Add check_replication_slots check to check the delay on any replication slots.

[glynastill]

"Delay" is measured as size of transaction logs retained for the slot e.g:
check_postgres_replication_slots -db=TEST -H=192.168.0.106 -warning=32M -critical=64M

[df7cb]

Hi,

thanks for the pull request! Some comments:

• this needs a testcase. I'll paste below what I got when I tried this action, but there's some bits to resolve first
• it just doesn't work for me with pg_create_physical_replication_slot(). The regexp passed to run_command doesn't match the output at all.
• after removing the regex => \d bit, it doesn't seem to like the fact that the physical slot is inactive:
  'Argument "" isn't numeric in numeric ge (>=) at check_postgres.pl line 5216.
  POSTGRES_REPLICATION_SLOTS WARNING: DB "postgres" (host:/tmp/cptesting_socket) cp_testing_slot: (physical inactive) | time=0.02s cp_testing_slot=;0
• I haven't tried logical decoding slots yet
• there's quite a bunch of trailing whitespace and stray tabs

t/02_replication_slots.t:

#!perl

## Test the "replication_slots" action

use 5.006;
use strict;
use warnings;
use Data::Dumper;
use Test::More tests => 15;
use lib 't','.';
use CP_Testing;

use vars qw/$dbh $result $t $port $host $dbname/;

my $cp = CP_Testing->new( {default_action => 'replication_slots'} );

$dbh = $cp->test_database_handle();
$dbh->{AutoCommit} = 1;
$port = $cp->get_port();
$host = $cp->get_host();
$dbname = $cp->get_dbname;

diag "Connected as $port:$host:$dbname\n";

my $S = q{Action 'replication_slots'};
my $label = 'POSTGRES_REPLICATION_SLOTS';

$t = qq{$S self-identifies correctly};
$result = $cp->run(q{-w 0});
like ($result, qr{^$label}, $t);

$t = qq{$S identifies host};
like ($result, qr{host:$host}, $t);

$t = qq{$S reports no replication slots};
like ($result, qr{No replication slots found}, $t);

$t = qq{$S accepts valid -w input};
for my $arg (
     '1 MB',
     '1 GB',
    ) {
   like ($cp->run(qq{-w "$arg"}), qr{^$label}, "$t ($arg)");
}

$t = qq{$S rejects invalid -w input};
for my $arg (
     '-1 MB',
     'abc'
    ) {
   like ($cp->run(qq{-w "$arg"}), qr{^ERROR: Invalid size}, "$t ($arg)");
}

$dbh->do ("SELECT * FROM pg_create_physical_replication_slot('cp_testing_slot')");

$t = qq{$S reports replication slots};
$result = $cp->run(q{-w 0});
like ($result, qr{Some replication slots found}, $t);
# ... more tests here

$dbh->do ("SELECT pg_drop_replication_slot('cp_testing_slot')");

exit;

--- a/t/CP_Testing.pm
+++ b/t/CP_Testing.pm
@@ -143,6 +143,12 @@ sub test_database_handle {
             print $cfh qq{max_fsm_pages = 99999\n};
         }

+        ## >= 9.4
+        if ($imaj > 9 or ($imaj==9 and $imin >= 4)) {
+            print $cfh qq{wal_level = hot_standby\n};
+            print $cfh qq{max_replication_slots = 1\n};
+        }
+
         print $cfh "\n";
         close $cfh or die qq{Could not close "$cfile": $!\n};

[glynastill]

Thanks very much Christoph!

Looks like I never tested it on a physical replication slot that hadn't been "started up" yet with START_REPLICATION. This should be resolved now, as well as the sloppy whitespace.

I've added some test cases to the file you supplied, with most of the tests done on logical slots because of the requirement for physical slots to be started up, but the tests on the physical slots would be the same anyway so I'm not sure it's required.

If we needed to I guess we could start the physical slots up with psql over the replication protocol; that'd require a way to add the relevent entries in pg_hba.conf for the test_database and I couldn't see an existing way to do that ... and I didn't want to roll my own if there was a way to do it already?

[df7cb]

Thanks for the update, just pushed as a3ea525.

Physical slots were just what I was trying first, from skimming over your testcases the code looks very much good enough.