NiloCK opened a new issue, #5871: URL: https://github.com/apache/couchdb/issues/5871
### Version unknown ### Describe the problem you're encountering CouchDB version: 3.4.3 (dpkg on Ubuntu, single-node) <img width="363" height="252" alt="Image" src="https://github.com/user-attachments/assets/49eb3a71-30a7-4ce9-bcce-17856f5f1a8b"; /> Above memory use is from an idle server - the drop off is a restart of couchdb via `systemctl restart couchdb`. ## Root cause: init_state/0 in couch_peruser.erl spawns a new mem3_cluster:start_link/4 process on every cluster_unstable cast and update_config cast. exit_changes/1 cleans up change feed handlers but never terminates the previous mem3_cluster process. Old mem3_cluster processes remain alive and continue firing cluster_unstable events, each triggering another init_state/0 call, creating a feedback loop of process accumulation. ## Evidence: Erlang remote shell inspection on the running node: - process_count climbed from 4,097 to 4,176 in ~2 minutes on an idle system (70 HTTP requests total since last restart) - erlang:process_info showed 16,426 couch_peruser:init_changes_handler processes accumulating - couch_event_server (the event dispatcher) was the top memory consumer at 8.3 MB, growing as it tracked all registered handlers ## Memory timeline (from system monitoring): - Post-restart: 3.2% RAM → 3.4% in 2 minutes - 6:14 PM: 39.7% → 2:24 AM: 87%+ (8 hours, +5.77%/hour) - Consistent across multiple restarts _system snapshots (3.6 minutes apart): ``` ┌───────────┬──────────────────────────┬────────────────────────────┐ │ Field │ Reading 1 (uptime 1593s) │ Reading 2 (uptime 1811s) │ ├───────────┼──────────────────────────┼────────────────────────────┤ │ processes │ 63,622,424 bytes │ 70,445,232 bytes (+6.8 MB) │ ├───────────┼──────────────────────────┼────────────────────────────┤ │ binary │ 787,440 │ 903,448 │ ├───────────┼──────────────────────────┼────────────────────────────┤ │ ets │ 1,302,568 │ 1,308,112 │ ├───────────┼──────────────────────────┼────────────────────────────┤ │ code │ 13,955,494 │ 13,955,494 │ └───────────┴──────────────────────────┴────────────────────────────┘ ``` ## Workaround: Disable couch_peruser (PUT _node/_local/_config/couch_peruser/enable → "false"). ### Expected Behaviour Steady state memory consumption for an idle server. ### Steps to Reproduce Haven't manually reproduced, but roughly: - init 3.4.3 db - enable couchdb per_user - create some dbs, users - observe ### Your Environment - Single-node CouchDB 3.4.3 (dpkg, Ubuntu 20.04) - 2 GB RAM - 97 databases (including ~80 userdb-* via couch_peruser) - Near-zero traffic - No active tasks, smoosh idle, no replication jobs ### Additional Context ## Related prior work: PR #3851 attempted a fix by unlinking the old mem3_cluster process, but reviewer @nickva noted it was insufficient — unlink without kill still leaves processes alive and sending events. nickva recommended keeping a single mem3_cluster process for the gen_server's lifetime and only restarting change feed handlers on state resets. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
