Re: Very frequent "Too many clients" eventually crashes postmaster

[Adrian Klaver <adrian.klaver@xxxxxxxxxxx>]

On 5/3/20 7:28 AM, Abraham, Danny wrote:
> Is there a way to eliminate postmaster crash/core ?
>
> A surge in short-term connections eventually crashes PG on  "no free slots in PMChildFlags array".
>
> Happens on AIX 7.2
>
> =>grep "2020-05-02 08:16" * | grep clients | wc -l
>         0
> =>grep "2020-05-02 08:17" * | grep clients | wc -l
>         0
> =>grep "2020-05-02 08:18" * | grep clients | wc -l
>       309
> =>grep "2020-05-02 08:19" * | grep clients | wc -l
>       603
> =>grep "2020-05-02 08:20" * | grep clients | wc -l
>       288
> =>grep "2020-05-02 08:21" * | grep clients | wc -l
>       230
>
> 2020-05-02 08:21:27.653 CDTFATAL:  no free slots in PMChildFlags array

Well:

backend/storage/ipc/pmsignal.c
/* Out of slots ... should never happen, else postmaster.c messed up */
        elog(FATAL, "no free slots in PMChildFlags array");
        return 0;                                       /* keep 
compiler quiet */


So:

1) What are your connection settings?

2) What is generating the client traffic?

3) Is there a pooler in front of the server?



--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx