Request Timeout on ADF Web Activity to Synapse

Question

Hello everyone!

I have a set of pipelines in Azure Data Factory (ADF) that trigger Synapse via a Web activity POST request. This setup worked until today around 11 AM CET, but now it’s throwing the following error:

Error calling the endpoint. Response status code: 'ClientSideException HttpStatusCode : 408, HttpStatusString: RequestTimeout'. More details: Exception message: 'NA - Unknown [ClientSideException] A task was canceled.'.Request didn't reach the server from the client. This could happen because of an underlying issue such as network connectivity, a DNS failure, a server certificate validation or a timeout. Url endpoint request timed out. Please make sure the endpoint response is within 1 minute and retry.

I am using AutoResolveIntegrationRuntime. Although switching to a self-hosted Integration Runtime (IR) temporarily resolved the issue, it is now throwing errors again.

Previously, this POST request took around 10 seconds to complete. Even after increasing the timeout to 5 minutes, the issue persists.

There are no warnings on Azure services, but nothing is making sense to me anymore.

If anyone has any insights, please share!

Answer 1

Hi ,

Thanks for reaching out to Microsoft Q&A.

A 408 Request Timeout error in ADF’s Web Activity, particularly when triggering Synapse, can be tricky to troubleshoot.

Here’s a structured approach to diagnose and address this:

• Verify if the Synapse endpoint itself is responsive by testing it outside ADF, e.g., using Postman or a simple script. This can confirm if the issue is specifically with ADF or the Synapse service itself. Look for any service-level or firewall rule changes that may have impacted the endpoint's accessibility.
• Although you used AutoResolveIntegrationRuntime (default Azure IR), connectivity issues can sometimes arise if the underlying node experiences a network delay or issue. However, if a self-hosted IR temporarily fixed the issue, it suggests an intermittent connectivity problem on the Azure IR network side.
• Ensure that your timeout settings in the Web Activity are set to 5 minutes or longer, as you did, to allow for extended processing times. Consider adding a retry policy to the Web Activity if you haven’t already. ADF’s Web Activity supports up to three retries with an exponential backoff mechanism, which could be helpful if this is an intermittent issue.
• DNS Resolution: Verify if the endpoint URL resolves correctly by conducting a DNS lookup. Intermittent DNS resolution issues can cause the request to fail, so confirm that the Synapse endpoint’s DNS is accessible from the IR location.
• Certificates and SSL Validation: Any recent changes to SSL/TLS policies on the endpoint could affect SSL handshakes, so ensure that certificate chains are intact and meet Azure’s validation requirements.
• If other services are making requests to Synapse, you may encounter throttling. Check Synapse’s usage metrics and logs to identify if you are hitting any concurrency or resource limits.
• Enable diagnostic logging in both ADF and Synapse to get detailed logs on the failure. These logs might provide more context, particularly about networking, connectivity, or other service-related errors. Use Log Analytics or a similar monitoring tool to track any patterns in latency, especially around the 11 AM CET timeframe when the issue started. I have listed out most of the options. This structured approach should help pinpoint the root cause, whether it’s on the ADF, Synapse, or network side.

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Answer 2

Hi Erik Martins Tonon ,

Thank you for confirming that the issue has been resolved.

It appears this may have been a transient issue making it difficult for us to provide a definitive root cause.

If you'd like to investigate further, we recommend creating a support ticket for an in-depth analysis. Please let us know if there’s anything else I can assist you with.

Kindly accept the answer by clicking on Accept answer button. Thankyou