[IMP][POC] server: check signaling in parent process

[Xavier-Do]

When started with -d, registries are pre initialized before the workers
are spawned.
This means that the parent process will have some registries in memory
that will be available to the workers after the fork.
If the parent process never checks signaling and the sequence changes,
the copied registry will be reset at the first request.
This means that a new registry will be create after the fork everytime a
worker is recycled.
By checking the registry in the parent worker, we ensure that the forked
process will have a registry up to date (except if another change is
made during the fork...).

[robodoo]

Pull request status dashboard.

[Xavier-Do]

cc @odony

[rco-odoo]

For the record, this completely makes sense to me.
I suggest to test it in real-world conditions before merging.

[odony]

Makes the server die pretty quickly, after a few minutes max.

Judging by the semi-random errors, I'd say that we're sharing the db connections through multiple processes (after fork), therefore bypassing the ConnectionPool locks and corrupting the connection states.

Traceback (most recent call last):
  File "/code/odoo/service/server.py", line 929, in run
    self.check_registries()
  File "/code/odoo/service/server.py", line 833, in check_registries
    registry.check_signaling()
  File "/code/odoo/modules/registry.py", line 649, in check_signaling
    with closing(self.cursor()) as cr:
  File "/code/odoo/modules/registry.py", line 742, in cursor
    return self._db.cursor()
  File "/code/odoo/sql_db.py", line 760, in cursor
    return Cursor(self.__pool, self.dbname, self.dsn, serialized=serialized)
  File "/code/odoo/sql_db.py", line 300, in __init__
    self._cnx = pool.borrow(dsn)
  File "<decorator-gen-2>", line 2, in borrow
  File "/code/odoo/tools/func.py", line 69, in locked
    return func(inst, *args, **kwargs)
  File "/code/odoo/sql_db.py", line 682, in borrow
    cnx.reset()
psycopg2.errors.ActiveSqlTransaction: DISCARD ALL cannot run inside a transaction block

2022-05-18 13:56:13,131 3979454 WARNING db odoo.sql_db: Cursor not closed explicitly
Please enable sql debugging to trace the caller.
Exception ignored in: <function Cursor.__del__ at 0x7fa714ff9ee0>
Traceback (most recent call last):
  File "/code/odoo/sql_db.py", line 337, in __del__
    self._close(True)
  File "/code/odoo/sql_db.py", line 438, in _close
    if not self._obj:
  File "/code/odoo/sql_db.py", line 540, in __getattr__
    return getattr(self._obj, name)
  File "/code/odoo/sql_db.py", line 540, in __getattr__
    return getattr(self._obj, name)
  File "/code/odoo/sql_db.py", line 540, in __getattr__
    return getattr(self._obj, name)
  [Previous line repeated 989 more times]
RecursionError: maximum recursion depth exceeded

2022-05-18 14:13:14,289 3993576 ERROR db odoo.service.server: error with status PGRES_TUPLES_OK and no message from the libpq
Traceback (most recent call last):
  File "/code/odoo/service/server.py", line 929, in run
    self.check_registries()
  File "/code/odoo/service/server.py", line 833, in check_registries
    registry.check_signaling()  
  File "/code/odoo/modules/registry.py", line 650, in check_signaling
    cr.execute(""" SELECT base_registry_signaling.last_value,
  File "/code/odoo/sql_db.py", line 353, in execute
    res = self._obj.execute(query, params)
psycopg2.DatabaseError: error with status PGRES_TUPLES_OK and no message from the libpq
2022-05-18 14:13:14,292 3993576 INFO db odoo.service.server: Stopping forcefully

[Julien00859]

@Julien00859

[Julien00859]

@odony not so long ago you told me that we do not recycle http workers after x requests, can you confirm it?

[Xavier-Do]

Note that with https://github.com/odoo/odoo/compare/ae57ea9c54bc634543e554b6a5b3f965b52f9a49..ca1b6d2600ca4a3cb2833523d602a066035fb6ab the previous issue should be solved if it is still useful

[odony]

@odony not so long ago you told me that we do not recycle http workers after x requests, can you confirm it?

yes, we basically set the request limit very high in order to avoid recycling workers too often - if we don't have any reason to do so, it's just wasteful