Added tool proxysql_galera_writer.pl

tools/proxysql_galera_writer.pl

@@ -0,0 +1,99 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+use vars;
+use DBI;
+use DBD::mysql;
+
+
+## CUSTOMIZE THESE CONSTANTS
+use constant {
+	HOST => "127.0.0.1",
+	PORT => "6032",
+	USER => "admin",
+	PASS => "admin",
+	VERB => 1
+};
+
+our $dbn;
+our $dbh;
+
+sub main {
+	@ARGV = @_;
+	my $nargs=$#ARGV + 1;
+	if ($nargs != 3) {
+		print STDERR "Incorrect number of arguments\n";
+		return 1;
+	}
+	my $writerHG=$ARGV[0];
+	my $readerHG=$ARGV[1];
+	my $maxwriters=$ARGV[2];
+	if (VERB) {
+		print STDERR "Writer hostgroup: $writerHG\n";
+		print STDERR "Reader hostgroup: $readerHG\n";
+		print STDERR "Max num writers:  $maxwriters\n";
+	}
+	# connect to Admin interface and retrieve the current ative masters
+	$dbn="dbi:mysql:main:".HOST.":".PORT;
+	$dbh=DBI->connect($dbn, USER, PASS) or die "Unable to connect: $DBI::errstr\n";
+	my $selh=$dbh->prepare("SELECT hostname,port FROM runtime_mysql_servers WHERE status='ONLINE' AND hostgroup_id=$writerHG") or die "Unable to prepare: $DBI::errstr\n";
+	$selh->execute() or die "Unable to execute: $DBI::errstr\n";
+	my @data;
+	while (my $res=$selh->fetchrow_hashref) {
+		push (@data, $res);
+	}
+	my $active_writers= scalar @data;
+	if (VERB) {
+		print STDERR "Active writers found: $active_writers\n";
+		foreach (@data) {
+			my $s=$_;
+			print "	$s->{'hostname'} $s->{'port'}\n";
+		}
+	}
+	if ($active_writers==$maxwriters) {
+		if (VERB) {
+			print STDERR "Active writers match max number of writers: exit with no action\n";
+		}
+		return 0;
+	}
+	# if the execution of the script reaches here, some action is required
+	if (VERB) {
+		print STDERR "$active_writers active writers found do not match $maxwriters writers expected\n";
+	}
+	# although we run the check on runtime_mysql_servers , we will perform all the operations on mysql_servers
+	# be aware that in ProxySQL Admin doesn't support locking or transactions, so, even if unlikely,
+	# it is possible that race conditions can happen if two scripts update mysql_servers at the same
+
+	# first, set to OFFLINE_SOFT all nodes in the writer hostgroup
+	# OFFLINE_SOFT doesn't terminate current transactions, therefore it is a graceful "shutdown"
+	print STDERR "Disabling old $active_writers write(s)\n";	
+	$dbh->do("UPDATE mysql_servers SET status='OFFLINE_SOFT' WHERE hostgroup_id=$writerHG") or die "Unable to set writes offline: $DBI::errstr\n";
+
+	# here we define the new masters
+	# the algorithm used to determine the new masters is customizable: define the algorithm you prefer
+	# CUSTOMIZE IT!
+	print STDERR "Adding new $maxwriters write(s)\n";	
+
+	# in this example, the algorithm is that are promoted as master(s) the first N hosts order by ORDER BY weight DESC, hostname, port
+	$dbh->do("REPLACE INTO mysql_servers (hostgroup_id, hostname, port, status, weight, max_connections, use_ssl) SELECT $writerHG , hostname, port, status, weight, max_connections, use_ssl FROM mysql_servers WHERE hostgroup_id=$readerHG AND status='ONLINE' ORDER BY weight DESC, hostname, port LIMIT $maxwriters") or die "Unable to set new writer: $DBI::errstr\n";
+
+	# now we load at RUNTIME
+	print STDERR "Loading to runtime...";
+	$dbh->do("LOAD MYSQL SERVERS TO RUNTIME") or die "Unable to LOAD MYSQL SERVERS TO RUNTIME: $DBI::errstr\n";
+	print STDERR " Done!\n";
+	# as last step, we display the current masters
+	print STDERR "Reporting new writer(s) :\n";
+	$selh->execute() or die "Unable to execute: $DBI::errstr\n";
+	my @newhosts;
+	while (my $res=$selh->fetchrow_hashref) {
+		push (@newhosts, $res);
+	}
+	foreach (@newhosts) {
+		my $s=$_;
+		print "	$s->{'hostname'} $s->{'port'}\n";
+	}
+	return 0;
+}
+
+
+if(!caller) { exit(main(@ARGV)); }