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Implementing Retry Mechanism in Blob-Triggered Azure Function for Specific Errors – java

I have a blob-triggered Azure Function, and I want to implement a retry mechanism to handle scenarios where the function fails during execution due to a specific error.

The requirements are as follows:

  • The function should automatically retry processing the same blob when a specific error is encountered.
  • I don’t want to manually reload the file into the container to retrigger the function.

How can I set up such a retry mechanism in Azure Functions?

Any guidance or examples would be greatly appreciated!

Built-in retry behaviors of individual trigger extensions

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2

Answers


  1. 0

    Follow below steps to set up a retry mechanism in Java Azure Function:

    1. Use below code to configure retry policy that handle Errors in the Function Code and throw exceptions when a specific error is encountered. This will trigger the retry mechanism based on the configured policy, refer MSDOC.

    Code Snippet:

    public class BlobTriggerJava {
    @FunctionName("BlobTriggerJava")
    @StorageAccount("storageConnection")
    @FixedDelayRetry(maxRetryCount = 4, delayInterval = "00:00:10")
    public void run(
        @BlobTrigger(name = "content", path = "testkp/{name}", dataType = "binary") byte[] content,
        @BindingName("name") String name,
        final ExecutionContext context
    ) {
        context.getLogger().info("Processing blob: " + name);
        try {
            if (name.contains("error")) {
                throw new Exception("Simulated error");
            }
        } catch (Exception e) {
            context.getLogger().severe("Error processing blob: " + e.getMessage());
            throw new RuntimeException(e);
        }    }
}
    1. Define a retry policy in the host.json file which controls the implicit retries of your Azure Function. For example, you can use a fixed delay or exponential backoff strategy for retries, refer MSDOC and SO answer by @JesseSquire.

    host.json:

    {  
  "version": "2.0",  
  "extensions": {  
    "blobs": {  
      "poisonBlobThreshold": 1,  
      "maxDegreeOfParallelism": 4  
  }  
  },  
  "retry": {  
    "strategy": "fixedDelay",  
    "maxRetryCount": 3,  
    "delayInterval": "00:00:10"  
  }  
}

    Console Output:

    Functions:

    BlobTriggerJava: blobTrigger

For detailed output, run func with --verbose flag.
[2024-12-23T07:35:43.571Z] Host lock lease acquired by instance ID '000000000000000000000000F72731CC'.
[2024-12-23T07:35:46.945Z] Executing 'Functions.BlobTriggerJava' (Reason='New blob detected(LogsAndContainerScan): test/Hello World.txt', Id=b2ee3ba8-fc36-46ae-b8f5-31fc8e95201a)
[2024-12-23T07:35:46.947Z] Trigger Details: MessageId: 440a3afb-45a5-44a3-8b01-1ebe946874e6, DequeueCount: 1, InsertedOn: 2024-12-23T07:35:42.000+00:00, BlobCreated: 2024-12-23T06:47:20.000+00:00, BlobLastModified: 2024-12-23T06:56:54.000+00:00
[2024-12-23T07:35:47.236Z] Processing blob: Hello World.txt
[2024-12-23T07:35:47.236Z] Function "BlobTriggerJava" (Id: b2ee3ba8-fc36-46ae-b8f5-31fc8e95201a) invoked by Java Worker
[2024-12-23T07:35:47.262Z] Executed 'Functions.BlobTriggerJava' (Succeeded, Id=b2ee3ba8-fc36-46ae-b8f5-31fc8e95201a, Duration=1341ms)
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  2. 0

    Try this approach:

    Edit the host.json File: Add a retry configuration under functionTimeout for the blob trigger.

    {
  "version": "2.0",
  "retry": {
  "strategy": "fixedDelay",
  "maxRetryCount": 5,
  "delayInterval": "00:00:10"
}

    This will only be applied when there is an unhandled exception within your function code. If the error is being caught and handled within your code, the Azure Functions runtime will not consider it as a failure, and the retry policy won’t be triggered.

    To ensure that the retry policy is triggered when there is an error in the querying process, you should let the function throw an exception when an error occurs

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