the POV of this question is wrong. Scheduler processes do what you ask them
to do, without nothing else added.
The same thing you observe would happen if you try to execute your tasks
manually. It just seems that what you are asking them to do violates your
model (i.e. either you had already a row with fa=something in the table OR
you asked more than one task to insert fa=something in the table, which
would, at the 2nd run, fail as expected)
On Wednesday, September 28, 2016 at 10:13:10 PM UTC+2, Dave S wrote:
>
>
>
> On Wednesday, September 28, 2016 at 3:58:10 AM UTC-7, Pierre wrote:
>>
>> Hi ,
>>
>>
>> I noticed an unexpected behaviour when running two scheduler processes.
>>
>>
>> The situation is this :
>>
>>
>> A db with a table like :
>>
>>
>> db.define_table('taba',
>> Field('fa', unique=True, requires = IS_NOT_IN_DB(db,'taba.fa')),
>> Field('fb'))
>>
>>
>>
>> a task (same function different args) distributed to the processes which
>> contains a :
>>
>>
>> ret = db.taba.validate_and_insert(fa='something', fb='somethingelse')
>>
>>
>> this generates an exception like so :
>>
>>
>> File "/opt/web2py/gluon/packages/dal/pydal/objects.py", line 737, in
>> validate_and_insert
>> response.id = self.insert(**new_fields)
>> File "/opt/web2py/gluon/packages/dal/pydal/objects.py", line 712, in
>> insert
>> ret = self._db._adapter.insert(self, self._listify(fields))
>> File "/opt/web2py/gluon/packages/dal/pydal/adapters/base.py", line 739,
>> in insert
>>
>> raise e
>> IntegrityError: duplicate key value violates unique constraint
>> "taba_fa_key"
>>
>> DETAIL: Key (fa)=(something) already exists.
>>
>>
>>
>> and task fails
>>
>>
>> This doesn't happen when running a single scheduler process so I guess
>> the two scheduler processes collide(….they try to write the same value to
>> the db at the same time……)
>>
>>
>> how do I fix this ? Why can't the two processes cooperate ? Am I limited
>> to running a single sched process ?
>>
>
> What do you mean by 2 sched processes? Are you calling
> schedule=Scheduler(db, migrate=False)
> twice? I don't think you're supposed to do that.
>
> There can be a variable number of workers, and ISTR that the default is 4.
>
> If you aren't instantiating twice, then the next question is how are you
> queuing your tasks? Are you queuing tasks from a controller? From a
> script?
>
> /dps
>
>
>
>
>
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