aio-libs/aiohttp · error · ContentLengthError

Not enough data to satisfy content length header (received {

Error message

Not enough data to satisfy content length header (received {received} of {expected} bytes).

What it means

ContentLengthError raised in HttpPayloadParser.feed_eof when the connection closes while the body is being read in PARSE_LENGTH mode and fewer than Content-Length bytes arrived. The message reports received vs expected bytes.

Source

Thrown at aiohttp/http_parser.py:918

        self.payload = real_payload

    def pause_reading(self) -> None:
        self._paused = True

    def feed_eof(self) -> None:
        if self._type == ParseState.PARSE_UNTIL_EOF:
            self._eof_pending = True
            while self._more_data_available:
                if self._paused:
                    self._paused = False
                    return  # Will resume via feed_data(b"") later
                self._more_data_available = self.payload.feed_data(b"")
            self.payload.feed_eof()
            self.done = True
            self._eof_pending = False
        elif self._type == ParseState.PARSE_LENGTH:
            received = self._length_expected - self._length
            raise ContentLengthError(
                f"Not enough data to satisfy content length header "
                f"(received {received} of {self._length_expected} bytes)."
            )
        elif self._type == ParseState.PARSE_CHUNKED:
            raise TransferEncodingError(
                "Not enough data to satisfy transfer length header."
            )

    def feed_data(
        self, chunk: bytes, SEP: _SEP = b"\r\n", CHUNK_EXT: bytes = b";"
    ) -> tuple[PayloadState, bytes]:
        """Receive a chunk of data to process.

        Return:
            PayloadState - The current state of payload processing.
                           This function may be called with empty bytes after returning
                           PAYLOAD_HAS_PENDING_INPUT to continue processing after a pause.
            bytes - If payload is complete, this is the unconsumed bytes intended for the

View on GitHub (pinned to c0ef574e29)

Solutions

1. Verify the server's Content-Length matches the actual body size (capture with curl -i).
2. Check for proxies/CDNs truncating large responses or applying compression that changes body size.
3. Retry the request; if reproducible, report to the server owner.
4. Handle ContentLengthError and fall back to a streaming/transfer-encoding read.

from aiohttp.http_exceptions import ContentLengthError
try:
    body = await resp.read()
except ContentLengthError:
    # truncated body — retry or stream
    ...

When it happens

Trigger: Server declared Content-Length: N but the socket closed after delivering < N bytes. feed_eof() in the PARSE_LENGTH branch computes `received = _length_expected - _length` and raises ContentLengthError.

Common situations: Truncated responses from a reverse proxy that times out mid-body; upstream connection drop; Content-Length computed wrong (head vs body mismatch); keep-alive closed early; compression applied without recomputing Content-Length.

Related errors

• Not enough data to satisfy transfer length header.
• chunked can not be set if Content-Length header is set
• Got more than {limit} bytes when reading: {line!r}.
• Duplicate '{name}' header found.
• Data after `Connection: close`

AI-assisted analysis of aio-libs/aiohttp@c0ef574e29 (2026-08-04). Data as JSON: /data/errors/4680424f6f4596ba.json. Report an issue: GitHub.