我们有一个使用辅助角色的云服务来处理从Azure Service Bus上设置的主题收到的消息。
消息本身似乎完好无损，通常会被正确接收和处理。但是，在某些情况下，消息似乎停止处理（Logging突然结束，并且在我们的WadLogsTable中看不到对正在处理的消息的更多引用）。根据我的研究，这可能是由于工作者角色保持其连接打开和闲置超过几秒钟而发生的。我如何防止这些长期过程的消息被抛弃？
我们的工作人员角色的代码如下。
public class WorkerRole : RoleEntryPoint
{
private static StandardKernel _kernel;
private readonly ManualResetEvent _completedEvent = new ManualResetEvent(false);
private BaseRepository<CallData> _callDataRepository;
private BaseRepository<CallLog> _callLogRepository;
private SubscriptionClient _client;
private NamespaceManager _nManager;
private OnMessageOptions _options;
private BaseRepository<Site> _siteRepository;
public override void Run()
{
try
{
List<CallInformation> callInfo;
Trace.WriteLine("Starting processing of messages");
// Initiates the message pump and callback is invoked for each message that is received, calling close on the client will stop the pump.
_client.OnMessage(message =>
{
// Process message from subscription.
Trace.TraceInformation("Call Received. Ready to process message ");
message.RenewLock();
callInfo = message.GetBody<List<CallInformation>>();
writeCallData(callInfo);
Trace.TraceInformation("Call Processed. Clearing from topic.");
}, _options);
}
catch (Exception e)
{
Trace.TraceInformation("Error: " + e.Message + "---" + e.StackTrace);
}
}
private void writeCallData(List<CallInformation> callList)
{
try
{
Trace.TraceInformation("Calls received: " + callList.Count);
foreach (var callInfo in callList)
{
Trace.TraceInformation("Unwrapping call...");
var call = callInfo.CallLog.Unwrap();
Trace.TraceInformation("Begin Processing: Local Call " + call.ID + " with " + callInfo.DataPoints.Length + " datapoints");
Trace.TraceInformation("Inserting Call...");
_callLogRepository.ExecuteSqlCommand(/*SNIP: Insert call*/);
Trace.TraceInformation("Call entry written. Now building datapoint list...");
var datapoints = callInfo.DataPoints.Select(datapoint => datapoint.Unwrap()).ToList();
Trace.TraceInformation("datapoint list constructed. Processing datapoints...");
foreach (var data in datapoints)
{
/*SNIP: Long running code. Insert our datapoints one at a time. Sometimes our messages die in the middle of this foreach. */
}
Trace.TraceInformation("All datapoints written for call with dependable ID " + call.Call_ID);
Trace.TraceInformation("Call Processed successfully.");
}
}
catch (Exception e)
{
Trace.TraceInformation("Call Processing Failed. " + e.Message);
}
}
public override bool OnStart()
{
try
{
var connectionString = CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");
_nManager = NamespaceManager.CreateFromConnectionString(connectionString);
_nManager.Settings.OperationTimeout = new TimeSpan(0,0,10,0);
var topic = new TopicDescription("MyTopic")
{
DuplicateDetectionHistoryTimeWindow = new TimeSpan(0, 0, 10, 0),
DefaultMessageTimeToLive = new TimeSpan(0, 0, 10, 0),
RequiresDuplicateDetection = true,
};
if (!_nManager.TopicExists("MyTopic"))
{
_nManager.CreateTopic(topic);
}
if (!_nManager.SubscriptionExists("MyTopic", "AllMessages"))
{
_nManager.CreateSubscription("MyTopic", "AllMessages");
}
_client = SubscriptionClient.CreateFromConnectionString(connectionString, "MyTopic", "AllMessages",
ReceiveMode.ReceiveAndDelete);
_options = new OnMessageOptions
{
AutoRenewTimeout = TimeSpan.FromMinutes(5),
};
_options.ExceptionReceived += LogErrors;
CreateKernel();
_callLogRepository.ExecuteSqlCommand(/*SNIP: Background processing*/);
}
catch (Exception e)
{
Trace.TraceInformation("Error on roleStart:" + e.Message + "---" + e.StackTrace);
}
return base.OnStart();
}
public override void OnStop()
{
// Close the connection to Service Bus Queue
_client.Close();
_completedEvent.Set();
}
void LogErrors(object sender, ExceptionReceivedEventArgs e)
{
if (e.Exception != null)
{
Trace.TraceInformation("Error: " + e.Exception.Message + "---" + e.Exception.StackTrace);
_client.Close();
}
}
public IKernel CreateKernel()
{
_kernel = new StandardKernel();
/*SNIP: Bind NInjectable repositories */
return _kernel;
}
}
答案 0 :(得分：1)
您的Run方法无法无限期地继续下去。它应该是这样的：
public override void Run()
{
try
{
Trace.WriteLine("WorkerRole entrypoint called", "Information");
while (true)
{
// Add code here that runs in the role instance
}
}
catch (Exception e)
{
Trace.WriteLine("Exception during Run: " + e.ToString());
// Take other action as needed.
}
}
取自docs：
“运行”被视为应用程序的主要方法。重写 不需要Run方法;从来没有默认的实现 回报。如果您覆盖Run方法，您的代码应该阻止 无限期。如果Run方法返回，则角色自动进行 通过提升Stopping事件并调用OnStop方法来回收 这样你的关机序列可以在角色之前执行 离线。</ p>
答案 1 :(得分：1)
TheDude的回答非常接近正确答案！事实证明，他认为run方法需要保持活着而不是立即返回。但是，使用Azure Service Bus的消息泵机制，您不能将_client.onMessage（...）放在while循环中，因为这会导致错误（消息泵已经初始化）。
实际需要发生的是需要在工作者角色开始执行之前创建手动重置事件，然后在执行消息泵代码之后等待。有关ManualResetEvent的文档，请参阅https://msdn.microsoft.com/en-us/library/system.threading.manualresetevent(v=vs.110).aspx。此外，此处描述了该过程：http://www.acousticguitar.pro/questions/607359/using-queueclient-onmessage-in-an-azure-worker-role
我的最终职员角色类看起来像这样：
public class WorkerRole : RoleEntryPoint
{
private static StandardKernel _kernel;
private readonly ManualResetEvent _completedEvent = new ManualResetEvent(false);
private BaseRepository<CallLog> _callLogRepository;
private SubscriptionClient _client;
private MessagingFactory _mFact;
private NamespaceManager _nManager;
private OnMessageOptions _options;
public override void Run()
{
ManualResetEvent CompletedEvent = new ManualResetEvent(false);
try
{
CallInformation callInfo;
// Initiates the message pump and callback is invoked for each message that is received, calling close on the client will stop the pump.
_client.OnMessage(message =>
{
// Process message from subscription.
Trace.TraceInformation("Call Received. Ready to process message " + message.MessageId);
callInfo = message.GetBody<CallInformation>();
WriteCallData(callInfo);
Trace.TraceInformation("Call Processed. Clearing from topic.");
}, _options);
}
catch (Exception e)
{
Trace.TraceInformation("Error: " + e.Message + "---" + e.StackTrace);
}
CompletedEvent.WaitOne();
}
private void writeCallData(List<CallInformation> callList)
{
try
{
Trace.TraceInformation("Calls received: " + callList.Count);
foreach (var callInfo in callList)
{
Trace.TraceInformation("Unwrapping call...");
var call = callInfo.CallLog.Unwrap();
Trace.TraceInformation("Begin Processing: Local Call " + call.ID + " with " + callInfo.DataPoints.Length + " datapoints");
Trace.TraceInformation("Inserting Call...");
_callLogRepository.ExecuteSqlCommand(/*SNIP: Insert call*/);
Trace.TraceInformation("Call entry written. Now building datapoint list...");
var datapoints = callInfo.DataPoints.Select(datapoint => datapoint.Unwrap()).ToList();
Trace.TraceInformation("datapoint list constructed. Processing datapoints...");
foreach (var data in datapoints)
{
/*SNIP: Long running code. Insert our datapoints one at a time. Sometimes our messages die in the middle of this foreach. */
}
Trace.TraceInformation("All datapoints written for call with dependable ID " + call.Call_ID);
Trace.TraceInformation("Call Processed successfully.");
}
}
catch (Exception e)
{
Trace.TraceInformation("Call Processing Failed. " + e.Message);
}
}
public override bool OnStart()
{
try
{
var connectionString = CloudConfigurationManager.GetSetting("Microsoft.ServiceBus.ConnectionString");
_nManager = NamespaceManager.CreateFromConnectionString(connectionString);
_nManager.Settings.OperationTimeout = new TimeSpan(0,0,10,0);
var topic = new TopicDescription("MyTopic")
{
DuplicateDetectionHistoryTimeWindow = new TimeSpan(0, 0, 10, 0),
DefaultMessageTimeToLive = new TimeSpan(0, 0, 10, 0),
RequiresDuplicateDetection = true,
};
if (!_nManager.TopicExists("MyTopic"))
{
_nManager.CreateTopic(topic);
}
if (!_nManager.SubscriptionExists("MyTopic", "AllMessages"))
{
_nManager.CreateSubscription("MyTopic", "AllMessages");
}
_client = SubscriptionClient.CreateFromConnectionString(connectionString, "MyTopic", "AllMessages",
ReceiveMode.ReceiveAndDelete);
_options = new OnMessageOptions
{
AutoRenewTimeout = TimeSpan.FromMinutes(5),
};
_options.ExceptionReceived += LogErrors;
CreateKernel();
_callLogRepository.ExecuteSqlCommand(/*SNIP: Background processing*/);
}
catch (Exception e)
{
Trace.TraceInformation("Error on roleStart:" + e.Message + "---" + e.StackTrace);
}
return base.OnStart();
}
public override void OnStop()
{
// Close the connection to Service Bus Queue
_client.Close();
_completedEvent.Set();
}
void LogErrors(object sender, ExceptionReceivedEventArgs e)
{
if (e.Exception != null)
{
Trace.TraceInformation("Error: " + e.Exception.Message + "---" + e.Exception.StackTrace);
_client.Close();
}
}
public IKernel CreateKernel()
{
_kernel = new StandardKernel();
/*SNIP: Bind NInjectable repositories */
return _kernel;
}
}
在Run方法结束时，您会注意到ManualResetEvent的存在以及WaitOne（）的调用。我希望有人觉得这很有帮助！