[GH-ISSUE #21410] bug: Memory leak in SESSION_POOL, USAGE_POOL and YdocManager (with and without Redis) #19467

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GiteaMirror · 2026-04-20T01:56:27-05:00

GiteaMirror commented

2026-04-20 01:56:27 -05:00

Originally created by @ashm-dev on GitHub (Feb 14, 2026).
Original GitHub issue: https://github.com/open-webui/open-webui/issues/21410

Description

The in-memory data structures SESSION_POOL, USAGE_POOL, and YdocManager._updates grow unboundedly, causing steady RAM increase that only resolves on restart.

This affects both modes:

Without Redis: data accumulates in Python process RAM
With Redis: data accumulates in Redis RAM, because RedisDict uses hset without expire — no TTL is ever set on keys. Storing data in Redis without TTL is problematic: it defeats Redis's ability to manage memory via eviction policies, and effectively turns Redis into an ever-growing store.

Root Causes

1. USAGE_POOL not cleaned on disconnect

File: backend/open_webui/socket/main.py

On disconnect, SESSION_POOL[sid] is deleted, but USAGE_POOL entries for that sid are only cleaned via periodic_usage_pool_cleanup() on timeout. If a socket closes without timing out first, entries persist indefinitely.

@sio.event
async def disconnect(sid):
    if sid in SESSION_POOL:
        del SESSION_POOL[sid]      # ← cleaned
        # USAGE_POOL[model_id][sid] ← NOT cleaned here

2. YdocManager._updates grows without bound

File: backend/open_webui/socket/utils.py

Every document edit appends to a list that is never evicted (neither in-memory nor in Redis):

async def append_to_updates(self, document_id, update):
    if not self._redis:
        if document_id not in self._updates:
            self._updates[document_id] = []
        self._updates[document_id].append(update)  # unbounded

With Redis, rpush is used without expire — same problem.

clear_document() is only called when all users leave a document. If at least one user stays connected, updates accumulate forever.

3. RedisDict stores data without TTL

File: backend/open_webui/socket/utils.py

RedisDict uses hset/hget with no expiration. SESSION_POOL, USAGE_POOL, and MODELS data persists in Redis indefinitely. This is undesirable — data in Redis should have TTL to allow proper memory management and prevent unbounded growth.

Observed Behavior

RAM usage grows steadily in small increments during normal usage
Only returns to baseline after full application restart
With Redis enabled, Python process memory stabilizes but Redis memory grows instead

Expected Behavior

USAGE_POOL entries for a sid should be removed on disconnect
YdocManager._updates should have a size limit or TTL
RedisDict should set TTL on keys (e.g. session data should expire after disconnect + grace period)
Redis keys for SESSION_POOL, USAGE_POOL should have reasonable expiration times

Originally created by @ashm-dev on GitHub (Feb 14, 2026). Original GitHub issue: https://github.com/open-webui/open-webui/issues/21410 ## Description The in-memory data structures `SESSION_POOL`, `USAGE_POOL`, and `YdocManager._updates` grow unboundedly, causing steady RAM increase that only resolves on restart. **This affects both modes:** - **Without Redis:** data accumulates in Python process RAM - **With Redis:** data accumulates in Redis RAM, because `RedisDict` uses `hset` without `expire` — no TTL is ever set on keys. Storing data in Redis without TTL is problematic: it defeats Redis's ability to manage memory via eviction policies, and effectively turns Redis into an ever-growing store. ## Root Causes ### 1. USAGE_POOL not cleaned on disconnect **File:** `backend/open_webui/socket/main.py` On disconnect, `SESSION_POOL[sid]` is deleted, but `USAGE_POOL` entries for that `sid` are only cleaned via `periodic_usage_pool_cleanup()` on timeout. If a socket closes without timing out first, entries persist indefinitely. ```python @sio.event async def disconnect(sid): if sid in SESSION_POOL: del SESSION_POOL[sid] # ← cleaned # USAGE_POOL[model_id][sid] ← NOT cleaned here ``` ### 2. YdocManager._updates grows without bound **File:** `backend/open_webui/socket/utils.py` Every document edit appends to a list that is never evicted (neither in-memory nor in Redis): ```python async def append_to_updates(self, document_id, update): if not self._redis: if document_id not in self._updates: self._updates[document_id] = [] self._updates[document_id].append(update) # unbounded ``` With Redis, `rpush` is used without `expire` — same problem. `clear_document()` is only called when all users leave a document. If at least one user stays connected, updates accumulate forever. ### 3. RedisDict stores data without TTL **File:** `backend/open_webui/socket/utils.py` `RedisDict` uses `hset`/`hget` with no expiration. `SESSION_POOL`, `USAGE_POOL`, and `MODELS` data persists in Redis indefinitely. This is undesirable — data in Redis should have TTL to allow proper memory management and prevent unbounded growth. ## Observed Behavior - RAM usage grows steadily in small increments during normal usage - Only returns to baseline after full application restart - With Redis enabled, Python process memory stabilizes but Redis memory grows instead ## Expected Behavior - `USAGE_POOL` entries for a `sid` should be removed on disconnect - `YdocManager._updates` should have a size limit or TTL - `RedisDict` should set TTL on keys (e.g. session data should expire after disconnect + grace period) - Redis keys for `SESSION_POOL`, `USAGE_POOL` should have reasonable expiration times

GiteaMirror closed this issue

2026-04-20 01:56:28 -05:00

GiteaMirror commented

2026-04-20 01:56:30 -05:00

@tjbck commented on GitHub (Feb 16, 2026):

Addressed in dev.

@tjbck commented on GitHub (Feb 16, 2026): Addressed in dev.

GiteaMirror referenced this issue

2026-04-25 08:24:40 -05:00

[GH-ISSUE #19467] feat: Left Side Panel custom width #34421

GiteaMirror referenced this issue

2026-05-05 21:06:29 -05:00