Re: [HACKERS] Proposal : For Auto-Prewarm.

On Tue, Feb 7, 2017 at 5:14 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
> On Tue, Feb 7, 2017 at 12:24 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> On Tue, Feb 7, 2017 at 11:53 AM, Beena Emerson <memissemerson@gmail.com> wrote:
>>> Are 2 workers required?
>>>
>>
>> I think in the new design there is a provision of launching the worker
>> dynamically to dump the buffers, so there seems to be a need of
>> separate workers for loading and dumping the buffers.  However, there
>> is no explanation in the patch or otherwise when and why this needs a
>> pair of workers.  Also, if the dump interval is greater than zero,
>> then do we really need to separately register a dynamic worker?
>
> We have introduced a new value  -1 for pg_prewarm.dump_interval this
> means we will not dump at all, At this state, I thought auto
> pg_prewarm process need not run at all, so I coded to exit the auto
> pg_prewarm immediately. But If the user decides to start the auto
> pg_prewarm to dump only without restarting the server, I have
> introduced a launcher function "launch_pg_prewarm_dump" to restart the
> auto pg_prewarm only to dump. Since now we can launch worker only to
> dump, I thought we can redistribute the code between two workers, one
> which only does prewarm (load only) and another dumps periodically.
> This helped me to modularize and reuse the code. So once load worker
> has finished its job, it registers a dump worker and then exists.
> But if max_worker_processes is not enough to launch the "auto
> pg_prewarm dump" bgworker
> We throw an error
> 2017-02-07 14:51:59.789 IST [50481] ERROR:  registering dynamic
> bgworker "auto pg_prewarm dump" failed c
> 2017-02-07 14:51:59.789 IST [50481] HINT:  Consider increasing
> configuration parameter "max_worker_processes".
>
> Now thinking again instead of such error and then correcting same by
> explicitly launching the auto pg_prewarm dump bgwroker through
> launch_pg_prewarm_dump(), I can go back to original design where there
> will be one worker which loads and then dumps periodically. And
> launch_pg_prewarm_dump will relaunch dump only activity of that
> worker. Does this sound good?
>

Won't it be simple if you consider -1 as a value to just load library?
 For *_interval = -1, it will neither load nor dump.