong> Clone 和 Copy todo</a></li><li class="chapter-item "><a href="../profiling/performance/runtime-check.html"><strong aria-hidden="true">15.2.5.</strong> 减少 Runtime check(todo)</a></li><li class="chapter-item "><a href="../profiling/performance/cpu-cache.html"><strong aria-hidden="true">15.2.6.</strong> CPU 缓存性能优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/calculate.html"><strong aria-hidden="true">15.2.7.</strong> 计算性能优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/heap-stack.html"><strong aria-hidden="true">15.2.8.</strong> 堆和栈 todo</a></li><li class="chapter-item "><a href="../profiling/performance/allocator.html"><strong aria-hidden="true">15.2.9.</strong> 内存 allocator todo</a></li><li class="chapter-item "><a href="../profiling/performance/tools.html"><strong aria-hidden="true">15.2.10.</strong> 常用性能测试工具 todo</a></li><li class="chapter-item "><a href="../profiling/performance/enum.html"><strong aria-hidden="true">15.2.11.</strong> Enum 内存优化 todo</a></li></ol></li><li class="chapter-item "><a href="../profiling/compiler/intro.html"><strong aria-hidden="true">15.3.</strong> 编译优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/compiler/llvm.html"><strong aria-hidden="true">15.3.1.</strong> LLVM todo</a></li><li class="chapter-item "><a href="../profiling/compiler/attributes.html"><strong aria-hidden="true">15.3.2.</strong> 常见属性标记 todo</a></li><li class="chapter-item "><a href="../profiling/compiler/speed-up.html"><strong aria-hidden="true">15.3.3.</strong> 提升编译速度 todo</a></li><li class="chapter-item "><a href="../profiling/compiler/optimization/intro.html"><strong aria-hidden="true">15.3.4.</strong> 编译器优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/compiler/optimization/option.html"><strong aria-hidden="true">15.3.4.1.</strong> Option 枚举 todo</a></li></ol></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">附录</li><li class="spacer"></li><li class="chapter-item "><div><strong aria-hidden="true">16.</strong> Appendix</div><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../appendix/keywords.html"><strong aria-hidden="true">16.1.</strong> 关键字</a></li><li class="chapter-item "><a href="../appendix/operators.html"><strong aria-hidden="true">16.2.</strong> 运算符与符号</a></li><li class="chapter-item "><a href="../appendix/expressions.html"><strong aria-hidden="true">16.3.</strong> 表达式</a></li><li class="chapter-item "><a href="../appendix/derive.html"><strong aria-hidden="true">16.4.</strong> 派生特征 trait</a></li><li class="chapter-item "><a href="../appendix/prelude.html"><strong aria-hidden="true">16.5.</strong> prelude 模块 todo</a></li><li class="chapter-item "><a href="../appendix/rust-version.html"><strong aria-hidden="true">16.6.</strong> Rust 版本说明</a></li><li class="chapter-item "><a href="../appendix/rust-versions/intro.html"><strong aria-hidden="true">16.7.</strong> Rust 历次版本更新解读</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../appendix/rust-versions/1.58.html"><strong aria-hidden="true">16.7.1.</strong> 1.58</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.59.html"><strong aria-hidden="true">16.7.2.</strong> 1.59</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.60.html"><strong aria-hidden="true">16.7.3.</strong> 1.60</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.61.html"><strong aria-hidden="true">16.7.4.</strong> 1.61</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.62.html"><strong aria-hidden="true">16.7.5.</strong> 1.62</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.63.html"><strong aria-hidden="true">16.7.6.</strong> 1.63</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.64.html"><strong aria-hidden="true">16.7.7.</strong> 1.64</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.65.html"><strong aria-hidden="true">16.7.8.</strong> 1.65</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.66.html"><strong aria-hidden="true">16.7.9.</strong> 1.66</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.67.html"><strong aria-hidden="true">16.7.10.</strong> 1.67</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.68.html"><strong aria-hidden="true">16.7.11.</strong> 1.68</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.69.html"><strong aria-hidden="true">16.7.12.</strong> 1.69</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.70.html"><strong aria-hidden="true">16.7.13.</strong> 1.70</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.71.html"><strong aria-hidden="true">16.7.14.</strong> 1.71</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.72.html"><strong aria-hidden="true">16.7.15.</strong> 1.72</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.73.html"><strong aria-hidden="true">16.7.16.</strong> 1.73</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.74.html"><strong aria-hidden="true">16.7.17.</strong> 1.74</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.75.html"><strong aria-hidden="true">16.7.18.</strong> 1.75</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.76.html"><strong aria-hidden="true">16.7.19.</strong> 1.76</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.77.html"><strong aria-hidden="true">16.7.20.</strong> 1.77</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.78.html"><strong aria-hidden="true">16.7.21.</strong> 1.78</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.79.html"><strong aria-hidden="true">16.7.22.</strong> 1.79</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.80.html"><strong aria-hidden="true">16.7.23.</strong> 1.80</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.81.html"><strong aria-hidden="true">16.7.24.</strong> 1.81</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.82.html"><strong aria-hidden="true">16.7.25.</strong> 1.82</a></li></ol></li></ol></li></ol>
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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>
<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>
<blockquote>
<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>
</blockquote>
<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>
<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>
<h2 id="打地基1"><a class="header" href="#打地基1">打地基(1)</a></h2>
<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>
<p>然后引入以下依赖：</p>
<pre><code class="language-toml"># in cargo.toml
[dependencies]
serde_json = &quot;1&quot;
tracing = &quot;0.1&quot;
tracing-subscriber = &quot;0.3&quot;
</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><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 = &quot;first example&quot;);
}</code></pre></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><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&lt;S&gt; Layer&lt;S&gt; for CustomLayer where S: tracing::Subscriber {}
<span class="boring">}</span></code></pre></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><pre class="playground"><code class="language-rust editable edition2021">// in examples/figure_0/custom_layer.rs
where
S: tracing::Subscriber,
{
fn on_event(
&amp;self,
event: &amp;tracing::Event&lt;'_&gt;,
_ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
println!(&quot;Got event!&quot;);
println!(&quot; level={:?}&quot;, event.metadata().level());
println!(&quot; target={:?}&quot;, event.metadata().target());
println!(&quot; name={:?}&quot;, event.metadata().name());
for field in event.fields() {
println!(&quot; field={}&quot;, field.name());
}
}
}</code></pre></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=&quot;figure_1&quot;
name=&quot;event examples/figure_1/main.rs:10&quot;
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><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(&amp;mut self, field: &amp;tracing::field::Field, value: f64) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_i64(&amp;mut self, field: &amp;tracing::field::Field, value: i64) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_u64(&amp;mut self, field: &amp;tracing::field::Field, value: u64) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_bool(&amp;mut self, field: &amp;tracing::field::Field, value: bool) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_str(&amp;mut self, field: &amp;tracing::field::Field, value: &amp;str) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_error(
&amp;mut self,
field: &amp;tracing::field::Field,
value: &amp;(dyn std::error::Error + 'static),
) {
println!(&quot; field={} value={}&quot;, field.name(), value)
}
fn record_debug(&amp;mut self, field: &amp;tracing::field::Field, value: &amp;dyn std::fmt::Debug) {
println!(&quot; field={} value={:?}&quot;, field.name(), value)
}
}
<span class="boring">}</span></code></pre></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(&amp;mut visitor)</code> 可以访问其中的所有值。</p>
<pre><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(
&amp;self,
event: &amp;tracing::Event&lt;'_&gt;,
_ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
println!(&quot;Got event!&quot;);
println!(&quot; level={:?}&quot;, event.metadata().level());
println!(&quot; target={:?}&quot;, event.metadata().target());
println!(&quot; name={:?}&quot;, event.metadata().name());
let mut visitor = PrintlnVisitor;
event.record(&amp;mut visitor);
}
<span class="boring">}</span></code></pre></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=&quot;figure_2&quot;
name=&quot;event examples/figure_2/main.rs:10&quot;
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><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&lt;'a&gt; tracing::field::Visit for JsonVisitor&lt;'a&gt; {
fn record_f64(&amp;mut self, field: &amp;tracing::field::Field, value: f64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_i64(&amp;mut self, field: &amp;tracing::field::Field, value: i64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_u64(&amp;mut self, field: &amp;tracing::field::Field, value: u64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_bool(&amp;mut self, field: &amp;tracing::field::Field, value: bool) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_str(&amp;mut self, field: &amp;tracing::field::Field, value: &amp;str) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_error(
&amp;mut self,
field: &amp;tracing::field::Field,
value: &amp;(dyn std::error::Error + 'static),
) {
self.0.insert(
field.name().to_string(),
serde_json::json!(value.to_string()),
);
}
fn record_debug(&amp;mut self, field: &amp;tracing::field::Field, value: &amp;dyn std::fmt::Debug) {
self.0.insert(
field.name().to_string(),
serde_json::json!(format!(&quot;{:?}&quot;, value)),
);
}
}
<span class="boring">}</span></code></pre></pre>
<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(
&amp;self,
event: &amp;tracing::Event&lt;'_&gt;,
_ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
// Covert the values into a JSON object
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(&amp;mut fields);
event.record(&amp;mut visitor);
// Output the event in JSON
let output = serde_json::json!({
&quot;target&quot;: event.metadata().target(),
&quot;name&quot;: event.metadata().name(),
&quot;level&quot;: format!(&quot;{:?}&quot;, event.metadata().level()),
&quot;fields&quot;: fields,
});
println!(&quot;{}&quot;, serde_json::to_string_pretty(&amp;output).unwrap());
}
<span class="boring">}</span></code></pre></pre>
<p>继续运行:</p>
<pre><code class="language-properties">$ cargo run --example figure_3
{
&quot;fields&quot;: {
&quot;a_bool&quot;: true,
&quot;answer&quot;: 42,
&quot;message&quot;: &quot;first example&quot;
},
&quot;level&quot;: &quot;Level(Info)&quot;,
&quot;name&quot;: &quot;event examples/figure_3/main.rs:10&quot;,
&quot;target&quot;: &quot;figure_3&quot;
}
</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><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!(&quot;outer&quot;, level = 0);
let _outer_entered = outer_span.enter();
let inner_span = debug_span!(&quot;inner&quot;, level = 1);
let _inner_entered = inner_span.enter();
info!(a_bool = true, answer = 42, message = &quot;first example&quot;);
}</code></pre></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 -&gt; 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><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&lt;S&gt; Layer&lt;S&gt; 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&lt;'lookup&gt; tracing_subscriber::registry::LookupSpan&lt;'lookup&gt;,
{
fn on_event(&amp;self, event: &amp;tracing::Event&lt;'_&gt;, ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;) {
// 父 span
let parent_span = ctx.event_span(event).unwrap();
println!(&quot;parent span&quot;);
println!(&quot; name={}&quot;, parent_span.name());
println!(&quot; target={}&quot;, 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!(&quot;an ancestor span&quot;);
println!(&quot; name={}&quot;, span.name());
println!(&quot; target={}&quot;, span.metadata().target());
}
}
}
<span class="boring">}</span></code></pre></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><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&lt;S&gt; Layer&lt;S&gt; for CustomLayer
where
S: tracing::Subscriber,
S: for&lt;'lookup&gt; tracing_subscriber::registry::LookupSpan&lt;'lookup&gt;,
{
fn on_new_span(
&amp;self,
attrs: &amp;tracing::span::Attributes&lt;'_&gt;,
id: &amp;tracing::span::Id,
ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
let span = ctx.span(id).unwrap();
println!(&quot;Got on_new_span!&quot;);
println!(&quot; level={:?}&quot;, span.metadata().level());
println!(&quot; target={:?}&quot;, span.metadata().target());
println!(&quot; name={:?}&quot;, span.metadata().name());
// Our old friend, `println!` exploration.
let mut visitor = PrintlnVisitor;
attrs.record(&amp;mut visitor);
}
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-properties">$ cargo run --example figure_6
Got on_new_span!
level=Level(Info)
target=&quot;figure_7&quot;
name=&quot;outer&quot;
field=level value=0
Got on_new_span!
level=Level(Debug)
target=&quot;figure_7&quot;
name=&quot;inner&quot;
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&lt;String, serde_json::Value&gt;</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><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&lt;String, serde_json::Value&gt;);
<span class="boring">}</span></code></pre></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><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(
&amp;self,
attrs: &amp;tracing::span::Attributes&lt;'_&gt;,
id: &amp;tracing::span::Id,
ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
// 基于 field 值来构建我们自己的 JSON 对象
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(&amp;mut fields);
attrs.record(&amp;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::&lt;CustomFieldStorage&gt;(storage);
}
<span class="boring">}</span></code></pre></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><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(&amp;self, event: &amp;tracing::Event&lt;'_&gt;, ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;) {
let scope = ctx.event_scope(event).unwrap();
println!(&quot;Got event!&quot;);
for span in scope.from_root() {
let extensions = span.extensions();
let storage = extensions.get::&lt;CustomFieldStorage&gt;().unwrap();
println!(&quot; span&quot;);
println!(&quot; target={:?}&quot;, span.metadata().target());
println!(&quot; name={:?}&quot;, span.metadata().name());
println!(&quot; stored fields={:?}&quot;, storage);
}
}
<span class="boring">}</span></code></pre></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><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(&amp;self, event: &amp;tracing::Event&lt;'_&gt;, ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;) {
// 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::&lt;CustomFieldStorage&gt;().unwrap();
let field_data: &amp;BTreeMap&lt;String, serde_json::Value&gt; = &amp;storage.0;
spans.push(serde_json::json!({
&quot;target&quot;: span.metadata().target(),
&quot;name&quot;: span.name(),
&quot;level&quot;: format!(&quot;{:?}&quot;, span.metadata().level()),
&quot;fields&quot;: field_data,
}));
}
// The fields of the event
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(&amp;mut fields);
event.record(&amp;mut visitor);
// And create our output
let output = serde_json::json!({
&quot;target&quot;: event.metadata().target(),
&quot;name&quot;: event.metadata().name(),
&quot;level&quot;: format!(&quot;{:?}&quot;, event.metadata().level()),
&quot;fields&quot;: fields,
&quot;spans&quot;: spans,
});
println!(&quot;{}&quot;, serde_json::to_string_pretty(&amp;output).unwrap());
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-properties">$ cargo run --example figure_9
{
&quot;fields&quot;: {
&quot;a_bool&quot;: true,
&quot;answer&quot;: 42,
&quot;message&quot;: &quot;first example&quot;
},
&quot;level&quot;: &quot;Level(Info)&quot;,
&quot;name&quot;: &quot;event examples/figure_9/main.rs:16&quot;,
&quot;spans&quot;: [
{
&quot;fields&quot;: {
&quot;level&quot;: 0
},
&quot;level&quot;: &quot;Level(Info)&quot;,
&quot;name&quot;: &quot;outer&quot;,
&quot;target&quot;: &quot;figure_9&quot;
},
{
&quot;fields&quot;: {
&quot;level&quot;: 1
},
&quot;level&quot;: &quot;Level(Debug)&quot;,
&quot;name&quot;: &quot;inner&quot;,
&quot;target&quot;: &quot;figure_9&quot;
}
],
&quot;target&quot;: &quot;figure_9&quot;
}
</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><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!(&quot;outer&quot;, level = 0, other_field = tracing::field::Empty);
let _outer_entered = outer_span.enter();
// Some code...
outer_span.record(&quot;other_field&quot;, &amp;7);
<span class="boring">}</span></code></pre></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><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(
&amp;self,
id: &amp;tracing::span::Id,
values: &amp;tracing::span::Record&lt;'_&gt;,
ctx: tracing_subscriber::layer::Context&lt;'_, S&gt;,
) {
// 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: &amp;mut CustomFieldStorage =
extensions_mut.get_mut::&lt;CustomFieldStorage&gt;().unwrap();
let json_data: &amp;mut BTreeMap&lt;String, serde_json::Value&gt; = &amp;mut custom_field_storage.0;
// 使用我们的访问器老朋友
let mut visitor = JsonVisitor(json_data);
values.record(&amp;mut visitor);
}
<span class="boring">}</span></code></pre></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>
</blockquote>
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