I have a system that sends a object to another service via WCF using MSMQ. The service picks the message up fine and does what it have to with it. But the problem i have now is that i need to send a response to the calling system.
Example:
Create a Customer object
Populate the information
Send the message to the service using WCF over MSMQ
Pick the message up from the queue using a windows service
Call Customer.Insert() method on the windows service
I now need to send the new customer id back to the calling application here.
Any ideas?
As Emmanuel points out - MSMQ messages are by design one-way and have no response, really.
Your best solution would be to have a response queue where the "other service" can drop his response messages into. Your client would then have to monitor that queue, e.g. check it once in a while (every minute, every 30 minutes - whatever makes sense for you) for new messages, and handle those.
There's no duplex (two-way) MSMQ channels - but you can easily create a pair of separate queues for both directions.
Marc
you can use duplex communication with msmq but not natively, take a look to my article
MSMQ Operation needs to one way, the only way I can think of receiving back a message is for your calling application to also Host a service for responses since there's no duplex MSMQ binding.
Related
I'm building a basic event based message system for a couple of services.
For my user service, I'm going to use a user topic exchange which will have routing keys like user.event.created, user.event.updated and user.event.deleted.
My logs service will consume user.event.* keys so I can log all events, whereas my email service will only listen for user.event.created as I'll only send out email on creation.
Now say I created a posts service, I want the logs service to consume events from here as well. Is it ok for me to bind both exchanges to the single logs.process queue?
Is there a better way of achieving this?
As long as each of the consume threads has it's own connection, it's fine. So, one thread consumes from topic exchange, the other from direct one etc.
As for the better part, I don't know - would require some more details.
I have some queries about WCF and multithreading.
My plan is to place items onto the Thread Pool and for it to process messages from the MSMQ queue.
I also will be hosting WCF in WAS.
I am wondering how the threading will work at this point. For example messages will be picked up by the WCF binding to the MSMQ queue and I know that WAS will spin up the service as and when it requires to. But lets say if we have 100 messages to process (100 messages per second for example) - would these be delivered in a threaded way or in a single thread?
If in a threaded manner then how best to commit or abort transactions? Any special considerations?
Sorry for the questions - just need to clarify this.
Its not clear what "placing items onto the Thread Pool" does but on the WCF side, a service using the netMsmqBinding handles "calls" in a similar way as other WCF bindings. The difference is that a "call" is actually an MSMQ message in a queue.
This article on netMsmqBinding gives a very clear explanation of how the binding works. If you configure the WCF service with its default InstanceContext setting (per call or per session depending on the .NET version), the service instances will pick up messages off the queue as-if they were a standard call each. There are setting in MSMQ and WCF that can affect this behavior to make the messages be processed sequentially but that's not the default.
Let WCF handle multi-threading for you by leaving the service set to per call (or per session) and for transactions, look at the code in this sample in MSDN to see how to work with them.
I am calling a WCF service which contains the business logic to process the message objects.
I need to pass the id of the message to WCF service. We are using MSMQ for queuing up the requests.
There could be multiple messages that WCF service need to process which can be handled as follows
Send the message id one by one
Send array of message ids and then WCF service will iterate through each id and process the message object.
Performance point of view I believe second option is better as multiple requests to WCF are not there.
Is my assumption correct?
-
Ram
Number 2 is more efficient in terms of latency but does not give you the chance to spread the processing load by having multiple queue readers
Also be aware that if you use a transactional queue and sessions then WCF may put more than one SOAP message in each MSMQ message
Just started learning NServiceBus and trying to understand the concept.
When it talks about queues, are we talking about MSMQs on both publisher and subscriber?
So, if I have an application that generates a list of something (say, name of animals), then it dumps the list into publisher’s queue. The publisher polls the queue every minute and if there is something in the queue, it will publish to subscriber’s queue for further processing. Does this make sense?
Thanks.
The sequence of events for a publish is as follows:
The Publisher will start up(Windows Service)
A Subscriber will start up and place a message into the Publisher's input queue(MSMQ)
The Publisher will take that message, read the address of the Subscriber and place that into storage(subscription storage: memory, MSMQ, or RDBMS)
When it is time to publish and event, the Publisher will inspect the type of message and then read subscription storage to find Subscribers interested in that message
The Publisher will then send a message to each of the Subscribers found in subscription storage
The Subscriber receives the message in its input queue(MSMQ) and processes it
You can leverage other messaging platforms instead of MSMQ, but MSMQ is the default. There really is no polling done, all the endpoints are signaled when a message hits the queues.
MSMQ is a transport layer. It passes the messages around.
The application will publish something using a NServiceBus queue. If you configured it to use MSMQ, that's what it will use for its transport layer and this is what the subscribers will be looking at.
NServiceBus follows the publisher/subscriber model as you have correctly stated. However your confusion is based on the use of two queues. This is incorrect. The server (publisher) will maintain the queue which is interfaced via the MSMQ protocol and so your application would communicate directly with this possibly remotely or locally.
You would typically use a WCF service which would raise an event upon a new message being pushed onto the queue. Your application can then make use of this new message as desired. See the NServiceBus documentation for examples: http://www.nservicebus.com/ArchitecturalPrinciples.aspx
I am shortly starting a project, which requires messages to be held in a queue for a period of 24 hours, this is because the database can't have any updates at certain times of the month. The service also has to be hosted on windows server 2003, which means it will have to be a windows service.
It is also required that the service use WCF so that in 12 months time when we move over to windows server 2008, the service can hosted in iis 7. At present I am wondering if MSMQ is the best way to handle this.
I've been looking into topics like poison message handling & dead letter queues, but nothing that really covers what I am intending to actually do. Could anyone recommend a sample or a tutorial for this ?
Thanks in advance
Yes, it sounds like this is a perfect scenario for WCF and MSMQ. It should be much easier to use MSMQ than to create your own queuing mechanism with the same robustness. You will want to look into the Message.TimeToBeReceived Property for a message expiring timeout.
If the interval specified by the TimeToBeReceived property expires
before the message is removed from the
queue, Message Queuing discards the
message in one of two ways. If the
message's UseDeadLetterQueue property
is true, the message is sent to the
dead-letter queue. If
UseDeadLetterQueue is false, the
message is ignored.
Here are some good starter tutorials on WCF with MSMQ: link1 and link2