Azure WebJob日志记录使主机崩溃，我们该怎么办？

Question

我们正在使用Azure运行多个WebJob。 我们的WebJob函数之一具有以下签名：

public static Task ProcessFileUploadedMessageAsync(
    [QueueTrigger("uploads")] FileUploadedMessage message,
    TextWriter logger,
    CancellationToken cancellationToken)

此功能正在监视队列中是否有消息指示文件已上传，然后触发文件数据的导入。 请注意，将TextWriter用作第二个参数：这是由WebJobs API基础结构提供的。

我们的导入过程有点慢（在某些情况下，单个文件的导入可能要花几个小时），因此我们会定期（通过TextWriter ）将消息写入日志以跟踪进度。 不幸的是，由于日志记录异常，我们较大的文件导致WebJob托管过程终止。 这是来自托管进程日志的示例堆栈跟踪：

[04/02/2016 03:44:59 > 660083: ERR ] 
[04/02/2016 03:45:00 > 660083: ERR ] Unhandled Exception: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
[04/02/2016 03:45:00 > 660083: ERR ] Parameter name: chunkLength
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Text.StringBuilder.ToString()
[04/02/2016 03:45:00 > 660083: ERR ]    at System.IO.StringWriter.ToString()
[04/02/2016 03:45:00 > 660083: ERR ]    at Microsoft.Azure.WebJobs.Host.Loggers.UpdateOutputLogCommand.<UpdateOutputBlob>d__10.MoveNext()
[04/02/2016 03:45:00 > 660083: ERR ] --- End of stack trace from previous location where exception was thrown ---
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at Microsoft.Azure.WebJobs.Host.Loggers.UpdateOutputLogCommand.<TryExecuteAsync>d__3.MoveNext()
[04/02/2016 03:45:00 > 660083: ERR ] --- End of stack trace from previous location where exception was thrown ---
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at Microsoft.Azure.WebJobs.Host.Timers.RecurrentTaskSeriesCommand.<ExecuteAsync>d__0.MoveNext()
[04/02/2016 03:45:00 > 660083: ERR ] --- End of stack trace from previous location where exception was thrown ---
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
[04/02/2016 03:45:00 > 660083: ERR ]    at Microsoft.Azure.WebJobs.Host.Timers.TaskSeriesTimer.<RunAsync>d__d.MoveNext()
[04/02/2016 03:45:00 > 660083: ERR ] --- End of stack trace from previous location where exception was thrown ---
[04/02/2016 03:45:00 > 660083: ERR ]    at Microsoft.Azure.WebJobs.Host.Timers.BackgroundExceptionDispatcher.<>c__DisplayClass1.<Throw>b__0()
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
[04/02/2016 03:45:00 > 660083: ERR ]    at System.Threading.ThreadHelper.ThreadStart()
[04/02/2016 03:45:00 > 660083: SYS ERR ] Job failed due to exit code -532462766
[04/02/2016 03:45:01 > 660083: SYS INFO] Process went down, waiting for 0 seconds
[04/02/2016 03:45:01 > 660083: SYS INFO] Status changed to PendingRestart

主要问题在于，此异常不是由我们的代码而是由WebJobs API中的某些东西引发的：

at Microsoft.Azure.WebJobs.Host.Loggers.UpdateOutputLogCommand.<UpdateOutputBlob>d__10.MoveNext()

我们尝试在对TextWriter的调用周围放置try...catch块，但这些没有效果。 看来日志消息被缓冲在某个位置，并通过一个单独的线程定期刷新到Azure blob存储。 如果是这种情况，那么我们将无法捕获异常。

是否还有其他人遇到相同的问题，或者有人可以考虑可能的解决方案或解决方法？

---

为了完整TextWriter ，这是我们使用TextWriter进行记录的方式：

await logger.WriteLineAsync("some text to log");

没有比这更复杂的了。

---

更新 ：似乎这已在WebJobs SDK GitHub上报告为问题＃675 。

Answer 1

您应该向方法添加async ，如下所示：

public async static Task ProcessFileUploadedMessageAsync(...)

要获取详细信息，您可以查看本文