I have 2 roles in my Azure cloud service application: a web role (signalr connections here) and a worker role.
The web role uses Azure service bus as its scaleout provider.
At certain points in time the worker role will emit certain events. I'd like to send this data directly to clients connected to a Hub.
My current implementation involves the worker role placing a message on a service bus queue which the web role subscribes to, the web role then forwards this message to clients via a HubContext call.
My question is: how can I send this message directly to connected clients from the worker role? So far I have considered 3 methods:
Configure signalr as in the web role so that they use the same servicebus topic. - this done not work as intended as worker role instances "steal messages" from topic subscriptions intended for the web role. This would seem to be the cleanest way of doing it but configuration is a problem.
Use the .Net client to send a hub message - this is not ideal as it places unnecessary load on the web role, as well as double the amount of service bus messages when compared to the above method.
Manually write a signalr compatible message to the topic - very hacky and succeptable to breaking changes.
I know that the team are currently rewriting scaleout for the next release but will this be possible at some point?
Edit:
I have noticed that this is supported in the RabbitMq implementation.
It seems an issue with my configuration was responsible for the first method not working.
However, it seems like that method is slower end to end (by about 150 ms) even with one less message in the loop.
I will wait and see if the scaleout work brings any improvements to this method before making any changes.
Related
I have an architectural question with signalR
Let's say I have a web app (pure front JS) that use a web api and the web app query an API that do a long task and want to be notified when the task is finished.
So the web api create a fire and forget task, and we use SSE with signalR to notify the web app. It's working. Great, thanks to signalR.
But now, I want the long task to be run in another process, let's say with a msmq based system.
So, the web app query the API, the web api create a message, and the msmq service process the message asynchronously.
Can the msmq service hosted in another process (maybe another machine !) notify the web app that the task is finished ? It can be possible to put the connection id in the message, but the service can be able to send the notification ?
I would use a servicebus, you can then use this library to forward the message directly to the clients.
https://github.com/AndersMalmgren/SignalR.EventAggregatorProxy
I have an ASP.NET website with a a number of long-running (5 mins to 2 hours) user-initiated tasks. I want each user to be able to see the progress of there own jobs, and be able to close their browser and return at a later time.
Current plan is to store each job in the database when it's started and publish a message to a RabbitMQ queue, which a windows service will receive and start processing the job.
However, I'm not sure of the best way to pass the progress information back to the webserver from the service? I see two options:
Store the progress information in the database, and have the web-app poll for it
Have a RabbitMQ consumer in the webserver and have the windows service post progress messages to that queue
I'm leaning towards the second option, as I don't really want to add more overhead to the database by regular polling / writing progress info. However, there are lots of warnings about using RabbitMQ (as a consumer) - as I am not sending vital messages (it doesn't matter if progress messages aren't processed), I'm wondering if this matters? It's not that (famous last words) difficult to restart the RabbitMQ consumer whenever the web app is restarted.
Does that option sound reasonable? Any better choices out there?
Store the progress information in the database, and have the web-app poll for it
Have a RabbitMQ consumer in the webserver and have the windows service post progress messages to that queue
the correct answer is C) All Of The Above!
A database is not an integration layer for applications.
RabbitMQ is not meant for end-user consumption of messages.
But when you combine RabbitMQ with a database, you get beautiful things...
have your background service send progress updates through RabbitMQ. the web server will listen for these updates and write the new status to the database. use websockets (signalr) to push the progress update to the user immediately, but you still have the current status in the database in case the user does a full refresh of the page or comes back later.
i wrote about this basic setup in a blog post on using rabbitmq to do user notifications
I have an Azure web application (Asp.net MVC & WebAPI) that sends emails through SendGrid service. I'm not using SendGrid's API but rather use .net built-in SMTP that I configured in web.config and directed to SendGrid.
I'm now wondering whether I also need message queueing application in my solution that would be used to actually send emails to SendGrid to minimize request/response times of my web app?
Azure already has Queue Storage that I could use but I wonder how others have implemented this? I'm also looking for the most simple example of Azure web app using queueing if one exists.
I expect message queueing will become relevant when I'll have several emails to send during single request to make my app scalable. Currently I'm sending email synchronously when my backend executes code and so far with the low number of emails it works fine.
If your application need to manage and send bulk emails asynchronously, it would be better to have separate application which will take emails as bulk.
In my recent project, I have created separate application using web role, worker role and a service bus queue. Web role is a web API which used for application to post bulk emails and put it into a service bus queue. Then worker role will be responsible for dealing with the queues and send the emails. This allowed me to send emails asynchronously and storing any email messages or message status in a table storage.
Further, this approach helps me to use same notification application (email sending application) in different projects by using a wrapper to handle web api integration.
I am having trouble wrapping my head around whether or not my scenario will require scale out. I have a process in a windows service that pushes messages to a hub hosted in a web app via the signalr .net client. These are user specific messages and are distributed using the Client(connectionid) approach. If this is deployed in a web farm scenario will I need to use a scale out approach? When a user joins I am storing that connection info in the database. I store the url of the webserver and connectionid so I can target that when I publish messages from the windows service.
I would use this if it is an option.
http://www.asp.net/signalr/overview/performance/scaleout-with-windows-azure-service-bus
Louis
We have this Pub/Sub system that you subscribe to via a callback mechanism in C# to recieve events from various things that happen within the database. This subscription has a callback signature attached to it that allows for the Pub / Sub system to callback any subscribers it has and notify them of the change on that Callback thread.
We are taking our windows application and migrating it into a web application. In doing so, I need a way to update this Web Application (The clients) with information from this Pub / Sub. I want to use SignalR, but not sure where to host it. I assume if I host it on the same Web Application as the Client, it won't be able to subscribe to the pubsub due to it not being able to do background threading.
Currently, I have it in a Console application hosting the SignalR server on a specific port. Obviously this is for testing and not ideal for a larger scale.
My question is.. is it really safe to be hosting SignalR outside of IIS? should I put this in a Windows Service? Web Service somehow? Can it go in a Web Application somehow?