error: cannot switch to a different thread

[Alvin Ang]

Deployed web2py to production lately, keep getting an intermittent error "error: cannot switch to a different thread". Please help.

• CentOS Linux release 7.4.1708
  
• web2py Version 2.16.1-stable+timestamp.2017.11.14.05.54.25
  
• Apache Version 2.4.33
• MySQL Version 10.1.30-MariaDB
• Python Version 2.7.15

Traceback (most recent call last):

  File "/home/wesl/web2py/gluon/restricted.py", line 219, in restricted

    exec(ccode, environment)

  File "/home/wesl/web2py/applications/wesl/controllers/default.py", line 290, in <module>

  File "/home/wesl/web2py/gluon/globals.py", line 419, in <lambda>

    self._caller = lambda f: f()

  File "/home/wesl/web2py/applications/wesl/controllers/default.py", line 50, in index

    row = db(db.team).select()

  File "/home/wesl/web2py/gluon/packages/dal/pydal/objects.py", line 2250, in select

    return adapter.select(self.query, fields, attributes)

  File "/home/wesl/web2py/gluon/packages/dal/pydal/adapters/base.py", line 762, in select

    return self._select_aux(sql, fields, attributes, colnames)

  File "/home/wesl/web2py/gluon/packages/dal/pydal/adapters/base.py", line 718, in _select_aux

    rows = self._select_aux_execute(sql)

  File "/home/wesl/web2py/gluon/packages/dal/pydal/adapters/base.py", line 712, in _select_aux_execute

    self.execute(sql)

  File "/home/wesl/web2py/gluon/packages/dal/pydal/adapters/__init__.py", line 67, in wrap

    return f(*args, **kwargs)

  File "/home/wesl/web2py/gluon/packages/dal/pydal/adapters/base.py", line 412, in execute

    rv = self.cursor.execute(command, *args[1:], **kwargs)

  File "/home/wesl/web2py/gluon/contrib/pymysql/cursors.py", line 166, in execute

    result = self._query(query)

  File "/home/wesl/web2py/gluon/contrib/pymysql/cursors.py", line 322, in _query

    conn.query(q)

  File "/home/wesl/web2py/gluon/contrib/pymysql/connections.py", line 835, in query

    self._affected_rows = self._read_query_result(unbuffered=unbuffered)

  File "/home/wesl/web2py/gluon/contrib/pymysql/connections.py", line 1019, in _read_query_result

    result.read()

  File "/home/wesl/web2py/gluon/contrib/pymysql/connections.py", line 1302, in read

    first_packet = self.connection._read_packet()

  File "/home/wesl/web2py/gluon/contrib/pymysql/connections.py", line 961, in _read_packet

    packet_header = self._read_bytes(4)

  File "/home/wesl/web2py/gluon/contrib/pymysql/connections.py", line 988, in _read_bytes

    data = self._rfile.read(num_bytes)

  File "/home/wesl/web2py/gluon/contrib/pymysql/_socketio.py", line 59, in readinto

    return self._sock.recv_into(b)

  File "/home/wesl/lib/python2.7/site-packages/gevent/_socket2.py", line 330, in recv_into

    self._wait(self._read_event)

  File "src/gevent/_hub_primitives.py", line 265, in gevent.__hub_primitives.wait_on_socket

  File "src/gevent/_hub_primitives.py", line 266, in gevent.__hub_primitives.wait_on_socket

  File "src/gevent/_hub_primitives.py", line 252, in gevent.__hub_primitives._primitive_wait

  File "src/gevent/_hub_primitives.py", line 46, in gevent.__hub_primitives.WaitOperationsGreenlet.wait

  File "src/gevent/_hub_primitives.py", line 46, in gevent.__hub_primitives.WaitOperationsGreenlet.wait

  File "src/gevent/_hub_primitives.py", line 55, in gevent.__hub_primitives.WaitOperationsGreenlet.wait

  File "src/gevent/_waiter.py", line 151, in gevent.__waiter.Waiter.get

  File "src/gevent/_greenlet_primitives.py", line 59, in gevent.__greenlet_primitives.SwitchOutGreenletWithLoop.switch

  File "src/gevent/_greenlet_primitives.py", line 59, in gevent.__greenlet_primitives.SwitchOutGreenletWithLoop.switch

  File "src/gevent/_greenlet_primitives.py", line 63, in gevent.__greenlet_primitives.SwitchOutGreenletWithLoop.switch

  File "src/gevent/__greenlet_primitives.pxd", line 35, in gevent.__greenlet_primitives._greenlet_switch

error: cannot switch to a different thread

[黄祥]

seems it's related with gevent

ref:

https://github.com/miguelgrinberg/Flask-SocketIO/issues/65

did you use apache as a reverse proxy and gevent as a web server?

best regards,

stifan

[Alvin Ang]

Not really, I'm using Apache as web server.

Best Regards,

Alvin

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[Alvin Ang]

seems like it's due to my Scheduler implementation within the App, I remove scheduler.py from models and App starts to work fine.

best regards,

Alvin