Re: Improving the isolationtester: fewer failures, less delay

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Improving the isolationtester: fewer failures, less delay
Date: 2021-06-15 19:23:53
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On 6/14/21 10:57 PM, Tom Lane wrote:
> This is a followup to the conversation at [1], in which we speculated
> about constraining the isolationtester's behavior by annotating the
> specfiles, in order to eliminate common buildfarm failures such as [2]
> and reduce the need to use long delays to stabilize the test results.
> I've spent a couple days hacking on this idea, and I think it has worked
> out really well. On my machine, the time needed for "make installcheck"
> in src/test/isolation drops from ~93 seconds to ~26 seconds, as a result
> of removing all the multiple-second delays we used before. Also,
> while I'm not fool enough to claim that this will reduce the rate of
> bogus failures to zero, I do think it addresses all the repeating
> failures we've seen lately.
> In the credit-where-credit-is-due department, this owes some inspiration
> to the patch Asim Praveen offered at [3], though this takes the idea a
> good bit further.
> This is still WIP to some extent, as I've not spent much time looking at
> specfiles other than the ones with big delays; there may be additional
> improvements possible in some places. Also, I've not worried about
> whether the tests pass in serializable mode, since we have problems there
> already [4]. But this seemed like a good point at which to solicit
> feedback and see what the cfbot thinks of it.

Cool stuff. Minor gripe while we're on $subject - I wish we'd rename it.
It's long outgrown the original purpose that gave it its name, and
keeping the name makes it unnecessarily obscure. Yes, I know Lisp still
has car and cdr, but we don't need to follow that example.



Andrew Dunstan

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