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Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. I would not have expected it to work either. I wonder if this is just a side effect of how blobTrigger implementation is done internally.
The way this works is actually through queues as well. There is a scanner that scans for blob changes and then pushes a message in a hidden queue, then that queue is consumed to actually process run your function on the blob. Listener ] guarantee only a single invocation across multiple hosts? It looks like it's not for me, because I see other instances starting up -- and blowing up because they are connecting to EventHub with a consumer group with an advanced epoch than the other consumer from the other instance.
You're using the wrong mode - you want the default SingletonMode. The listener mode singleton ensures that only a single host instance is running your function, however if there are many blobs that instance can process concurrently based on your concurrency settings.
Is this true? I've been working with Azure support on this and I'm not seeing this behavior. I have an EventHub triggered function with the Singleton annotation which, defaults to SingletonMode.
Function and I'm seeing multiple invocations. After talking to Azure support, it looks like the Singleton lock only applies per host. What type of function do you have? For this to work it has to be a precompiled annotated function, not a CSX style function. See more discussion here on current level of Singleton support: Behind the scenes, the singleton lock is based on a blob lease.
I have a compiled C function, and this comment from 5 days ago is the exact behavior I'm seeing: Singleton does not work with the Consumption plan: comment.
Azure Queue storage trigger for Azure Functions
For a precompiled C function, the singleton attribute is just passed to the underlying WebJobs SDK so should "just work". It also mentions the billing issue for Consumption. Currently I believe the time spent waiting for the singleton will be billed. Anyhow if you have a repro, recommend creating a new issue with all the specific details.
I expect your scenario to work, and if it isn't we can find out why from a repro. I have observed different behavior and I can try to put a repro together next week.
Azure Queue storage trigger and bindings for Azure Functions overview
I was advised by Azure support to switch to the App Service plan and away from Consumption to avoid this issue. I'm having the same issue.
Seems like every step of the way I run into unexpected issues with Azure services! I can't get Singleton to do anything useful at all on consumption plan. Didn't expect that to be the issue. I think I will have to use a timer or something to just manually process items in a queue if I really need them to be sequential. Contrary to what the documentation seems to indicate, I experimentally observed that, when on the consumption plan, the Singleton was only enforced per hostwhich means that under high load, when your instances to expand across multiple nodes, your singleton is only enforced once-per-node, resulting in multiple invocations, one per node.
To solve this, we used Azure Blobs, along with leases, to ensure that only one invocation for a given "application entity" was invoking at a particular time.Functions expect a base64 encoded string. Any adjustments to the encoding type in order to prepare data as a base64 encoded string need to be implemented in the calling service. Use the queue trigger to start a function when a new item is received on a queue.
The queue message is provided as input to the function. The following example shows a C function that polls the myqueue-items queue and writes a log each time a queue item is processed.
The following example shows a queue trigger binding in a function. The function polls the myqueue-items queue and writes a log each time a queue item is processed.
The configuration section explains these properties. The usage section explains myQueueItemwhich is named by the name property in function. The message metadata section explains all of the other variables shown. The name parameter reflects as context. This payload is also passed as the second parameter to the function. The following example demonstrates how to read a queue message passed to a function via a trigger.
A Storage queue trigger is defined in function. ServiceBusMessagewhich allows you to read the queue message in your function. The following Java example shows a storage queue trigger function, which logs the triggered message placed into queue myqueuename.
In C class librariesuse the following attributes to configure a queue trigger:. The attribute's constructor takes the name of the queue to monitor, as shown in the following example:. You can set the Connection property to specify the app setting that contains the storage account connection string to use, as shown in the following example:.
Provides another way to specify the storage account to use. The constructor takes the name of an app setting that contains a storage connection string. The attribute can be applied at the parameter, method, or class level. The following example shows class level and method level:. The QueueTrigger annotation gives you access to the queue that triggers the function. The following example makes the queue message available to the function via the message parameter.
The following table explains the binding configuration properties that you set in the function. When you're developing locally, app settings go into the local. Access the message data by using a method parameter such as string paramName. You can bind to any of the following types:.
If you try to bind to CloudQueueMessage and get an error message, make sure that you have a reference to the correct Storage SDK version. The paramName is the value specified in the name property of function.Learn how to create a function that is triggered when messages are submitted to an Azure Storage queue. Download and install the Microsoft Azure Storage Explorer.
An Azure subscription. If you don't have one, create a free account before you begin. From the Azure portal menu or the Home page, select Create a resource.
On the Basics page, use the function app settings as specified in the following table. Select Next : Hosting. On the Hosting page, enter the following settings. Select Next : Monitoring. On the Monitoring page, enter the following settings. Select the Notification icon in the upper-right corner of the portal and watch for the Deployment succeeded message. Select Go to resource to view your new function app.
You can also select Pin to dashboard. Pinning makes it easier to return to this function app resource from your dashboard. If this is the first function in your function app, select In-portal then Continue. Otherwise, go to step three. In the search field, type queue and then choose the Queue trigger template. If prompted, select Install to install the Azure Storage extension and any dependencies in the function app.
After installation succeeds, select Continue. Next, you connect to your Azure Storage account and create the myqueue-items storage queue. In your function, click Integrateexpand Documentationand copy both Account name and Account key.
You use these credentials to connect to the storage account in Azure Storage Explorer. If you have already connected your storage account, skip to step 4. Run the Microsoft Azure Storage Explorer tool, click the connect icon on the left, choose Use a storage account name and keyand click Next.
Enter the Account name and Account key from step 1, click Next and then Connect. Expand the attached storage account, right-click Queuesclick Create Queuetype myqueue-itemsand then press enter.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
Already on GitHub? Sign in to your account. We should discuss whether we want to bring this functionality forward for Functions. However, it will be relatively simple for us to do - we just need to expose new properties via function.
See here for singleton doc. In addition to Function level singleton support, we might also consider supporting Listener level Singleton as well.
Thanks vladkosarev. This issue has been on the back burner, since not many people have been asking for it yet. What specifically is your scenario? Being able to process messages from multiple queues in series as long as they affect the same entity. The idea here is having serialized access to data storage for a particular entity. I would love to see how efficient it's with using scoped singleton and Azure functions. Another option is to use Service Fabric, but it's huge piece of infrastructure to be handled.
Prefer to start with something as lightweight as Azure functions. That is exactly what I'm trying to achieve. Actor-like model using Azure functions. Now that they announced that functions will support serverless framework this might not be as important but I'd still like this ability in the 'raw'.
Service Fabric is great but it's still not serverless. I want to pay for compute resources not for VMs. Obviously you can't have in memory state, etc but it would still be a good start to the path of properly infinitely scalable architecture.
Based on the conversation here it seemed like it might be low hanging fruit. It would be extremely helpful to be able to specify singleton behavior in function. I have use case where this would very helpful. I have long running background processing tasks which are triggered via a storage queue. In order to prevent spikes in the database load, I need to ensure that that there is not more than one queue item being processed at a time.
My current solution is to use a timer trigger with a short interval to manually poll the queue, but a singleton flag for queue triggers would be a much tidier option.
Yes, I didn't know what this was from the title. Perhaps rename the report to something more descriptive. My case is just about the same. Would like to guarantee only one queue function running at a time.
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I thought that adding [Singleton] to a web job would force it to run one after another. This does not seem to be the case. When it runs I get this on the console:. Here is what I did to address this, like Haitham said in his answer [Singleton] refers to how many instances of the webjob itself is running -- not how many items are processed per instance.
Which when set to 1 only ran 1 at a time. When set to 2 like above then modifying the below code:. Produces this behavior which is what was expected :. Singleton does not mean it will run it one after another but mainly about instantiation the instance for the web job class. If you need to run just one at a time, you can use locks on a static variable to prevent the code to execute more than one time. But I would not recommend that anyway and you have to see why there are conflict errors.
Learn more. Asked 1 year, 1 month ago. Active 1 year, 1 month ago. Viewed 94 times. My understanding of this is obviously wrong, any clarification would be helpful. FirstOrDefault ; record. SaveChanges ; Console. What am I not understanding? ManagedThreadId; Console. Joe Ruder. Joe Ruder Joe Ruder 1, 1 1 gold badge 14 14 silver badges 35 35 bronze badges.The host.
This article lists the settings that are available starting with version 2. This article is for Azure Functions 2. For a reference of host. Other function app configuration options are managed in your app settings for deployed apps or your local. Configurations in host.
The following sample host. The following sections of this article explain each top-level property. All are optional unless otherwise indicated. Specifies how many function invocations are aggregated when calculating metrics for Application Insights.
Controls options for Application Insights, including sampling options.
Create a function triggered by Azure Queue storage
For the complete JSON structure, see the earlier example host. Log sampling may cause some executions to not show up in the Application Insights monitor blade. To avoid log sampling, add samplingExcludedTypes: "Request" to the applicationInsights value. For more information on snapshots, see Debug snapshots on exceptions in. Configuration setting can be found in Cosmos DB triggers and bindings. Configuration setting can be found in bindings for Durable Functions.
Configuration settings can be found in Event Hub triggers and bindings. Property that returns an object that contains all of the binding-specific settings, such as http and eventHub. Extension bundles let you add a compatible set of Functions binding extensions to your function app. To learn more, see Extension bundles for local development. Bundle versions increment as packages in the bundle change. Major version changes occur when packages in the bundle increment by a major version.
Major version changes in the bundle usually coincide with a change in the major version of the Functions runtime. The current set of extensions installed by the default bundle is enumerated in this extensions.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project?
Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. It also appears there is no lock file being created by the Consuming Function, only by the producer.
Windows Yes, SingletonAttribute is not supported in Azure Functions. We should add a warning to explain this. This would be nice to have from several aspects especially for those like me that need queue consumption in the order the message was put in.
Example: processing orders. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up.Azure Functions - Triggers & Bindings
New issue. Jump to bottom. Copy link Quote reply. This comment has been minimized. Sign in to view. Add Singleton support for Functions to ensure only one function running at a time Is this still the case?