I have a service that runs as an Azure Webjobs and scales out as needed, it's a long running process that can take a few hours for each message on the Queue. It works fine the only issue is that it relies on a third party for a rest endpoint that due to various issues can be unavailable.
My code catches this error and I need it to wait for 10-15seconds before it tries again, and I used
Thread.Sleep(10000);
This works locally but when in Azure as a webjob it seems to Pause all instances of the webjob not just the one that is needing to wait.
Any ideas as to why? each instance is on a difference thread I believe but I am relatively new to WebJobs so can't be 100% sure so some guidance on that would be good as well.
When you scale out the App Service Plan, All instances of the WebJob run independently. If they all sleep at the same time, it could be that the rest endpoint is generally unavailable during that time, leading all of them to sleep.
Related
I have this .NET long running API process/function that usually runs 30 mins in one execution that is hosted in AKS. This API is usually executed from the users coming from the front end of the app.
Due to concurrent executions from users, this is causing exhaustion of the app so I'm planning to implement a some sort of a queueing mechanism with the help of a scheduler(s).
What possibly is applicable Azure service that can execute my API in AKS on a scheduled basis (let's say every minute) and possibly check the database for some flagging values.
I need a way to check the table for some flagging value if there a currently running process or its been completed so it can process the next one, otherwise ignore the call until current on is complete.
I was looking into Azure Web Apps, Web Jobs or Batch Jobs but kinda confused which is applicable with my case.
Please advise thank you in advance.
There are a couple of options here.
Hangfire
Hangfire is an open-source library that can run background jobs in queues. In your case, you can enqueue each request from the client in a queue. Then Hangfire server will process them one by one (even with retry if the job fails). Hangfire supports SQL Server or Redis. You can query the storage to see the status of the queued jobs.
Hangfire can also run scheduled jobs, which will take care of that only one job run at a time.
Azure Service Bus
A more expensive option is to use Azure Service Bus for your queueing capability. For scheduled jobs, you can use AKS CronJobs but you will
implement the check yourself to see if there is a job already running.
Overall, I would recommend Hangfire, which can meet your requirements and is cheaper.
I have created 6 long running jobs in azure portal, before there was only 5 jobs, which all are working fine. But if I create 6th job, it causing issue like aborting all the jobs.
Azure service plan I am using is Standard: It say we can create max 50 jobs, still i am not able to. It is great if I got any solution for this, thanks in advance
I have experienced these symptoms. It may not be your particular cause, so you should do more digging to diagnose the problem.
In my case, a rogue job was exhausting TCP ports on the "plan." The plan is the PaaS abstraction that is served by one or more VM instances. There is no auto-scale or other alerting that really works related to TCP port exhaustion on Azure at the time of writing.
What you can do is add another App Service with its own long running process, on the same plan, and see if adding the 6th webjob on the other App Service kills all jobs on both app services.
If that is the case it means something plan-scoped is killing your jobs. This could be port exhaustion.
Another possibility is that you are deploying something as part of the webjob that is affecting the root web.config.
Can anybody explain the difference between Azure Web Jobs and Azure Scheduler
Azure Web Jobs
Only available on Azure Websites
It is used to run code at particular intervals. E.g. a console application every day
Used to trigger and run workloads.
Mainly recommended for workloads that either scale with the website or are relatively small.
Can be persistently running if "Always On" selected, otherwise you will get the 20 min timeout.
The code that needs to be run and schedule are defined together.
Azure Scheduler
Is not tied to Websites or Cloud Services
It allows you to call a website or add a message to a storage queue
Used for triggering events or triggering small workloads (e.g. add to queue), usually to trigger larger workloads
Mainly recommended for triggering more complex workloads.
This is only a trigger, and a separate function listening to trigger events (e.g. queue's) needs to be coded separately.
For many instances I prefer to use the scheduler to push to a storage queue and a worker role on each instance takes off the queue. This keeps tasks controlled granularly and can also move up or down in scale outside of your website.
With WebJobs they scale up and down with your site and hence your background tasks can become over taxed if your website is experiencing low traffic and scaled down.
Azure Scheduler - Provides a way to easily schedule http calls in a well-defined schedule, like every hour, every Friday at 9:00 am, Once a day, ...
Azure WebJobs - Provides a way to run small to medium work load (in the form of a script: .exe, .cmd, .sh, .js, ...) at the same context of an Azure Website (but can be hosted even with an empty website).
While a WebJob can run continuously (with a process that has a while loop) and Azure will make sure this WebJob is always running (with "Always On" set).
There is also an integration between Azure scheduler and Azure WebJobs where you have a WebJob that is running some finite work and the schduler is responsible for scheduling this work (invoking the WebJob).
So in summary, the scheduler is about scheduling work and WebJobs is about running work load.
I've got a continuously running WebJob on my auto-scale Azure website.
My WebJob is a simple console application with a while(true) loop that subscribes to certain messages on the Azure service bus and processes them. I don't want to process the same message twice, so when the web site is scaled an another WebJob is started I need for it to detect that another instance is already running and just sit there doing nothing until it's either killed (by scaling down again) or the other instance is killed. In the last scenario the second WebJob should detect that's the other is no longer take over.
Any takers?
You should create a queue (either using the Service Bus or storage queues) and pull the jobs off (create and manage a lease to the message) and process them from there. If that lease is managed properly, the job should only get processed once although you should make sure it's idempotent just in case as there are fringe cases where it will be processed more than once.
A very simple question:
Why would someone use the Azure Scheduler if Azure WebJobs are free?
I couldnt find any topic regarding "azure webjobs vs azure scheduler"
The main difference is that the webjob contains everything that the scheduler can do:
Scheduler can make HTTP calls
WebJob can do that and more (run SQL commands, etc)
The actual scheduling bits of WebJobs are built on top of the scheduler. When you set up a Web Job on a schedule under the hood it uses the scheduler to kick it off. WebJobs provides a nice little location to host the code that gets executed. In fact, if you create WebJobs for a web site look in the Scheduler on the portal and you'll see them listed there as well.
Also note that the scheduler could call out to other systems not running Azure. If you have something running in a Cloud Service that needs to be called regularly, or even if something was hosted elsewhere (another provider or on premises) the scheduler is where you can set that up.
Regarding the cost aspect, there is a free tier to the scheduler as well: http://www.windowsazure.com/en-us/pricing/details/scheduler/.
It's 2016. The below answers are no longer accurate.
WebJobs now also has a built-in scheduler and the schedule can be defined by a cron expression.
When publishing to Azure, you can choose if you want to have the WebJob sparked off by the Scheduler or by the WebJob internal scheduler.
Important Note: The Azure Scheduler has limits to frequency of either 1hr or 1min depending on if paid or not. For the internal scheduler however, your App Service requires Always On to keep on running and firing off the job. This Always On status may affect your pricing.
Continuous jobs are monitored, and if they exit they are re-executed. In this way they act more like "services" in your local machine. There is a module that monitors and keeps your app working. Always-ON is a feature that will help your site stay alive and hence, your webjobs to continuously run.
Scheduler is used to trigger the webjobs. It uses the scheduler user account (not the back-end account). This way you can move out of the free tier for scheduler, sign up to higher tiers to suit your needs. But essentially, all the scheduler is doing is hitting an https endpoint (which is public, but required your auth).
Triggered jobs (scheduled and on demand) are invoked by an https call. These calls are load balanced - much in the same way that a web app with many instances is load balanced. Continuous jobs run concurrently by default, but can be set to be a singleton.
For Webjobs starting from version 2, there is no reason to use an Azure Scheduler anymore. As a matter of fact, the Azure Portal already flags this functionality as (Legacy).
From WebJob SDK v2 additional triggers have been introduced and one of them is TimerTrigger, which works with CRON expressions to schedule executions. This execution mode does not need any additional Azure construct, you just need the webapp to be set as AlwaysOn to guarantee the webjob to run.
Another azure service that works with TimerTriggers is Azure Functions, which is built on top of the WebJob SDK that allows a serverless execution.