[PR] [Go] Fix resource leaks on client close [rocketmq-clients]

["guyinyou (via GitHub)" <gi...@apache.org>]

guyinyou opened a new pull request, #1305:
URL: https://github.com/apache/rocketmq-clients/pull/1305

   ## Problem
   
   When Go clients are repeatedly created and destroyed, resources leak:
   
   1. **Goroutine leak**: `GracefulStop()` only called `UnRegisterClient()` but never `shutdown()` on the per-client `ClientManager`, leaving 4 background goroutines (heartbeat, idle check, stats, sync settings) and RPC connections alive forever. This was a regression from #235 which made `ClientManager` per-client but forgot to add the shutdown call.
   
   2. **Telemetry session leak**: `endpointsTelemetryClientTable` sessions were never released on client close, leaking gRPC streaming connections.
   
   3. **Metrics cardinality explosion**: All clients shared global OpenCensus Views with `client_id` as a tag key. Each new client added new tag combinations that were never cleaned up, causing unbounded growth in metrics data.
   
   ## Fix
   
   1. **ClientManager shutdown**: Call `shutdown()` instead of `UnRegisterClient()` in `GracefulStop()` to stop background goroutines and close RPC connections.
   
   2. **Telemetry session cleanup**: Release all sessions in `GracefulStop()` before shutting down the client manager. Added nil check in `release()` for cases where the observer was never initialized.
   
   3. **Per-client metrics isolation**: Use `view.NewMeter()` (available since OpenCensus v0.22.4) to give each client its own Meter, Measures, Views, and Exporter. On client close, the Meter is stopped and views are unregistered. The `client_id` tag is preserved in exported metric data — the exported metric names and labels are unchanged.
   
   ## Test Results
   
   1000 iterations × 50 concurrent workers, each creating/sending/destroying a producer:
   
   | Metric | Master | Fix |
   |--------|--------|-----|
   | Goroutine leak | +13,814 | +385 |
   | Memory Sys | +342 MB | +17 MB |
   | Memory Alloc | +200 MB | +3.5 MB |
   
   Goroutines on fix branch stabilize after ~500 iterations (no linear growth), while master grows linearly at ~1,300 per 100 iterations.


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Re: [PR] [Go] Fix resource leaks on client close [rocketmq-clients]

["RongtongJin (via GitHub)" <gi...@apache.org>]

RongtongJin merged PR #1305:
URL: https://github.com/apache/rocketmq-clients/pull/1305


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