Re: [Postgres-xc-developers] GTM standby issue: Cannot assign the transaction, already in use

[Koichi S. <koi...@gm...>]

I've got the issue.   Yes, this is what I was concerning about and I
appreciate for finding the issue and possible cause.

How much you're in a hurry?   I'm now in Chicago for Postgres Open and
might not have a time to look into it until I finish my presentation
tomorrow.

Regards;

---
Koichi Suzuki


2013/9/16 Nikhil Sontakke <ni...@st...>

> Hi,
>
> One of our customers reported the following issue on the Standby:
>
> 1:140638715778816:2013-09-13 07:08:11.351 EDT -ERROR:  GTM_TransactionInfo
> already in use.  Cannot assign the transaction: handle (3745).
>
> I investigated this and thought I had fixed this with the patch that I
> have provided on the thread with $SUBJECT (Issues with GTM Standby Syncup)
>
> That patch reduced the number of these messages, but yet, some still found
> their way into the Standby logs.
>
> What's happening is that GTM Standby as part of the initial syncup with
> the GTM, sends gtm_standby_end_backup() after which the main GTM activates
> all the threads which had been paused earlier for the syncup.
>
> In the time between Standby calls the above function and actually starts
> listening for incoming data, some packets from the GTM are lost. Remember
> this will be the case when the GTM is already very highly loaded and lots
> of threads are running.
>
> If these packets contain commit info for those GXIDs that were added in
> the initial syncup, then they are lost and as a result these slots do not
> get cleaned up at the standby causing the above error messages.
>
> I think the best fix would be to delay and send gtm_standby_end_backup()
> inside the Serverloop, JUST before the Standby is going to do the select()
> call. Am trying a patch on similar lines but getting some issues, will get
> back with a patch soon.
>
> Regards,
> Nikhils
> --
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