I'm trying to put a Message back into an MSMQ when an exception is thrown. The following code appears to work but the Message is not put back in the queue?
Message msg = null;
try
{
MessageQueue MQueue = new MessageQueue(txtMsgQPath.Text);
msg = MQueue.ReceiveById(txtQItemToRead.Text);
lblMsgRead.Text = msg.Body.ToString(); // This line throws exception
}
catch (Exception ex)
{
lblMsgRead.Text = ex.Message;
if (msg != null)
{
MessageQueue MQ = new MessageQueue(txtMsgQPath.Text);
MQ.Send(msg);
}
}
Couple of points: The best way to do this would be using a transaction spanning both queues; that way you'll know you won't lose a message.
The second part of it is to be careful about how the queues are created and how you submit messages to the second queue. In particular, MSMQ sometimes appears to "fail silently" when sending a message (though in reality an error message is recorded elsewhere in the dead letter queues), particularly if the transactional options of the send don't match the transactional nature of the target queue.
Is it really your intention to send that message back to the originator? Sending it back to yourself is very dangerous, you'll just bomb again, over and over.
I believe that you're looking to "Peek" at the message. Use: MessageQueue.Peek and if you succeed, then consume the message.
I managed to get the code above to work by creating a new queue and pointing the code at the new queue.
I then compared the 2 queues and noticed that the new queue was multicast (the first queue wasn't) and the new queue had a label with the first didn't. Otherwise the queues appeared to be the same.
Related
I have a C# application that sets up numerous MQ listeners (multiple threads and potentially multiple servers each with their own listeners). There are some messages that will come off the queue that I will want to leave on the queue, move on to the next message on the MQ, but then under some circumstances I will want to go back to re-read those messages...
var connectionFactory = XMSFactoryFactory.GetInstance(XMSC.CT_WMQ).CreateConnectionFactory();
connectionFactory.SetStringProperty(XMSC.WMQ_HOST_NAME, origination.Server);
connectionFactory.SetIntProperty(XMSC.WMQ_PORT, int.Parse(origination.Port));
connectionFactory.SetStringProperty(XMSC.WMQ_QUEUE_MANAGER, origination.QueueManager);
connectionFactory.SetStringProperty(XMSC.WMQ_CHANNEL, origination.Channel);
var connection = connectionFactory.CreateConnection(null, null);
_connections.Add(connection);
var session = connection.CreateSession(false, AcknowledgeMode.ClientAcknowledge); //changed to use ClientAcknowledge so that we will leave the message on the MQ until we're sure we're processing it
_sessions.Add(session);
var destination = session.CreateQueue(origination.Queue);
_destinations.Add(destination);
var consumer = session.CreateConsumer(destination);
_consumers.Add(consumer);
Logging.LogDebugMessage(Constants.ListenerStart);
connection.Start();
ThreadPool.QueueUserWorkItem((o) => Receive(forOrigination, consumer));
Then I have...
if (OnMQMessageReceived != null)
{
var message = consumer.Receive();
var identifier = string.Empty;
if (message is ITextMessage)
{
//do stuff with the message here
//populates identifier from the message
}
else
{
//do stuff with the message here
//populates identifier from the message
}
if (!string.IsNullOrWhiteSpace(identifier)&& OnMQMessageReceived != null)
{
if( some check to see if we should process the message now)
{
//process message here
message.Acknowledge(); //this really pulls it off of the MQ
//here is where I want to trigger the next read to be from the beginning of the MQ
}
else
{
//We actually want to do nothing here. As in do not do Acknowledge
//This leaves the message on the MQ and we'll pick it up again later
//But we want to move on to the next message in the MQ
}
}
else
{
message.Acknowledge(); //this really pulls it off of the MQ...its useless to us anyways
}
}
else
{
Thread.Sleep(0);
}
ThreadPool.QueueUserWorkItem((o) => Receive(forOrigination, consumer));
So a couple of questions:
If I do not acknowledge the message it stays on the MQ, right?
If the message is not acknowledged then by default when I read from the MQ again with the same listener it reads the next one and does not go to the beginning, right?
How do I change the listener so that the next time I read I start at the beginning of the queue?
Leaving messages on a queue is an anti-pattern. If you don't want to or cannot process the message at a certain point of your logic, then you have a number of choices:
Get it off the queue and put to another queue/topic for a delayed/different processing.
Get it off the queue and dump to a database, flat file - whatever, if you want to process it outside of messaging flow, or don't want to process at all.
If it is feasible, you may want to change the message producer so it doesn't mix the messages with different processing requirements in the same queue/topic.
In any case, do not leave a message on the queue, and always move forward to the next message. This will make the application way more predictable and easier to reason about. You will also avoid all kinds of performance problems. If your application is or may ever become sensitive to the sequence of message delivery, then manual acknowledgement of selected messages will be at odds with it too.
To your questions:
The JMS spec is vague regarding the behavior of unacknowledged messages - they may be delivered out of order, and it is undefined when exactly when they will be delivered. Also, the acknowledge method call will acknowledge all previously received and unacknowledged messages - probably not what you had in mind.
If you leave messages behind, the listener may or may not go back immediately. If you restart it, it of course will start afresh, but while it is sitting there waiting for messages it is implementation dependent.
So if you try to make your design work, you may get it kind of work under certain circumstances, but it will not be predictable or reliable.
We have been using RabbitMQ as messaging service in the project. We will be pushing message into a queue and which will be received at the message consumer and will be trying to make entry into database. Once the values entered into the database we will be sending positive acknowledgement back to the RabbitMQ server if not we will be sending negative acknowledgement.
I have created Message Consumer as Windows service.Message has been successfully entered and well received by the message consumer(Made entry in table)but with an exception log "Shared Queue closed".
Please find the code block.
while (true)
{
try
{
if (!Connection.IsOpen || !Channel.IsOpen)
{
CreateConnection(existConnectionConfig, QueueName);
consumer = new QueueingBasicConsumer(Channel);
consumerTag=Channel.BasicConsume(QueueName,false,consumer);
}
BasicDeliverEventArgs e = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
IBasicProperties props = e.BasicProperties;
byte[] body = e.Body;
bool ack = onMessageReceived(body);
if (ack == true)
{
Channel.BasicAck(e.DeliveryTag, false);
}
else
Channel.BasicNack(e.DeliveryTag, false, true);
}
catch (Exception ex)
{
//Logged the exception in text file where i could see the
//message as "Shared queue closed"
}
}
I have surfed in net too but couldn't able to what the problem. It will be helpful if anyone able to help me out.
Thanks in advance,
Selva
In answer to your question, I have experienced the same problems when my Web Client has reset the connection due to App Pool recycling or some other underlying reason the connection has been dropped that appears beyond your scope. You may need to build in a retry mechanism to cope with this.
You might want to look at MassTransit. I have used this with RabbitMQ and it makes things a lot easier by effectively providing a management layer to RabbitMQ. MassTransit takes away the headache of retry mechanisms - see Connection management. It also provides a nice multi threaded concurrent consumer configuration.
This has the bonus of your implementation being more portable - you could easily change things to MSMQ should the requirement come along.
I am working on Azure queue. I need to get, process and delete all queue messages. What I am doing right now is calling the GetMessage, process the message and calling DeleteMessage one by one.
var message = _queue.GetMessage();
if (message == null)
{
return;
}
// processs
_queue.DeleteMessage(message);
Is there is a way to get all messages first then process it and delete all these processed messages?
You can't get all messages from a queue in a single call. Maximum number of messages you can Get from a queue in a single call is 32. So what you would need to do is something like:
var messages = _queue.GetMessages(32);
and then process these messages instead of getting one message at a time.
UPDATE
So a few things based on your comments:
A queue has a property called ApproximateMessages which will tell you approximately how many messages are there in the queue. This should give you an idea about the total number of messages.
You can't delete 32 messages in one shot. You will need to delete one message at a time.
Based on these, do take a look at pseudo code below:
do
{
var messages = _queue.GetMessages(32);
foreach (var msg in messages)
{
ProcessMessage(msg);
DeleteMessage(msg);
}
var approximateMessagesCount = _queue.FetchAttributes().ApproximateMessageCount.Value;
if (approximateMessagesCount == 0)
{
break;
}
} while (true);
Basically you have to keep on fetching messages from the queue (32 at a time), process individual message and once the message is processed then delete it. Once these 32 messages have been processed and deleted, you have to check if there are any more messages in the queue. If there are messages, you would repeat this process. If there are no messages, then you would exit out of the loop.
Current Setup includes a windows service which picks up a message from the local queue and extracts the information and puts in to my SQL database.According to my design
Service picks up the message from the queue.(I am using Peek() here).
Sends it to the database.
If for some reason i get an exception while saving it to the database the message is back into the queue,which to me is reliable.
I am logging the errors so that a user can know what's the issue and fix it.
Exception example:If the DBconnection is lost during saving process of the messages to the database then the messages are not lost as they are in the queue.I don't comit untill i get an acknowledgement from the DB that the message is inserted .So a user can see the logs and make sure that the DBconnection exists and every thing would be normal and we dont lose any messages in the queue.
But looking into another scenario:The messages I would be getting in the queue are from a 3rd party according a standard schema.The schema would remain same and there is no change in that.But i have seen some where i get some format exceptions and since its not committed the message is back to the queue.At this point this message would be a bottle neck for me as the same messages is picked up again and tries to process the message.Every time the service would pick up the same message and gets the same exception.So this loops infinitely unless that message is removed or put that message last in the queue.
Looking at removing the message:As of now if i go based on the format exception...then i might be wrong since i might encounter some other exceptions in the future .
Is there a way i can put this messages back to the queue last in the list instead beginning of the queue.
Need some advice on how to proceed further.
Note:Queue is Transactional .
As far as I'm aware, MSMQ doesn't automatically dump messages to fail queues. Either way you handle it, it's only a few lines of code (Bill, Michael, and I recommend a fail queue). As far as a fail queue goes, you could simple create one named .\private$\queuename_fail.
Surviving poison messages in MSMQ is a a decent article over this exact topic, which has an example app and source code at the end.
private readonly MessageQueue _failQueue;
private readonly MessageQueue _messageQueue;
/* Other code here (cursor, peek action, run method, initialization etc) */
private void dumpToFailQueue(Message message)
{
var oldId = message.Id;
_failQueue.Send(message, MessageQueueTransactionType.Single);
// Remove the poisoned message
_messageQueue.ReceiveById(oldId);
}
private void moveToEnd(Message message)
{
var oldId = message.Id;
_messageQueue.Send(message, MessageQueueTransactionType.Single);
// Remove the poisoned message
_messageQueue.ReceiveById(oldId);
}
I am new to activemq. T want to ask a question about the topics of Activemq. I succeed to get a message from a queue. Also I can send message to topic/Queue, but I can't get a message from Topic.
I have tried using Java Code. The result is the same.
The following is my core code:
connection.ClientId = clientId;
connection.Start();
using (ISession session = connection.CreateSession())
{
ITopic topic = new Apache.NMS.Commands.Topic(topicName);
IDestination destination = SessionUtil.GetDestination(session, topicName,
DestinationType.Topic);
using (IMessageConsumer consumer = **session.CreateDurableConsumer**(topic, "news", null, false))
{
**consumer.Listener += new MessageListener(consumer_Listener);**
//**IMessage iMsg = consumer.Receive();**
// if (iMsg != null)//{
// ITextMessage msg = (ITextMessage)iMsg;
// return msg.Text;
// }
//else
//return iMsg;
}
}
I also using: IMessage iMsg = consumer.Receive();
IMsg always null（topicname has messages. How can I consume topic's message?
The Messages would need to have been sent after the Topic consumer was created. A Topic is fire and forget, if there are no consumers then the message is discarded. Any consumer that comes online will only receive message sent after that time unless it is either a Durable Topic consumer or a Queue consumer.
In the case of a durable consumer you must have created an instance of it so there is a subscription record before those message were sent to the Topic. So I would guess your problem is that you didn't subscribe this consumer before and so the Broker was not storing any Messages for it.
I was so stupid about the phrase "using".Beacause I use "using" open connection and session. when the code block was excuted, the connnection/session is disappear. Now I dont use "using" block to cerate connection. just like normal code. It works. also I build "Global.asax" file. The program can listener Topic once started up. At the same time, I write a function to colse the connection.I tested. Once a message was sent to the topic, the Onessage() function would be exectued.
just resolve my problem.maybe you would have better answer.Thanks Tim.