Workflow with MSMQ and Buffered Receive - wcf

We are building Workflow Foundation service with .NET 4.5 and are attempting to use MSMQ to deliver messages that Workflow Service should process.
We have enabled Allow Buffered Receive in order to have messages wait for Workflow to be able to process them.
However, we've ended up with some weird kind of locks in our message folders (see the pictures).
There is no documentation whatsoever to explain this. What is this? Is it related to WF, WCF, MSMQ? Where to look for solution?

I have no idea about the locks but I decided to implement my own queuing solution within my workflow outside of MSMQ due to past issues with MSMQ. I found the following article that helped me implement a queuing solution using SQL Server Implementing Message Queues in Relation Databases
Using a variant of this technique, IIS 7.5 AutoStart, WWF bookmarks and Context Based Correlation I was able to implement a persistent queue within my workflow without using MSMQ. The nature of workflow makes queuing within the workflow very doable.

Related

How to use message queue with Windows phone 8 app?

I have a windows phone 8 application, which communicates with WCF service using basicHttpBinding. The service is hosted on IIS7 (and not using windows azure)
As the service may go down for any reason, I am exploring the use of message queues to increase the reliability of the system.
I have looked at NetMsmqBinding provided in WCF - but it looks like this binding is not supported by WP8 client.
I am also looking at using RabbitMQ, but cannot find any working example with WP8 client using WCF.
Please can anyone suggest what is the best way forward? Any sample code (or links) will be much appreciated.
Thanks
First off, netMsmqBinding cannot be used across the internet. This is because it uses MSMQ which is not exposed over http.
When you're making calls to a resource across the internet, unreliability is something you need to factor into your application. Because of the number of possible problems you can encounter, it's generally not a case of if, but when, there is a failure and it's how your application deals with this which is important.
Even so, there are things you can do to minimize the reliability issues you experience, one of which does involve queuing.
Where queuing can be useful is taking large, complex, and long running processes offline. Because calls to such processes implemented synchronously often time out, you can gain a lot of reliability by making the actual processing call asynchronous.
As an example, it would be fairly common to have the web server invoke some offline process via message queuing and return to the client that their request is being processed. Because doing this is inexpensive calls are far less likely to fail. Your problem then becomes one of how to return the response to the client once the offline processing has been done.

Can any queuing system trigger external Applications

Right now we have a queuing system(activemq) which is storing the messages. And we have written a separate java application that will read the queue and then trigger a exe to do some processing. But we want to do away with this extra application that is linking our activemq and exe. So i want to know whether any queuing system houses a code which will help me run the exe without any extra code written by me.
Any inputs regarding which queuing system can get me this done will be greatly appreciated.
This isn't really how Message Brokers work. You could however embed a broker inside your own application or create a broker plugin to do something. In the end though the best way to do this is to create your own client that can implement your business logic and let the Message Broker do what it was designed to do, route message traffic.
If you want more of a 'push' solution rather than a producer-consumer solution (which sounds to me like you are) you could look into the use of WebSockets. That would be another way of dealing with messages.
As others have said it doesn't look like using a message broker is the solution you want if you don't want to have some additional middleware to provide asynchronous communication.
So you just need something to launch an EXE on message arrival?
Message Queuing Triggers
Just some additional information for you... Triggered applications are natively supported in IBM Websphere MQ via a Trigger Monitor application that runs as a service (in windows implementations) or a daemon (in UNixish implementations).
When a message arrives in a queue, the MQ software will generate another message ("Trigger" message and send it to the "Trigger" queue, which is being monitored by the Trigger Manager app. The app then starts the required application.
So your implementation of an "app to start an app" is not odd ball or strange at all.. IBM do it in their implementation. I see nothing wrong with your implementation and if you can integrate it tighter to activeMQ then you are on a winner.
What about IBM MQ's triggering feature ?
WebSphere MQ provides a feature that enables an application or channel to be started automatically when there are messages available to retrieve from a queue. A message is put to a queue defined as triggered. If a series of conditions are met, the queue manager sends a trigger message to an initiation queue.
https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.0.0/com.ibm.mq.dev.doc/q026940_.htm

NServiceBus vs Windows ServiceBus

Would someone be able to shed some light on the differences between the newly release Windows ServiceBus (on premise, not Azure) and NServiceBus?
Looking for a detailed answer what the windows SB may be missing as I'm familiar what NSErviceBus can do:
Is it a real service bus and not just a message broker that uses queues?
Can it support message polymorphism? (Messages subclassing other
messages and handlers supporting this hierarchy
Long running processes and correlation
Scale out
I'm responsible for the Windows Azure ServiceBus support in NServicebus. And in my opinion this new Windows Server Servicebus provides the exact same capabilities as the Azure ServiceBus. So in my opinion it will be a good match with NServiceBus instead of a competitor (just as the Windows Azure ServiceBus is) and could be used instead of msmq.
To answer your questions
The new servicebus is a broker that uses queues
Messages on the servicebus are just strings in the end, the servicebus itself has no additional support for message types, hierarchies, handlers etc. Typically you would use WCF or NServiceBus for this.
There is no support for long running processes nor correlation. It does have some feature overlap with NServiceBus though as it can do subcriptions/topics, it can also do deferral of messages as well as filters.
It's designed to scale out.
Hope this helps?
Kind regards,
Yves

To get messages with NServiceBus do you have to have a message queue on the subscribing machine?

I am wondering if there is a way to setup NServiceBus so that the machine actually getting the message from a publisher does not have the InputQueue on it. Also, I would like to publish to a general queue (though this can be accomplished with a web service.)
I am thinking I may use this to allow client machines to post and receive events. But the client machines are fairly locked down. If I need to have queues created on them I can, but it would be easier to have the queues uniquely named and in a more central location.
I am new to NServiceBus and pub/sub in general. So if I am off base on what I want please say so.
This sounds like the perfect candidate for an alternate queuing infrastructure beyond MSMQ--such as Azure Queues or Amazon SQS. With those types of queues you have no infrastructure to install on the client machines and everything is much more centralized.
Before you go down that road though, you'll want to get the basics of publish/subscribe under you. Pub/sub using MSMQ and NServiceBus has a decent learning curve to it and if you aren't familiar with how things work at that level then moving to cloud queues may be even more tricky.

What are the advantages of using WCF over frameworks like MassTransit or hand written MSMQ client?

I am looking at using MSMQ as a solution to do asynchronous execution in my upcoming project. I want to know the differences between using WCF and frameworks like MassTransit or even hand written MSMQ client to place/read task off MSMQ.
Basically the application will be several websites (internal through LAN or external through the Internet) reading/writing data through a service layer (be it WCF or normal web service). Then this service layer will do one of two things: 1. write data to database 2. and/or trigger the background process by placing a message in the queue. 3. obviously it can also retrieve data from database. The little agent (a windows service) on the other side of the queue will monitor the queue and execute based on the task command.
This architecture will be quite easy to scale (add more queues and agents) and easy to implement compared to RPC or distributed execution or whatever. And the agent processing doesn’t need to be real time. And the agent and service layer are separate applications except they share the common domain objects and Repositories etc.
What do you think? Architecture suggestions for the above requirements are welcomed. Thank you!
WCF adds an abstraction over MSMQ. In fact, once you define compatible contracts (operations must be OneWay), you can switch out MSMQ in the config, transparently. (For instance, you could switch to normal HttpWS or a NetTcp binding.)
You should evaluate the other WCF benefits, like security and so on, to see how those fit in with your needs. Again, they should be reasonably transparent of the fact you're using MSMQ underneath. For instance, adding SOAP security and so on should "just work", independent of using MSMQ.
(Although, IIRC, you still need to login to the desktop on each machine that uses MSMQ, with the service account that will use MSMQ, to generate the certificate in the machines local profile. And then, it doesn't work very well from IIS6, since user profiles aren't loaded. A real pain in general, but nothing to do with WCF specifically.)
Apart from that:
Have you looked at SQL Server Service Broker? After using MSMQ + WCF and SSSB, I think that SSSB is vastly easier to configure and manage. SSSB works with T-SQL commands over any SQL client (I use it from Mono, on Linux, with transactions). It'll also give you transactional send/receive, even remotely (I think MSMQ 4 now allows this). It really takes a lot of the pain away from message queuing, and if you're using SQL Server already...
SSSB is often overlooked since the SQL Management Studio doesn't have GUI designers for it all, but it isn't hard and is a great option. The one downside is that if you want local send capability (i.e., queue message when network is down), you'll need to run a local SQL Express instance.
Your architecture seems sound and reasonable. However you should consider using the WCF net MSMQ transport over hand coded MSMQ classes. WCF wraps this common functionality into a nice programming model. Also I believe there is some improvements in the protocol used by wcf compared to basic System.Messaging
Have a look at the value-add over plain MSMQ:
http://readthedocs.org/docs/masstransit/en/latest/overview/valueadd.html
In summary, you get a lot of messaging concepts clearly presented in the API with MassTransit; to an extent you wouldn't have if you hand-coded it or used WCF.