open-webui/backend/open_webui
Classic298 d7674c5174
perf: bounded non-blocking session pool reaper, fewer blocking pool round trips (#28835)
* perf: stop the Socket.IO session pool blocking the websocket event loop

With WEBSOCKET_MANAGER=redis the session pool is a synchronous Redis client, so every call into it blocks the whole worker's event loop, not just the caller. Two paths did it constantly: the orphan reaper walked the pool one round trip per session with no await anywhere, freezing the loop for the entire sweep every cycle, and nearly every socket event re-read the sender's session back out of Redis. Other users' events and every in-flight generation on that pod wait behind both.

The reaper now walks the pool in HSCAN batches and deletes in bulk, yielding between batches, and no longer sleeps past half the lock TTL, which previously guaranteed a failed renew every cycle. The per-event reads are gone: Socket.IO events only reach the worker holding the connection, and that worker already saved the same session dict locally when the user authenticated, so it was asking Redis for its own data. The writes stay, since those are what other pods read.

Measured at 4000 users / 16 containers, Redis 1.1 ms away:

| | before | after |
|---|---|---|
| reaper sweep, 5k sessions | 5.6 s, loop frozen throughout | 62 ms, 4.2 ms worst block |
| same, crash recovery with every session expired | 11.5 s | 96 ms |
| heartbeat / usage ping / disconnect | 2 / 3 / 2 round trips | 1 / 2 / 1 |
| 50-member channel post | 50 round trips, 57.2 ms block | 0 round trips, 0.02 ms |
| loop time per wall second at rest | 103 ms (10.3%) | 67 ms (6.7%) |

The alternative, converting RedisDict to the async client, fixes the same paths with a far larger blast radius (every call site gains await, and `in`/`[]`/`del` cannot be awaited so the dict interface goes) and still round-trips for data already in memory. Two deliberate behaviour changes: a heartbeat re-adds a session the reaper already removed, so a tab that survives a stall recovers instead of staying out of the pool until it reconnects; and disconnect no longer skips Yjs document cleanup when the pool entry is already gone, which previously leaked that document's update log forever.

Closes #28172

* perf: cut disconnect and user session lookup pool round trips, harden the session reaper

Follow-up on top of the session pool reaper branch. With WEBSOCKET_MANAGER=redis two paths still blocked the worker's event loop on synchronous Redis calls. Every disconnect listed all models in use cluster-wide and fetched each one individually, one blocking round trip per model. Disconnecting all sessions of a user (admin role change or deletion) pulled the entire session pool in one HGETALL and decoded every entry in a single uninterrupted block.

Disconnect now fetches the usage pool once with items(), going from 2+N+M round trips to 2+M (N models in use cluster-wide, M models the session used), and its delete of an emptied model entry is KeyError-guarded because another node can remove the same key between snapshot and delete; unguarded, that race aborted the handler and skipped its Yjs document cleanup. The user session lookup reuses the reaper's HSCAN batches and yields to the loop between pages. The reaper previously died permanently on the first Redis connection error, on every node at once during an outage; it now logs, releases the lock and returns to retrying acquisition.

* refac: keep the socket pool perf work to the round trips

A review pass on this branch turned up four changes riding along with the round-trip work without belonging to it, so they are backed out here. The `disconnect` handler keeps its `if sid in SESSION_POOL:` guard, so USAGE_POOL and ydoc cleanup stay off the path for sockets that never authenticated. `RedisDict.set()` keeps its own inline HDEL. `get_session_ids_by_user_id` stays synchronous over one HGETALL, since it runs on user delete and role change rather than per message. The crash-resilience wrapper around the reaper loop is dropped; if that guard is worth having, it belongs in its own change.

What stays is the perf part. The reaper now sweeps the pool in bounded HSCAN batches and deletes expired sids with one HDEL per batch, down from HKEYS plus an HGET and a per-sid HDEL across the whole pool. The `disconnect` handler reads USAGE_POOL with a single HGETALL, down from HKEYS plus one HGET per model in use. Session lookups in the socket handlers come from the local Socket.IO store, which removes one Redis GET from every heartbeat, usage, channel and ydoc event.

Naming and annotations follow the file: `get_session_pool_batches` for the module's `get_` prefix, `RedisDict.pop_many` so both reaper branches use one word for removing keys, a named `SCAN_BATCH_SIZE`, and types on the new helpers.

* fix: invalidate the RedisDict write signature on batch delete

RedisDict.set() skips the write when the payload fingerprint matches the last one this process wrote, so a mutation that goes around set() has to clear that fingerprint. The new batch delete did not, leaving a stale fingerprint behind: the next refresh with identical content is treated as already written and silently skipped, so the hash stays empty.

Renamed pop_many to delete_many. In a dict emulation pop removes and returns; this returns nothing and cannot without an extra HMGET, so the name promised something it does not do. delete_many matches __delitem__ and the HDEL underneath. Its only call site is the session pool reaper, whose behaviour is unchanged: same fields deleted, same batching, same return.
2026-08-31 01:17:53 -04:00
..
data refac: mv backend files to /open_webui dir 2024-09-04 16:54:48 +02:00
internal refac 2026-08-30 21:36:17 -04:00
migrations chore: format 2026-08-25 16:53:53 -04:00
models refac 2026-08-31 00:41:11 -04:00
retrieval refac 2026-08-31 00:40:15 -04:00
routers perf: bounded non-blocking session pool reaper, fewer blocking pool round trips (#28835) 2026-08-31 01:17:53 -04:00
socket perf: bounded non-blocking session pool reaper, fewer blocking pool round trips (#28835) 2026-08-31 01:17:53 -04:00
static refac 2026-07-27 19:39:36 -04:00
storage refac 2026-07-31 17:41:14 -04:00
tools refac 2026-08-30 23:46:02 -04:00
utils refac 2026-08-31 01:06:15 -04:00
__init__.py perf: allow disabling websocket per-message-deflate (#28613) 2026-08-24 18:46:07 -04:00
alembic.ini fix: Alembic CLI commands from failing 2025-08-15 04:17:47 -04:00
config.py refac: consolidate the web fetch address checks onto the request path (#27823) 2026-08-25 11:15:48 -04:00
constants.py refac 2026-08-29 16:14:32 -04:00
env.py fix: bound extracted document metadata by the upload size limit by default (#29025) 2026-08-25 15:50:27 -04:00
events.py refac 2026-08-16 23:21:00 -07:00
functions.py fix: honor bypass_system_prompt on the pipe route (#28739) 2026-08-19 11:08:02 -07:00
main.py fix: serve module scripts and wasm assets with the correct MIME type (#29139) 2026-08-30 21:32:31 -04:00
tasks.py fix: stopping a response across instances on Redis Cluster (#29165) 2026-08-29 15:00:52 -04:00