lumen日志及服务间调用trace链追踪源码阅读记录

框架初始化时，在最外层设置 try catch，便于捕捉异常。

---

protected function prepareDestination(Closure $destination)
{
    return function ($passable) use ($destination) {
        try {
            return $destination($passable);
        } catch (Exception $e) {
            return $this->handleException($passable, $e);
        } catch (Throwable $e) {
            return $this->handleException($passable, new FatalThrowableError($e));
        }
    };
}

捕捉到异常

---

$app->singleton(
    Illuminate\Contracts\Debug\ExceptionHandler::class,
    App\Exceptions\Handler::class
);

protected function handleException($passable, Exception $e)
{
    if (! $this->container->bound(ExceptionHandler::class) ||
        ! $passable instanceof Request) {
        throw $e;
    }

    $handler = $this->container->make(ExceptionHandler::class);

    $handler->report($e);

    $response = $handler->render($passable, $e);

    if (method_exists($response, 'withException')) {
        $response->withException($e);
    }

    return $response;
}

进到AppExceptionsHandler::class的report方法

---

public function report(Exception $e)
{
    if ($this->shouldntReport($e)) {
        return;
    }

    if (method_exists($e, 'report')) {
        return $e->report();
    }

    try {
        $logger = $this->container->make(LoggerInterface::class);
    } catch (Exception $ex) {
        throw $e; // throw the original exception
    }

    $logger->error(
        $e->getMessage(),
        array_merge($this->context(), ['exception' => $e]
    ));
}

registerCoreContainerAliases(） 设置了LoggerInterface::class的别名为log，查看AppServiceProvider文件

---

app()->instance('log', new \Illuminate\Log\Writer(
        $this, app()['events']
));

---

trace链

在每层的HEADER里定义了HTTP_X_TRACE_ID