Since v0.11.0 shipped aiodns, aiohttp silently switched every outbound request from the OS resolver to c-ares. On some Windows hosts the bundled c-ares 1.34.6 (pycares 5) discovers only 127.0.0.1:53 as nameserver, so every external provider lookup fails (#28013). In Docker the long-lived c-ares channel intermittently stops resolving container names while Docker's embedded DNS keeps answering, which wipes the Ollama model list and fails all in-flight chats with a misleading "Model not found" (#28215).
This restores the pre-0.11 ThreadedResolver (OS resolver) by default and gates the c-ares path behind a new env var, AIOHTTP_CLIENT_ASYNC_DNS_RESOLVER, off by default. The event-loop DNS perf improvement is now opt-in for deployments whose resolver setup is known to work with c-ares, instead of a process-wide side effect of the package being installed.
aiodns is also downgraded and pinned to 3.6.1 (pycares<5), the last release before the broken c-ares 1.34.6 build, so opting in does not hit the Windows regression. The hardcoded AsyncResolver in the Mistral OCR loader now follows the same switch. Simply removing aiodns instead was not an option because opting in would then be impossible, and #28215 showed the Docker failure is c-ares itself, not aiodns 4.x.
Raising GLOBAL_LOG_LEVEL to WARNING buys quieter output but not less work: 241 INFO call sites interpolate their payload into an f-string before the logging call gets to drop it. The heaviest is get_doc, which logs every chunk id and metadata dict in a collection, so on the full-context retrieval path that is the entire knowledge base, once per chat request.
That one line at WARNING, CPython 3.12:
| knowledge base | payload | before | after |
| -------------- | ------- | -------- | ------- |
| top-k of 3 | 1.2 kB | 3.8 us | 0.07 us |
| 500 chunks | 201 kB | 583.6 us | 0.08 us |
| 5000 chunks | 2.0 MB | 5.8 ms | 0.15 us |
The lazy form log.info('query_doc:result %s %s', result.ids, result.metadatas) hands the payload to record.getMessage(), which the InterceptHandler only reaches once a record has passed the level check. Output at INFO is byte-identical. Two sites that already built their message eagerly, one str concat and one % operator, move to the same lazy form.
GLOBAL_LOG_LEVEL defaults to INFO, so every log.debug(...) in the backend is discarded, but the message is built first: 187 call sites interpolate their payload into an f-string before the logging call runs, so the work happens on every request and the result is thrown away. The worst one sits in process_chat_payload and stringifies the whole request body, full conversation history included, once per chat completion.
That one line with DEBUG disabled, CPython 3.12:
| conversation | payload | before | after |
| ------------ | ------- | -------- | ------- |
| 4 messages | 1.2 kB | 3.4 us | 0.07 us |
| 20 messages | 17 kB | 24.8 us | 0.07 us |
| 60 messages | 123 kB | 216.6 us | 0.07 us |
The lazy form log.debug('form_data: %s', form_data) hands the payload to record.getMessage(), which the InterceptHandler only reaches once a record has passed the level check. With DEBUG enabled the emitted lines are byte-identical, f'{x=}' sites included: those map to %r. MistralLoader._debug_log callers get the same treatment, since that wrapper already forwards *args.
Mirrors the ENABLE_FORWARD_USER_INFO_HEADERS pattern already used by
the audio/TTS and external document loader integrations, so the
Mistral OCR backend can identify the requesting user the same way.
Co-authored-by: andrep <vpham@aut.ac.nz>
_upload_file_async built its multipart body with
`aiohttp.streams.FilePayload(...)`, which no longer exists in aiohttp
(payload classes live in aiohttp.payload, and there is no FilePayload).
The reference sits inside a lazy closure, so import succeeds and only the
async Mistral OCR file-upload path blows up at runtime with
AttributeError on every call.
Mirror the working sync path: open the file in a context manager and let
MultipartWriter.append(file_obj, {...}) build a streaming
BufferedReaderPayload, with the POST issued inside the open() block so
the handle stays valid for the whole upload. Preserves the streaming /
memory-efficiency intent.
Found via the dependency-contract test suite (unit/deps/test_aiohttp.py),
which pins aiohttp.streams.FilePayload as absent.
Classic298