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Create ReplicaLagLimiter. Replace --max-lag, --check-interval, and --check-slave-lag with --replica-lag and --replica-lag-dsn. Use TableParser::get_table_status() in NibbleItertor. Eval SHOW TABLE STATUS. Auto-add "n" (name) part to parsed DSNs.
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Daniel Nichter
201
lib/ReplicaLagLimiter.pm
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201
lib/ReplicaLagLimiter.pm
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# 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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# and adjustment (-1=down/decrease, 0=none, 1=up/increase) based on
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# a moving average of how long operations are taking on the master.
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# Regardless of that, slaves may still lag, so <wait()> waits for them
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# to catchup 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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sub new {
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my ( $class, %args ) = @_;
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my @required_args = qw(spec slaves get_lag);
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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 ($spec) = @args{@required_args};
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my %specs = map {
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my ($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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target_time => 1, # optimal time for master ops
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sample_size => 5, # number of master ops to use for moving average
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max => 1, # max slave lag
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timeout => 3600, # max time to wait for all slaves to catchup
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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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samples => [], # master op times
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moving_avg => 0, # moving avgerge of samples
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get_lag => $args{get_lag},
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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 ) {
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die "invalid spec format, should be key=value: $spec\n";
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}
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if ( $key !~ m/(?:max|timeout|continue)/i ) {
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die "invalid spec: $spec\n";
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}
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if ( !$val ) {
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die "spec has no value: $spec\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: $spec\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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}
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sub update {
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my ($self, $t) = @_;
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MKDEBUG && _d('Sample time:', $t);
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my $sample_size = $self->{sample_size};
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my $samples = $self->{samples};
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my $adjust = 0;
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if ( @$samples == $sample_size ) {
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shift @$samples;
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push @$samples, $t;
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my $sum = 0;
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map { $sum += $_ } @$samples;
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$self->{moving_avg} = $sum / $sample_size;
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MKDEBUG && _d('Moving average:', $self->{moving_avg});
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$adjust = $self->{target_time} <=> $self->{moving_avg};
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}
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else {
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MKDEBUG && _d('Saving sample', @$samples + 1, 'of', $sample_size);
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push @$samples, $t;
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}
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return $adjust;
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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.
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#
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# Returns:
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# True if all slaves caught up, else 0 (timeout)
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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 catchup...\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->{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 ( $slave_no >= @$slave ) {
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MKDEBUG && _d('Timeout waiting for', $slaves->[$slave_no]->{dsn}->{n});
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return 0 unless $self->{continue};
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}
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MKDEBUG && _d('All slaves caught up');
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return 1;
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}
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sub _d {
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my ($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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