Re: [HACKERS] Why does logical replication launcher exit with exitcode 1?

On 02/08/17 11:03, Andres Freund wrote:
> Hi,
>
> On 2017-08-02 10:58:32 +1200, Thomas Munro wrote:
>> When I shut down a cluster that isn't using logical replication, it
>> always logs a line like the following.  So do the build farm members I
>> looked at.  I didn't see anything about this in the open items list --
>> isn't it a bug?
>>
>> 2017-08-02 10:39:25.007 NZST [34781] LOG:  worker process: logical
>> replication launcher (PID 34788) exited with exit code 1
> Exit code 0 signals that a worker should be restarted. Therefore
> graceful exit can't really use that.  I think a) we really need to
> improve bgworker infrastructure around that b) shows the limit of using
> bgworkers for this kinda thing - we should probably have a more bgworker
> like infrastructure for internal workers.
>
> - Andres
>
>
Returning zero to indicate success is a holdover to the time computers 
could only run one program at a time.  At the end of the code there was 
a jump table of 4 byte entries.  The first entry with a displacement of 
zero was the location to jump to for a normal exit, subsequent entries 
where for various error conditions.  This why often return codes where 
in positive multiples of 4, since we don't use jump tables now - more & 
more people are using any integers they want.

So apart from convention, returning zero is no longer held to be a 
sacred to indicate something exited okay.  In fact since, zero could 
simply mean a value was not explicitly assigned, hence it is actually a 
very dangerous value  to be used to indicate success!


Cheers,
Gavin