Re: DB Server slow down & hang during Peak hours of Usage

On Tue, Aug 8, 2023 at 5:49 PM Marc Millas <marc(dot)millas(at)mokadb(dot)com> wrote:

> also,
> checkpoint setup are all default values
>
> you may try to
> checkpoint_completion_target = 0.9
> checkpoint_timeout = 15min
> max_wal_size = 5GB
>
> and, as said in the previous mail, check the checkpoint logs
>
> Also, all vacuum and autovacuum values are defaults
> so, as autovacuum_work_mem = -1
> the autovacuum processes will use the 4 GB setuped by maintenance_work_mem
> = 4096MB
> as there are 3 launched at the same time, its 12 GB "eaten"
> which doesn't look like a good idea, so set
> autovacuum_work_mem = 128MB
>
> also pls read the autovacuum doc for your version (which is ?) here for
> postgres 12:
> https://www.postgresql.org/docs/12/runtime-config-autovacuum.html
>
>
>
> Marc MILLAS
> Senior Architect
> +33607850334
> www.mokadb.com
>
>
>
> On Tue, Aug 8, 2023 at 1:59 PM Marc Millas <marc(dot)millas(at)mokadb(dot)com> wrote:
>
>> Hello,
>> in the postgresql.conf joined, 2 things (at least) look strange:
>> 1) the values for background writer are the default values, fit for a
>> server with a limited writes throughput.
>> you may want to increase those, like:
>> bgwriter_delay = 50ms
>> bgwriter_lru_maxpages = 400
>> bgwriter_lru_multiplier = 4.0
>> and check the checkpoint log to see if there are still backend processes
>> writes.
>>
>> 2) work_mem is set to 2 GB.
>> so, if 50 simultaneous requests use at least one buffer for sorting,
>> joining, ..., you will consume 100 GB of RAM
>> this value seems huge for the kind of config/usage you describe.
>> You may try to set work_mem to 100 MB and check what's happening.
>>
>> Also check the logs, postgres tells his life there...
>>
>>
>>
>>
>>
>> Marc MILLAS
>> Senior Architect
>> +33607850334
>> www.mokadb.com
>>
>>
>>
Thank you all for your time and the valuable inputs to fix the issue. Let
me tune conf parameters as advised and will get back with the results and
log outputs .

Krishane

>
>> On Mon, Aug 7, 2023 at 3:36 PM KK CHN <kkchn(dot)in(at)gmail(dot)com> wrote:
>>
>>> List ,
>>>
>>> *Description:*
>>>
>>> Maintaining a DB Server Postgres and with a lot of read writes to this
>>> Server( virtual machine running on ESXi 7 with CentOS 7) .
>>>
>>> ( I am not sure how to get the read / write counts or required IOPS or
>>> any other parameters for you. If you point our I can execute those
>>> commands and get the data. )
>>>
>>> Peak hours say 19:00 Hrs to 21:00 hrs it hangs ( The application is an
>>> Emergency call response system writing many Emergency Response vehicles
>>> locations coordinates to the DB every 30 Seconds and every emergency call
>>> metadata (username, phone number, location info and address of the caller
>>> to the DB for each call)
>>>
>>> During these hours the system hangs and the Application ( which shows
>>> the location of the vehicles on a GIS map hangs ) and the CAD machines
>>> which connects to the system hangs as those machines can't connect to the
>>> DB and get data for displaying the caller information to the call taking
>>> persons working on them. )
>>>
>>> *Issue : *
>>> How to trace out what makes this DB hangs and make it slow and how to
>>> fix it..
>>>
>>> *Resource poured on the system :*
>>>
>>> *64 vCPUs allocate ( Out of a host machine comprised of 2 processor
>>> slots of 20 cores each with Hyper Threading, intel xeon 2nd Gen, CPU usage
>>> show 50 % in vCentre Console), and RAM 64 GB allocated ( buy usage always
>>> showing around 33 GB only ) *
>>>
>>> *Query :*
>>>
>>> How to rectify the issues that makes the DB server underperforming and
>>> find a permanent fix for this slow down issue*. *
>>>
>>> *Attached the Postgres.conf file here for reference .*
>>>
>>> *Any more information required I can share for analysis to fix the
>>> issue. *
>>>
>>>
>>> *Krishane *
>>>
>>