invalid HTTP request received

本番環境でfastapiを動かしている時に以下のエラーが出力されました。

INFO:     Started server process [9806]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
WARNING:  Invalid HTTP request received.
Traceback (most recent call last):
  File "/home/ec2-user/.local/lib/python3.7/site-packages/uvicorn/protocols/http/h11_impl.py", line 170, in handle_events
    event = self.conn.next_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 443, in next_event
    exc._reraise_as_remote_protocol_error()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_util.py", line 76, in _reraise_as_remote_protocol_error
    raise self
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 425, in next_event
    event = self._extract_next_receive_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 367, in _extract_next_receive_event
    event = self._reader(self._receive_buffer)
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_readers.py", line 73, in maybe_read_from_IDLE_client
    request_line_re, lines[0], "illegal request line: {!r}", lines[0]
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_util.py", line 88, in validate
    raise LocalProtocolError(msg)
h11._util.RemoteProtocolError: illegal request line: bytearray(b'\x16\x03\x01\x02\x00\x01\x00\x01\xfc\x03\x03\x91\xa5\xe2Y\xf0\xa1\xdd\x1d+\x08\x1c\r\x15X\x1d@\x1e/\xb1N\x00\xb5\xe5\xec\xf3F\x1fm\x03\xa1{> \xa80\xb4\x14\x1aUs\xaa\xcd\xc3<s\xcd\xd1\x17\xdf3\x0e\xdbh\xd1c\x88}\x8c\x1f\xa5\x15\x9aa\x14I\x00 ')
WARNING:  Invalid HTTP request received.
Traceback (most recent call last):
  File "/home/ec2-user/.local/lib/python3.7/site-packages/uvicorn/protocols/http/h11_impl.py", line 170, in handle_events
    event = self.conn.next_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 443, in next_event
    exc._reraise_as_remote_protocol_error()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_util.py", line 76, in _reraise_as_remote_protocol_error
    raise self
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 425, in next_event
    event = self._extract_next_receive_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 367, in _extract_next_receive_event
    event = self._reader(self._receive_buffer)
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_readers.py", line 68, in maybe_read_from_IDLE_client
    raise LocalProtocolError("illegal request line")
h11._util.RemoteProtocolError: illegal request line
WARNING:  Invalid HTTP request received.
Traceback (most recent call last):
  File "/home/ec2-user/.local/lib/python3.7/site-packages/uvicorn/protocols/http/h11_impl.py", line 170, in handle_events
    event = self.conn.next_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 443, in next_event
    exc._reraise_as_remote_protocol_error()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_util.py", line 76, in _reraise_as_remote_protocol_error
    raise self
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 425, in next_event
    event = self._extract_next_receive_event()
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_connection.py", line 367, in _extract_next_receive_event
    event = self._reader(self._receive_buffer)
  File "/home/ec2-user/.local/lib/python3.7/site-packages/h11/_readers.py", line 68, in maybe_read_from_IDLE_client
    raise LocalProtocolError("illegal request line")
h11._util.RemoteProtocolError: illegal request line
WARNING:  Invalid HTTP request received.

とてもログを見ることが出来ないので原因をすることにしました。

原因はuvicornのバージョンにあった

uvicorn #344で議論されているように、uvicornとnginxの組み合わせには散発的なエラーがあります。この問題の原因究明のため uvicorn version 0.13.2からエラーの詳細がログに出力される様になりました。2022年3月22日現在、この問題と、エラーログの出力は続いているようです。

解決策

応急処置ではありますが、uvicornのversionを0.13.1にダウングレードしましょう。