mirror of
https://github.com/percona/percona-toolkit.git
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227 lines
7.6 KiB
Perl
227 lines
7.6 KiB
Perl
# This program is copyright 2011 Percona Inc.
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# Feedback and improvements are welcome.
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#
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# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
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# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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#
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# This program is free software; you can redistribute it and/or modify it under
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# the terms of the GNU General Public License as published by the Free Software
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# Foundation, version 2; OR the Perl Artistic License. On UNIX and similar
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# systems, you can issue `man perlgpl' or `man perlartistic' to read these
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# licenses.
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#
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# You should have received a copy of the GNU General Public License along with
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# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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# Place, Suite 330, Boston, MA 02111-1307 USA.
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# ###########################################################################
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# ReplicaLagLimiter package
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# ###########################################################################
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{
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# Package: ReplicaLagLimiter
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# ReplicaLagLimiter helps limit slave lag when working on the master.
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# There are two sides to this problem: operations on the master and
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# slave lag. Master ops that replicate can affect slave lag, so they
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# should be adjusted to prevent overloading slaves. <update()> returns
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# an adjusted "n" value (number of whatever the master is doing) based
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# on a weighted decaying average of "t", how long operations are taking.
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# The desired master op time range is specified by target_t.
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#
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# Regardless of all that, slaves may still lag, so <wait()> waits for them
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# to catch up based on the spec passed to <new()>.
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package ReplicaLagLimiter;
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use strict;
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use warnings FATAL => 'all';
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use English qw(-no_match_vars);
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use constant MKDEBUG => $ENV{MKDEBUG} || 0;
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use Time::HiRes qw(sleep time);
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# Sub: new
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#
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# Required Arguments:
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# spec - --replicat-lag spec (arrayref of option=value pairs)
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# slaves - Arrayref of slave cxn, like [{dsn=>{...}, dbh=>...},...]
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# get_lag - Callback passed slave dbh and returns slave's lag
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# initial_n - Initial n value for <update()>
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# initial_t - Initial t value for <update()>
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# target_t - Target time for t in <update()>
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#
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# Optional Arguments:
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# weight - Weight of previous n/t values (default 0.75).
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#
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# Returns:
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# ReplicaLagLimiter object
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sub new {
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my ( $class, %args ) = @_;
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my @required_args = qw(spec slaves get_lag initial_n initial_t target_t);
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foreach my $arg ( @required_args ) {
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die "I need a $arg argument" unless defined $args{$arg};
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}
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my ($spec) = @args{@required_args};
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my %specs = map {
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my ($key, $val) = split '=', $_;
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MKDEBUG && _d($key, '=', $val);
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lc($key) => $val;
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} @$spec;
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my $self = {
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max => 1, # max slave lag
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timeout => 3600, # max time to wait for all slaves to catch up
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check => 1, # sleep time between checking slave lag
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continue => 'no', # return true even if timeout
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%specs, # slave wait specs from caller
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slaves => $args{slaves},
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get_lag => $args{get_lag},
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avg_n => $args{initial_n},
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avg_t => $args{initial_t},
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target_t => $args{target_t},
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weight => $args{weight} || 0.75,
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};
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return bless $self, $class;
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}
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sub validate_spec {
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# Permit calling as ReplicaLagLimiter-> or ReplicaLagLimiter::
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shift @_ if $_[0] eq 'ReplicaLagLimiter';
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my ( $spec ) = @_;
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if ( @$spec == 0 ) {
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die "spec array requires at least a max value\n";
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}
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my $have_max;
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foreach my $op ( @$spec ) {
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my ($key, $val) = split '=', $op;
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if ( !$key || !$val ) {
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die "invalid spec format, should be option=value: $op\n";
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}
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if ( $key !~ m/(?:max|timeout|continue)/i ) {
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die "unknown option in spec: $op\n";
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}
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if ( $key ne 'continue' && $val !~ m/^\d+$/ ) {
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die "value must be an integer: $op\n";
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}
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if ( $key eq 'continue' && $val !~ m/(?:yes|no)/i ) {
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die "value for $key must be \"yes\" or \"no\"\n";
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}
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$have_max = 1 if $key eq 'max';
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}
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if ( !$have_max ) {
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die "max must be specified"
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}
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return 1;
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}
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# Sub: update
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# Update weighted decaying average of master operation time. Param n is
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# generic; it's how many of whatever the caller is doing (rows, checksums,
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# etc.). Param s is how long this n took, in seconds (hi-res or not).
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#
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# Parameters:
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# n - Number of operations (rows, etc.)
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# t - Amount of time in seconds that n took
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#
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# Returns:
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# n adjust to meet target_t based on weighted decaying avg rate
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sub update {
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my ($self, $n, $t) = @_;
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MKDEBUG && _d('Master op time:', $n, 'n /', $t, 's');
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$self->{avg_n} = ($self->{avg_n} * $self->{weight}) + $n;
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$self->{avg_t} = ($self->{avg_t} * $self->{weight}) + $t;
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$self->{avg_rate} = $self->{avg_n} / $self->{avg_t};
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MKDEBUG && _d('Weighted avg rate:', $self->{avg_rate}, 'n/s');
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my $new_n = int($self->{avg_rate} * $self->{target_t});
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MKDEBUG && _d('Adjust n to', $new_n);
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return $new_n;
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}
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# Sub: wait_for_slave
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# Wait for Seconds_Behind_Master on all slaves to become < max.
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#
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# Optional Arguments:
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# Progress - <Progress> object to report waiting
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#
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# Returns:
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# 1 if all slaves catch up before timeout, else 0 if continue=yes, else die.
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sub wait {
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my ( $self, %args ) = @_;
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my @required_args = qw();
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foreach my $arg ( @required_args ) {
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die "I need a $arg argument" unless $args{$arg};
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}
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my $pr = $args{Progres};
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my $get_lag = $self->{get_lag};
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my $slaves = $self->{slaves};
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my $n_slaves = @$slaves;
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my $pr_callback;
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if ( $pr ) {
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# If you use the default Progress report callback, you'll need to
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# to add Transformers.pm to this tool.
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my $reported = 0;
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$pr_callback = sub {
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my ($fraction, $elapsed, $remaining, $eta, $slave_no) = @_;
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if ( !$reported ) {
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print STDERR "Waiting for replica "
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. ($slaves->[$slave_no]->{dsn}->{n} || '')
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. " to catch up...\n";
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$reported = 1;
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}
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else {
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print STDERR "Still waiting ($elapsed seconds)...\n";
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}
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return;
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};
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$pr->set_callback($pr_callback);
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}
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my ($max, $check, $timeout) = @{$self}{qw(max check timeout)};
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my $slave_no = 0;
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my $slave = $slaves->[$slave_no];
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my $t_start = time;
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while ($slave && time - $t_start < $timeout) {
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MKDEBUG && _d('Checking slave lag on', $slave->{dsn}->{n});
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my $lag = $get_lag->($slave->{dbh});
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if ( !defined $lag || $lag > $max ) {
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MKDEBUG && _d('Replica lag', $lag, '>', $max, '; sleeping', $check);
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$pr->update(sub { return $slave_no; }) if $pr;
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sleep $check;
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}
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else {
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MKDEBUG && _d('Replica ready, lag', $lag, '<=', $max);
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$slave = $slaves->[++$slave_no];
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}
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}
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if ( $slave_no < @$slaves ) {
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if ( $self->{continue} eq 'no' ) {
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die "Timeout waiting for replica " . $slaves->[$slave_no]->{dsn}->{n}
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. " to catch up\n";
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}
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else {
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MKDEBUG && _d('Some slave are not caught up');
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return 0; # not ready
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}
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}
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MKDEBUG && _d('All slaves caught up');
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return 1; # ready
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}
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sub _d {
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my ($package, undef, $line) = caller 0;
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@_ = map { (my $temp = $_) =~ s/\n/\n# /g; $temp; }
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map { defined $_ ? $_ : 'undef' }
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@_;
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print STDERR "# $package:$line $PID ", join(' ', @_), "\n";
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}
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1;
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}
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# ###########################################################################
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# End ReplicaLagLimiter package
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# ###########################################################################
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