I have found a workaround for this issue.
The root cause is probably something in the pyDal connector or psycopg2 or
threading. I leave the finding of that to the experts.
The workaround is to add code to gluon/scheduler.py to test the connection
before the rest of the Scheduler.send_heartbeat() function is executed.
If the connection-test fails, a new one is set up:
Insert this code at the top of the Scheduler.send_heartbeat() function
if self.db_thread:
# BKR 20180612 check if connection still works, if not -> throw away
self.db_thread and force reconnect
try:
x = self.db_thread(self.db_thread.scheduler_worker.worker_name ==
self.worker_name).select()
except self.db_thread._adapter.connection.OperationalError:
self.db_thread = None
With this addition, the scheduler works okay.
Op woensdag 6 juni 2018 21:26:40 UTC+2 schreef Bart:
>
> For a new application, i have installed web2py 2.16.1 under python 3.6 and
> using psycopg2 2.7.4 for postgresql access.
>
> Everything is working okay, except the web2py scheduler.
>
> After successfull execution of the first task, the scheduler gives an
> error in the send_heartbeat function.
> The task output is correctly stored in the database, with status
> COMPLETED. The transaction is committed.
>
> But then in the first heartbeat after completion, the error below is
> thrown:
>
> Looks like the database connection is lost unexpected.
>
> The strange thing is that this is only happening with psycopg2. When the
> PG8000 connector is used, everything is working fine.
> I have tested this on my development system (MacBook)
>
> On my production system under Ubuntu 16.04, the same thing is happening.
>
> Does anyone have a clue?
>
> The error:
>
> ERROR:web2py.scheduler.MyMac.local#21060:Error retrieving status
> Exception in thread Thread-30:
> Traceback (most recent call last):
> File "/Users/me/PycharmProjects/myapp/web2py/gluon/scheduler.py", line
> 1168, in send_heartbeat
> mybackedstatus = db(sw.worker_name ==
> self.worker_name).select().first()
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/objects.py",
>
> line 2250, in select
> return adapter.select(self.query, fields, attributes)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/base.py",
>
> line 762, in select
> return self._select_aux(sql, fields, attributes, colnames)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/base.py",
>
> line 718, in _select_aux
> rows = self._select_aux_execute(sql)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/base.py",
>
> line 712, in _select_aux_execute
> self.execute(sql)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/__init__.py",
>
> line 67, in wrap
> return f(*args, **kwargs)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/base.py",
>
> line 412, in execute
> rv = self.cursor.execute(command, *args[1:], **kwargs)
> psycopg2.OperationalError: server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
>
>
> During handling of the above exception, another exception occurred:
>
> Traceback (most recent call last):
> File
> "/usr/local/Cellar/python3/3.6.4_2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/threading.py",
>
> line 916, in _bootstrap_inner
> self.run()
> File "/Users/me/PycharmProjects/myapp/web2py/gluon/scheduler.py", line
> 637, in run
> self.send_heartbeat(counter)
> File "/Users/me/PycharmProjects/myapp/web2py/gluon/scheduler.py", line
> 1239, in send_heartbeat
> db.rollback()
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/base.py",
>
> line 704, in rollback
> self._adapter.rollback()
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/__init__.py",
>
> line 56, in wrap
> return f(*args, **kwargs)
> File
> "/Users/me/PycharmProjects/myapp/venv/lib/python3.6/site-packages/pydal/adapters/base.py",
>
> line 865, in rollback
> return self.connection.rollback()
> psycopg2.InterfaceError: connection already closed
>
--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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