Unportable use of select for timeouts in PostgresNode.pm

I've been trying to get to the bottom of a nasty hang in buildfarm
member jacana when running the pg_ctl TAP test. This test used to work,
and was last known to work on June 22nd.

My attention has become focussed on this change in commit de3de0afd:

- # Wait a second before retrying.
- sleep 1;
+ # Wait 0.1 second before retrying.
+ select undef, undef, undef, 0.1;

This is a usage that is known not to work in Windows - IIRC we
eliminated such calls from our C programs at the time of the Windows
port - and it seems to me very likely to be the cause of the hang.
Instead I think we should use the usleep() function from the standard
(from 5.8) Perl module Time::HiRes, as recommended in the Perl docs for
the sleep() function for situations where you need finer grained
timeouts. I have verified that this works on jacana and friends.

Unless I hear objections I'll prepare a patch along those lines.

cheers

andrew

--
Andrew Dunstan https://www.2ndQuadrant.com
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