Does AlloyDB Managed Connection Pooling solve connection issues during autoscaling?

[ryorm]

I've set up autoscaling for my AlloyDB instance following the guidance in this article. However, I'm experiencing connection drops from my application whenever the database scales up or down.

While I've implemented reconnection logic in my application, the system remains unstable during scaling events, causing disruptions to my service.

I'm wondering if enabling Managed Connection Pooling would solve this issue. The documentation mentions that it helps with "connection surges" and improves performance "especially with scaled connections", but doesn't explicitly state whether it maintains connections during scaling events.

Has anyone successfully used Managed Connection Pooling to maintain stable connections during AlloyDB autoscaling operations? Any configuration tips or best practices would be greatly appreciated.

Thank you!

[ms4446 · Accepted solution]

Please Note: AlloyDB does not currently support native autoscaling. The Blog post you referenced uses a combination of Cloud Monitoring, Pub/Sub, and Cloud Functions.  While this approach offers flexibility, it can introduce connection instability during scaling operations.

When an AlloyDB instance is vertically scaled or restarted, active connections may drop. This can trigger a "thundering herd" effect, where many clients simultaneously attempt to reconnect, placing significant strain on the system and potentially leading to service disruption.

Managed Connection Pooling in AlloyDB can mitigate these challenges by acting as a lightweight intermediary between the application and the database. Built on pgBouncer, the pooling layer maintains a persistent set of backend connections and handles surges in reconnection attempts efficiently. Although it does not prevent the underlying connection drops during a scaling event, it significantly improves recovery time and reduces user-facing errors.

The benefits of using Managed Connection Pooling include reduced connection churn, improved handling of high concurrency, and smoother reconnections. 

For optimal stability, it is recommended to enable Managed Connection Pooling, use transaction pooling mode, and avoid session-dependent operations such as temporary tables or session variables. Fine-tuning pool parameters like max_client_conn and idle timeouts, combined with implementing exponential backoff in retry logic, can further strengthen resilience. Load testing during simulated scaling events is also advised to verify system behavior.