open-webui/backend/open_webui/utils
Classic298 061f5e3a6d
perf: stop re-parsing the whole tool-argument buffer on every streamed chunk (#28858)
* perf: stop re-parsing the whole tool-argument buffer on every streamed chunk

Converting an OpenAI stream to Anthropic events buffers each tool call's arguments and, to find out when the JSON is complete, parsed the entire buffer again on every chunk. A tool call with large arguments pays that parse thousands of times, and the cost grows with the square of the argument size.

The parse now runs only when the buffer could actually be complete. A JSON object can only close on its final brace, so a chunk that does not end there cannot complete it. Arguments that are not an object, or that start with whitespace, keep parsing on every chunk exactly as before.

Measured on CPython 3.12 with 130 KB of tool arguments over 7648 chunks:

| | before | after |
|---|---|---|
| parses | 7648 | 1 |
| time | 382 ms | 0.82 ms |

The block closes on exactly the same chunk as before, verified by replaying randomized fragmentations of objects with braces inside strings, escaped characters, unicode escapes, arrays, bare scalars, leading and trailing whitespace and a buffer that never completes, against both JSON backends.

* refactor: read tool['arguments'] directly in the JSON completion guard

Restores the pre-existing comment above the guard to its original wording and drops the `buffered` local, so the guard and the parse call both read `tool['arguments']`, the name the rest of the file already uses for that buffer. Behaviour is unchanged: same three conditions in the same order, same short-circuit result.

* perf: strip whitespace in the tool-argument completion guard

The character guard only looked at the first and last byte of the buffer, so a
chunk that ended in a space still triggered a full parse and a tool argument
with leading whitespace fell back to parsing on every chunk. Stripping first
collapses both cases to a single parse at the end of the stream.

Measured on a streamed tool call, parses and wall time for the whole stream,
orjson on the left of the slash and stdlib json on the right:

| argument shape | before | after |
|---|---|---|
| 20 KB string, char-by-char deltas | 3678 parses, 56 / 28 ms | 1 parse, 3.1 / 3.1 ms |
| 200 KB, 20-char deltas | 1473 parses, 176 / 63 ms | 1 parse, 3.1 / 2.8 ms |
| 8 KB prose, leading whitespace | 715 parses, 5.5 / 2.5 ms | 1 parse, 0.18 ms |
| 8 KB of spaces inside a value | 713 parses, 6.0 / 2.9 ms | 1 parse, 0.83 / 0.72 ms |

The strip costs about 20 ns per delta on arguments that have no whitespace at
either end, which is where the old form was already optimal: a 20 KB compact
argument goes from 191 to 216 us over 1786 deltas. Soundness is unchanged, the
guard can still only skip a parse that would have failed: 2660892 buffers
(exhaustive to length 6 over a JSON-lexical alphabet, every prefix of 26 named
cases with a trailing byte appended, and every codepoint below U+3000 after a
complete document) with zero cases where a parse would have succeeded.
2026-08-31 01:18:05 -04:00
..
access_control fix: keep folder parent references acyclic (#28748) 2026-08-24 17:06:19 -04:00
images perf: build debug log messages lazily so disabled debug logs cost nothing (#27834) 2026-07-31 19:09:01 -05:00
mcp refac 2026-06-29 11:56:00 -05:00
telemetry refac(telemetry): drop deprecated semconv SpanAttributes subclass (#25784) 2026-06-29 02:05:34 -05:00
actions.py fix: enforce action availability and model access on the chat action route (#27243) 2026-07-23 12:23:05 -04:00
anthropic.py perf: stop re-parsing the whole tool-argument buffer on every streamed chunk (#28858) 2026-08-31 01:18:05 -04:00
asgi_middleware.py refac 2026-08-24 18:29:36 -04:00
ask_user.py fix: a rejected ask_user call ending the turn with no reply (#29252) 2026-08-31 00:17:21 -04:00
audit.py perf: build debug log messages lazily so disabled debug logs cost nothing (#27834) 2026-07-31 19:09:01 -05:00
auth.py fix: revoke existing sessions when a password changes (#28725) 2026-08-17 13:56:29 -07:00
automations.py refac 2026-08-31 01:06:15 -04:00
calendar.py refac 2026-08-29 16:14:32 -04:00
channels.py refac 2026-03-17 17:58:01 -05:00
chat.py perf: build info log messages lazily so raising the log level actually saves work (#27837) 2026-08-02 15:39:10 -05:00
chat_fork.py refac 2026-07-23 02:54:56 -04:00
chat_id.py refac 2026-07-26 21:12:14 -04:00
chat_variables.py perf: stabilize the model registry signature across workers (#29264) 2026-08-30 16:12:31 -04:00
code_interpreter.py refac 2026-07-31 17:41:14 -04:00
context_compaction.py refac 2026-08-23 13:36:53 -04:00
embeddings.py refac: modernize type annotations (PEP 604 / PEP 585) 2026-05-12 17:10:15 +09:00
files.py refac 2026-08-31 00:11:13 -04:00
filter.py refac 2026-08-30 21:47:28 -04:00
groups.py refac: modernize type annotations (PEP 604 / PEP 585) 2026-05-12 17:10:15 +09:00
headers.py refac 2026-08-24 18:38:29 -04:00
json_codec.py perf: write task payloads to Redis as bytes (#28833) 2026-08-20 12:58:52 -07:00
json_response.py perf: optional orjson JSON codec behind ENABLE_ORJSON (#27583) 2026-07-27 03:45:37 -04:00
logger.py perf: stop formatting every exported log record twice under OTEL log export (#27840) 2026-08-10 23:13:52 -06:00
memory.py refac 2026-08-10 19:28:21 -06:00
middleware.py perf: skip the tool approval drain lookup for fresh chat messages (#29142) 2026-08-30 23:57:11 -05:00
misc.py refac 2026-08-31 00:39:16 -04:00
model_ids.py refac 2026-07-26 23:09:22 -04:00
models.py refac 2026-08-31 00:53:55 -04:00
notifications.py refac 2026-07-27 19:39:36 -04:00
oauth.py chore: format 2026-08-25 16:53:53 -04:00
payload.py refac 2026-08-16 22:56:19 -07:00
pdf_generator.py refac: modernize type annotations (PEP 604 / PEP 585) 2026-05-12 17:10:15 +09:00
plugin.py perf: build info log messages lazily so raising the log level actually saves work (#27837) 2026-08-02 15:39:10 -05:00
rate_limit.py refac: modernize type annotations (PEP 604 / PEP 585) 2026-05-12 17:10:15 +09:00
redis.py fix: Set default Redis socket timeout to None (#27104) 2026-07-27 00:30:00 -04:00
response.py refac 2026-08-17 00:57:57 -07:00
sanitize.py refac 2026-03-17 17:58:01 -05:00
security_headers.py refac 2026-08-24 18:29:36 -04:00
session_pool.py fix: long streamed lines no longer abort the response (#28114) 2026-08-25 12:16:37 -04:00
subagents.py chore: format 2026-08-25 16:53:53 -04:00
task.py refac 2026-06-19 00:16:06 +02:00
terminals.py refac 2026-08-19 22:48:32 -07:00
timers.py fix: index the chat queries that make large SQLite instances unusable (#27663) 2026-08-23 16:11:54 -05:00
tool_approval.py chore: format 2026-08-25 16:53:53 -04:00
tools.py refac 2026-08-31 00:05:34 -04:00
validate.py refac 2026-07-27 19:39:36 -04:00
valves.py refac 2026-07-31 17:41:14 -04:00
webhook.py perf: build debug log messages lazily so disabled debug logs cost nothing (#27834) 2026-07-31 19:09:01 -05:00