Thread Management Playbook¶

Symptom: Cannot create or access chat threads.

Hypotheses¶

flowchart TD
    S["Thread create or update fails"] --> H1{"Participant count at limit?"}
    H1 -- yes --> R1["Reduce participants below service limit"]
    H1 -- no --> H2{"Token lacks thread permission?"}
    H2 -- yes --> R2["Reissue token with correct thread scopes"]
    H2 -- no --> H3{"Resource cap or concurrency conflict?"}
    H3 -- yes --> R3["Retry with backoff and audit quota"]
    H3 -- no --> EV["Collect evidence: browser console, service limits, Log Analytics"]
    EV --> M["Apply mitigation and re-run the operation"]

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¶

• Message Delivery
• Real-time Notifications

Sources¶

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