Re: Warm standby problems

["David F. Skoll" <dfs@xxxxxxxxxxxxxxxxxx>]

Tom Lane wrote:

> What about the other direction: the script invoked by the archive
> returns "done" before the bits have all been shipped?

Do you mean the wal_archive_command?  It waits for scp to finish.
It's written in Perl; here is the relevant part.

Regards,

David.

[Stuff deleted...]

my $remote_user      = $failover->get_setting('backup_ssh_user');
my $remote_host      = $failover->get_setting('backup_db_host');
my $remote_directory = $failover->get_setting('backup_wal_dir');
my $postgres_user    = $failover->get_setting('pg_userid') || 'postgres';

my $pid = open(CHILD, '-|');
my $wal_filename_only;
(undef, undef, $wal_filename_only) = File::Spec->splitpath( $wal_file );

if( $pid ) { # Parent

	while(<CHILD>) {
		chomp;
		canit_log( "Output from scp: $_" );
	}

	# This should wait for scp to finish
	my $rc = close CHILD;
	my $errno = $!;
	my $child_error = $?;
	alarm(0);

	if( ! $rc ) {
		if( $errno ) {
			canit_warning("Error closing pipe from scp: $errno");
			exit EXIT_FAILURE;
		} elsif ($child_error & 127) {
			canit_warning("scp died with signal " . ($child_error & 127));
			exit EXIT_FAILURE;
		} else {
			canit_warning("scp exited with non-zero exit code " . ($child_error >> 8));
			exit EXIT_FAILURE;
		}
	}

	my $exit_status = EXIT_OK;
	if (system('ssh', "$remote_user\@$remote_host", "chown $postgres_user $remote_directory/$wal_filename_only.NEW") != 0) {
		canit_warning("ssh command to chown remote file failed: $?");
		$exit_status = EXIT_FAILURE;
	}

	if (system('ssh', "$remote_user\@$remote_host", "mv -f $remote_directory/$wal_filename_only.NEW $remote_directory/$wal_filename_only") != 0) {
		canit_warning("ssh command to rename remote file failed: $?");
		$exit_status = EXIT_FAILURE;
	}

	if ($exit_status == EXIT_OK) {
		canit_log("Successully archived WAL file $wal_filename_only on $remote_host");
	}

	exit $exit_status;
}

# In the child:
# Make sure we capture STDERR
open(STDERR, '>&STDOUT');

# In new scope to suppress warning about code after an exec - see
# 'perldoc exec' for details
{
	no warnings 'exec';
	exec 'scp', '-q', $wal_file, "$remote_user\@$remote_host:$remote_directory/$wal_filename_only.NEW";
}

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