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Thread Management Playbook

Symptom: Cannot create or access chat threads.

Hypotheses

Hypothesis Likely Cause Evidence Tag
Participant limit Exceeded the maximum number of participants for a single chat thread [Measured]
Permission issues The user's token does not have the required chat scope [Observed]
Resource limits Exceeded the maximum number of chat threads per ACS resource [Correlated]
Concurrency conflict Multiple requests to update the thread were sent simultaneously [Inferred]

Evidence Collection

1. Browser Console

Look for 400 Bad Request or 403 Forbidden errors with a specific error code.

2. Service Limits

Review the ACS Chat Service Limits.

3. Log Analytics

Query the ACSChatThreadCreatedEvents table.

Validation

[Measured] Monitor Participant Count

Verify if the thread has reached the maximum of 250 participants. If exceeded, new participants cannot be added.

[Observed] Validate Token Scopes

Ensure the identity token was generated with the chat scope. Without it, thread creation will fail with 401 or 403.

[Correlated] Identify Resource Caps

If you're creating thousands of threads per second, you may hit the service-level throttling limits for ACS.

Mitigation

  1. Manage Participant List: Regularly prune inactive participants if the thread size approaches the limit.
  2. Assign Correct Scopes: Always include the chat scope when generating tokens for users.
  3. Handle Throttling: Implement exponential backoff for thread creation and update requests.
  4. Use Group Chat Wisely: Avoid creating new threads for the same group of users if an existing thread can be reused.

See Also

Sources

  • Azure Communication Services Chat Service Limits
  • Chat Architecture and Best Practices