Cosmos Synapse link SQL query error

Question

Hi, we have a Synapse SQL View onto a Cosmos container (using Synapse link). When we run a SELECT * on the view we sometimes get this error: Resolving CosmosDB path has failed with error 'CosmosDB request failed with status code '449'; {"code":"449","message":"SnapshotResourceHandler::GetStorageAccountSasUrisInternalAsync: Found expired SAS tokens, please retry.\r\nActivityId: e87e534c-0684-4e45-84d7-a02d6445c49e, http://Microsoft.Azure.Documents.Common/2.14.0"}

If we run the same SELECT query again there is no error.

We’ve tried recreating the container and the Synapse view.

Any ideas why we get this error?

Many thanks for any help. Regards, David

Answer 1

Hello David Baker,

Welcome to the Microsoft Q&A and thank you for posting your questions here.

Problem

Sequel to your questions, I understand that you are facing recurring errors code 449 related to SAS tokens when querying a Cosmos container through a Synapse SQL View. Despite recreating the container and the view, the issue persists, causing disruptions in data access and processing.

Scenarios

Putting myself in your shoe, I have to rewrite your unique scenario for more clearer understanding:

At a tech company, I oversee data pipelines and analytics processes. Our data setup involves using Azure services like Cosmos DB to store semi-structured data and Azure Synapse Analytics for querying and analyzing it. Lately, we've been encountering issues with some queries executed through Synapse SQL View. These queries directly access data in our Cosmos container via Synapse Link. Sometimes they fail, showing an error about expired SAS tokens along with a status code 449.

I've tried troubleshooting by recreating both the Cosmos container and the Synapse view, but unfortunately, the problem persists. These disruptions are impacting our data processing workflows. To address this, I'm seeking insights into why these tokens are expiring and suggestions on how to fix it. We need to ensure uninterrupted access to our data for analytics and reporting.

Solution

Firstly, to address this issue, after analyzing the error; the error you encountered shows that you have an expired SAS tokens when querying your Cosmos container through Synapse SQL View.

The error message indicates that the SAS tokens used for accessing your Cosmos container have expired, causing the query to fail. However, when you retry the query, new SAS tokens are generated, and the query succeeds. There could be several reasons why SAS tokens are expiring prematurely.

Kindly follow the below steps to solve this issue:

• Check the configuration of the SAS tokens used to access your Cosmos container. Ensure that the expiration time is set appropriately to accommodate the duration of your queries. You can adjust the expiration time when generating the SAS tokens.
• Set up a mechanism to automatically renew or refresh the SAS tokens before they expire. This can be achieved through code running either in your application or using Azure services such as Azure Functions or Logic Apps.

I provide a basic example below on how you might implement token renewal in Python using the Azure SDK for Cosmos DB:

from azure.cosmos import CosmosClient
import datetime
# Initialize Cosmos DB client with your connection details
cosmos_client = CosmosClient("<your_cosmosdb_endpoint>", credential="<your_cosmosdb_account_key>")
# Function to renew SAS token
def renew_sas_token(container_link):
    # Renew SAS token logic here
    # For example, generate a new SAS token with extended expiry
    expiry_date = datetime.datetime.utcnow() + datetime.timedelta(hours=24)
    new_sas_token = cosmos_client.generate_container_sas(container_link, permission="Read", expiry=expiry_date)
    return new_sas_token
# Usage example
container_link = "dbs/<your_database_name>/colls/<your_container_name>"
new_token = renew_sas_token(container_link)

• Ensure that the system clocks on your Synapse and Cosmos instances are synchronized to avoid any discrepancies that may cause tokens to appear expired due to clock skew.
• If your queries are being executed at a high frequency, consider optimizing them or adjusting rate-limiting settings to prevent hitting rate limits, which can lead to token expiration issues.
• Monitor your network for any transient issues or latency spikes that could affect token renewal. Additionally, keep an eye on the Azure status page for any ongoing incidents related to Cosmos DB or Synapse that could impact token generation or renewal.

Finally

By following the above steps and ensuring that SAS tokens are configured correctly, renewed before expiration, and addressing any potential issues with clock skew or query frequency, you can resolve the problem of expired SAS tokens when querying your Cosmos container through Synapse SQL View.

References

For more reading and leaning, kindly check the links by the right side of this page.

Accept Answer

I hope this is helpful! Do not hesitate to let me know if you have any other questions.

Please remember to "Accept Answer" if answer helped, so that others in the community facing similar issues can easily find the solution.

Best Regards,

Sina Salam

Answer 2

Hi @David Baker

Thanks for reaching out to Microsoft Q&A.

Based on the error message you provided, it seems like the SAS token used to access the CosmosDB container has expired. This can happen if the SAS token has a short lifespan or if the token has not been renewed.

Another possibility is Error '449' signifies transient error which should work fine if we try after some time.

To resolve this issue, you can try the following steps:

1. Check the expiration date of the SAS token used to access the CosmosDB container. If the token has expired, you can generate a new SAS token with a longer lifespan.
2. Verify that the Synapse link to the CosmosDB container is still valid. If the link has expired or is no longer valid, you can recreate the link.
3. Check if there are any network connectivity issues between Synapse and CosmosDB. You can try running the SELECT query again after a few minutes to see if the issue persists.
4. Ensure that the Synapse workspace and CosmosDB container are in the same region. If they are not in the same region, you may experience latency issues that can cause the error you are seeing.

More details on error: https://learn.microsoft.com/en-us/rest/api/cosmos-db/http-status-codes-for-cosmosdb

https://learn.microsoft.com/en-us/azure/cosmos-db/monitor?tabs=resource-specific-diagnostics

I hope this helps clarify the issue. Let me know if you have any further questions or concerns.