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Re: pgAgent crashes on failed connection

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Dave Page <dpage(at)pgadmin(dot)org>, pgadmin-hackers <pgadmin-hackers(at)postgresql(dot)org>
Subject: Re: pgAgent crashes on failed connection
Date: 2011-09-28 19:37:06
Message-ID: CAHyXU0y+AycoMzuB4UV5Agt1edT2OVUSR4VTvggsQVSjFf29JA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgadmin-hackers
On Wed, Sep 28, 2011 at 3:32 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 28.09.2011 20:24, Merlin Moncure wrote:
>>
>> On Wed, Sep 28, 2011 at 2:16 PM, Heikki Linnakangas
>> <heikki(dot)linnakangas(at)enterprisedb(dot)com>  wrote:
>>>
>>> (sorry for the late reply, this fell through the cracks..)
>>>
>>> On 10.08.2011 11:48, Dave Page wrote:
>>>>
>>>> On Thu, Aug 4, 2011 at 8:30 PM, Merlin Moncure<mmoncure(at)gmail(dot)com>
>>>>  wrote:
>>>>>
>>>>> On Thu, Aug 4, 2011 at 2:19 PM, Heikki Linnakangas
>>>>> <heikki(dot)linnakangas(at)enterprisedb(dot)com>    wrote:
>>>>>>
>>>>>> I created 100 identical pgagent jobs, with one step that simply does
>>>>>> "SELECT
>>>>>> pg_sleep(10)". I then forced them all to run immediately, with "UPDATE
>>>>>> pgagent.pga_job SET jobnextrun=now();". pgagent crashed.
>>>>>>
>>>>>> What happened is that the when all those jobs are launched at the same
>>>>>> time,
>>>>>> the server ran into the max_connections limit, and pgagent didn't
>>>>>> handle
>>>>>> that too well. JobThread::JobThread constructor does not check for
>>>>>> NULL
>>>>>> result from DBConn::Get(), and passes a NULL connection to Job::Job,
>>>>>> which
>>>>>> tries to reference it, leading to a segfault.
>>>>>>
>>>>>> I propose the attached patch.
>>>>>
>>>>> hm, in the event that happens, is that logged in the client somehow?
>>>>> wouldn't you want to throw an exception or something like that?
>>>>
>>>> I think the most straightforward way to handle this is to dump an
>>>> error into pgagent.pga_joblog when deleting the thread. Might be a
>>>> little ugly to pass the original error message back rather than a
>>>> generic one though. Can you take a look Heikki?
>>>
>>> You mean something like the attached? Works for me, but inserting an
>>> entry
>>> in joblog for each failed attempt might create a lot of entries there, if
>>> the problem persists.
>>
>> Is it correct behavior to throw unhandled sql exception if the logging
>> query fails?
>
> Sorry, I didn't understand that. I don't see any exceptions been thrown.

whoop! never mind -- I assumed conn->Execute could throw an exception!

merlin

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