TracingChannel 通道

【TracingChannel Channels】

TracingChannel 是多个 diagnostics_channel 的集合，表示单个可跟踪操作执行生命周期中的特定点。其行为分为五个 diagnostics_channel，包括 start、end、asyncStart、asyncEnd 和 error。单个可跟踪操作将在所有事件之间共享相同的事件对象，这对于通过 weakmap 管理关联非常有用。

【A TracingChannel is a collection of several diagnostics_channels representing specific points in the execution lifecycle of a single traceable action. The behaviour is split into five diagnostics_channels consisting of start, end, asyncStart, asyncEnd, and error. A single traceable action will share the same event object between all events, this can be helpful for managing correlation through a weakmap.】

当任务“完成”时，这些事件对象将会扩展包含 result 或 error 的值。对于同步任务，result 将是返回值，而 error 则是函数中抛出的任何异常。对于基于回调的异步函数，result 将是回调的第二个参数，而 error 要么是在 end 事件中可见的抛出错误，要么是在 asyncStart 或 asyncEnd 事件中的第一个回调参数。

【These event objects will be extended with result or error values when the task "completes". In the case of a synchronous task the result will be the return value and the error will be anything thrown from the function. With callback-based async functions the result will be the second argument of the callback while the error will either be a thrown error visible in the end event or the first callback argument in either of the asyncStart or asyncEnd events.】

跟踪通道应遵循以下命名模式：

【Tracing channels should follow a naming pattern of:】

• tracing:模块.类.方法:start 或 tracing:模块.函数:start
• tracing:模块.类.方法:end 或 tracing:模块.函数:end
• tracing:模块.类.方法:asyncStart 或 tracing:模块.函数:asyncStart
• tracing:模块.类.方法:asyncEnd 或 tracing:模块.函数:asyncEnd
• tracing:模块.类.方法:错误 或 tracing:模块.函数:错误