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=head1 NAME |
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|
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AnyEvent::Watchdog - generic watchdog/program restarter |
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|
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=head1 SYNOPSIS |
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|
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# MUST be use'd as the very first thing in the main program |
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use AnyEvent::Watchdog; |
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|
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=head1 DESCRIPTION |
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|
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This module implements a watchdog that can repeatedly fork the program and |
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thus effectively restart it - as soon as the module is use'd, it will fork |
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the program (if possible) and continue to run it normally in the child, |
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while the parent becomes a supervisor. |
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|
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The child can then ask the supervisor to restart itself instead of |
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exiting, or ask the supervisor to restart it gracefully or forcefully. |
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|
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B<NOTE:> This module B<< I<MUST> >> be used as the first thing in the main |
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program. It will cause weird effects when used from another module, as |
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perl does not expect to be forked inside C<BEGIN> blocks. |
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|
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=head1 RECIPES |
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|
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Use AnyEvent::Watchdog solely as a convinient on-demand-restarter: |
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|
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use AnyEvent::Watchdog; |
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|
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# and whenever you wnat to restart (e.g. to upgrade code): |
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AnyEvent::Watchdog::restart; |
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|
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Use AnyEvent::Watchdog to kill the program and exit when the event loop |
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fails to run for more than two minutes: |
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|
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use AnyEvent::Watchdog qw(autorestart heartbeat=120); |
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|
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Use AnyEvent::Watchdog to automatically restart the program |
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when it fails to handle events for longer than 5 minutes: |
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|
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use AnyEvent::Watchdog qw(autorestart heartbeat=300); |
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|
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=head1 FUNCTIONS |
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|
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The module supports the following functions: |
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|
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=over 4 |
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|
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=cut |
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|
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package AnyEvent::Watchdog; |
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|
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# load modules we will use later anyways |
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use common::sense; |
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|
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use Carp (); |
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|
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our $VERSION = '0.9'; |
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|
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our $PID; # child pid |
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our $ENABLED = 1; |
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our $AUTORESTART; # actually exit |
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our $HEARTBEAT; |
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our ($P, $C); |
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|
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sub poll($) { |
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(vec my $v, fileno $P, 1) = 1; |
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CORE::select $v, undef, undef, $_[0] |
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} |
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|
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sub server { |
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my $expected;# do we expect a program exit? |
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my $heartbeat; |
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|
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$AUTORESTART = 0; |
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|
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local $SIG{HUP} = 'IGNORE'; |
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local $SIG{INT} = 'IGNORE'; |
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local $SIG{TERM} = 'IGNORE'; |
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|
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while () { |
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if ($heartbeat) { |
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unless (poll $heartbeat) { |
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$expected = 1; |
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warn "AnyEvent::Watchdog: heartbeat failed. killing.\n"; |
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kill 9, $PID; |
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last; |
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} |
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} |
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|
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sysread $P, my $cmd, 1 |
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or last; |
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|
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if ($cmd eq chr 0) { |
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$AUTORESTART = 0; |
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|
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} elsif ($cmd eq chr 1) { |
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$AUTORESTART = 1; |
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|
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} elsif ($cmd eq chr 2) { |
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sysread $P, my $timeout, 1 |
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or last; |
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|
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$timeout = ord $timeout; |
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|
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unless (poll $timeout) { |
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warn "AnyEvent::Watchdog: program attempted restart, but failed to do so within $timeout seconds. killing.\n"; |
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kill 9, $PID; |
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} |
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|
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if (sysread $P, my $dummy, 1) { |
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warn "AnyEvent::Watchdog: unexpected program output. killing.\n"; |
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kill 9, $PID; |
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} |
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|
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$expected = 1; |
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last; |
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|
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} elsif ($cmd eq chr 3) { |
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sysread $P, my $interval, 1 |
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or last; |
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|
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$heartbeat = ord $interval; |
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|
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} elsif ($cmd eq chr 4) { |
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# heartbeat |
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# TODO: should only reset heartbeat timeout with \005 |
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|
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} else { |
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warn "AnyEvent::Watchdog: unexpected program output. killing.\n"; |
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kill 9, $PID; |
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last; |
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} |
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} |
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|
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waitpid $PID, 0; |
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|
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require POSIX; |
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|
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my $termsig = POSIX::WIFSIGNALED ($?) && POSIX::WTERMSIG ($?); |
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|
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if ($termsig == POSIX::SIGINT () || $termsig == POSIX::SIGTERM ()) { |
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$AUTORESTART = 0; |
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$expected = 1; |
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} |
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|
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unless ($expected) { |
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warn "AnyEvent::Watchdog: program exited unexpectedly with status $?.\n" |
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if $? >> 8; |
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} |
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|
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if ($AUTORESTART) { |
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warn "AnyEvent::Watchdog: attempting automatic restart.\n"; |
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} else { |
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if ($termsig) { |
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$SIG{$_} = 'DEFAULT' for keys %SIG; |
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kill $termsig, $$; |
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POSIX::_exit (127); |
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} else { |
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POSIX::_exit ($? >> 8); |
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} |
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} |
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} |
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|
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our %SEEKPOS; |
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# due to bugs in perl, try to remember file offsets for all fds, and restore them later |
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# (the parser otherwise exhausts the input files) |
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|
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# this causes perlio to flush its handles internally, so |
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# seek offsets become correct. |
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exec "."; # toi toi toi |
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#{ |
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# local $SIG{CHLD} = 'DEFAULT'; |
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# my $pid = fork; |
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# |
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# if ($pid) { |
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# waitpid $pid, 0; |
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# } else { |
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# kill 9, $$; |
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# } |
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#} |
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|
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# now record "all" fd positions, assuming 1023 is more than enough. |
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for (0 .. 1023) { |
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open my $fh, "<&$_" or next; |
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$SEEKPOS{$_} = (sysseek $fh, 0, 1 or next); |
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} |
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|
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while () { |
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if ($^O =~ /mswin32/i) { |
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require AnyEvent::Util; |
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($P, $C) = AnyEvent::Util::portable_socketpair () |
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or Carp::croak "AnyEvent::Watchdog: unable to create restarter pipe: $!\n"; |
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} else { |
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require Socket; |
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socketpair $P, $C, Socket::AF_UNIX (), Socket::SOCK_STREAM (), 0 |
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or Carp::croak "AnyEvent::Watchdog: unable to create restarter pipe: $!\n"; |
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} |
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local $SIG{CHLD} = 'DEFAULT'; |
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|
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$PID = fork; |
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|
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unless (defined $PID) { |
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warn "AnyEvent::Watchdog: '$!', retrying in one second...\n"; |
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sleep 1; |
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} elsif ($PID) { |
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close $C; |
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server; |
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} else { |
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# restore seek offsets |
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while (my ($k, $v) = each %SEEKPOS) { |
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open my $fh, "<&$k" or next; |
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sysseek $fh, $v, 0; |
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} |
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|
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# continue the program normally |
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close $P; |
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last; |
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} |
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} |
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=item AnyEvent::Watchdog::restart [$timeout] |
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Tells the supervisor to restart the process when it exits, or forcefully |
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after C<$timeout> seconds (minimum 1, maximum 255, default 60). |
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Calls C<exit 0> to exit the process cleanly. |
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|
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=cut |
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sub restart(;$) { |
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my ($timeout) = @_; |
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$timeout = 60 unless defined $timeout; |
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$timeout = 1 if $timeout < 1; |
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$timeout = 255 if $timeout > 255; |
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|
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syswrite $C, "\x01\x02" . chr $timeout; |
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exit 0; |
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} |
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|
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=item AnyEvent::Watchdog::autorestart [$boolean] |
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|
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=item use AnyEvent::Watchdog qw(autorestart[=$boolean]) |
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Enables or disables autorestart (initially disabled, default for |
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C<$boolean> is to enable): By default, the supervisor will exit if the |
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program exits or dies in any way. When enabling autorestart behaviour, |
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then the supervisor will try to restart the program after it dies. |
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|
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Note that the supervisor will never autorestart when the child died with |
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SIGINT or SIGTERM. |
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=cut |
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|
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sub autorestart(;$) { |
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syswrite $C, !@_ || $_[0] ? "\x01" : "\x00"; |
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} |
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|
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=item AnyEvent::Watchdog::heartbeat [$interval] |
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|
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=item use AnyEvent::Watchdog qw(heartbeat[=$interval]) |
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|
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Tells the supervisor to automatically kill the program if it doesn't |
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react for C<$interval> seconds (minium 1, maximum 255, default 60) , then |
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installs an AnyEvent timer the sends a regular heartbeat to the supervisor |
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twice as often. |
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|
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Exit behaviour isn't changed, so if you want a restart instead of an exit, |
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you have to call C<autorestart>. |
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|
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The heartbeat frequency can be changed as often as you want, an interval |
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of C<0> disables the heartbeat check again. |
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|
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=cut |
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|
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sub heartbeat(;$) { |
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my ($interval) = @_; |
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|
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$interval = 60 unless defined $interval; |
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$interval = 1 if $interval < 1; |
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$interval = 255 if $interval > 255; |
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|
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syswrite $C, "\x03" . chr $interval; |
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|
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require AE; |
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$HEARTBEAT = AE::timer (0, $interval * 0.5, sub { |
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syswrite $C, "\x04"; |
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}); |
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} |
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|
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sub import { |
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shift; |
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|
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for (@_) { |
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if (/^autorestart(?:=(.*))?$/) { |
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autorestart defined $1 ? $1 : 1; |
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} elsif (/^heartbeat(?:=(.*))?$/) { |
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heartbeat $1; |
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} else { |
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Carp::croak "AnyEvent::Watchdog: '$_' is not a valid import argument"; |
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} |
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} |
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} |
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|
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=back |
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|
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=head1 SEE ALSO |
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|
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L<AnyEvent>. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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|
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1 |
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