Re: TRAP: FailedAssertion("!(TransactionIdPrecedesOrEquals

On 2017-12-19 23:35, Erik Rijkers wrote:
> I saw this just now:
> 
> TRAP: FailedAssertion("!(TransactionIdPrecedesOrEquals(safeXid,
> snap->xmin))", File: "snapbuild.c", Line: 580)
> 
> while running 50 cascading instances on a single machine.

Sorry, that was probably too terse, I should explain that a little.

After initing 50 instances, I set up and run a pgbench session in the 
master session; the pgbench lines are:

   init: pgbench --port=6515 --quiet --initialize --scale=1 postgres
   run:  pgbench -M prepared -c 16 -j 8 -T 1 -P 1 -n postgres -- scale 1

the other instances then catch up.  The whole takes 5 minutes or so

I vary scale, duration, and number of instances.  I haven't had it fail 
in this way yet but I mostly tried with lower number of instances (up to 
25 or so).

> select version():
> PostgreSQL 11devel_HEAD_20171219_2158_7d3583ad9ae5 on
> x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18) 6.3.0 20170516,
> 64-bit
> 
> 
> I don't know if the admittedly somewhat crazy 50 instances make that
> error acceptable/expected but I thought I'd report it anyway.
> 
> thanks,
> 
> Erik Rijkers