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Revision 1.386 by root, Mon Sep 26 11:32:19 2011 UTC vs.
Revision 1.387 by root, Sat Oct 1 22:39:29 2011 UTC

… …
415not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's 415not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
416pure perl implementation). 416pure perl implementation).
417 417
418=head3 Safe/Unsafe Signals 418=head3 Safe/Unsafe Signals
419 419
420Perl signals can be either "safe" (synchronous to opcode handling) or 420Perl signals can be either "safe" (synchronous to opcode handling)
421"unsafe" (asynchronous) - the former might get delayed indefinitely, the 421or "unsafe" (asynchronous) - the former might delay signal delivery
422latter might corrupt your memory. 422indefinitely, the latter might corrupt your memory.
423 423
424AnyEvent signal handlers are, in addition, synchronous to the event loop, 424AnyEvent signal handlers are, in addition, synchronous to the event loop,
425i.e. they will not interrupt your running perl program but will only be 425i.e. they will not interrupt your running perl program but will only be
426called as part of the normal event handling (just like timer, I/O etc. 426called as part of the normal event handling (just like timer, I/O etc.
427callbacks, too). 427callbacks, too).
428 428
429=head3 Signal Races, Delays and Workarounds 429=head3 Signal Races, Delays and Workarounds
430 430
431Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching 431Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
432callbacks to signals in a generic way, which is a pity, as you cannot 432attaching callbacks to signals in a generic way, which is a pity,
433do race-free signal handling in perl, requiring C libraries for 433as you cannot do race-free signal handling in perl, requiring
434this. AnyEvent will try to do its best, which means in some cases, 434C libraries for this. AnyEvent will try to do its best, which
435signals will be delayed. The maximum time a signal might be delayed is 435means in some cases, signals will be delayed. The maximum time
436specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This 436a signal might be delayed is 10 seconds by default, but can
437variable can be changed only before the first signal watcher is created, 437be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
438and should be left alone otherwise. This variable determines how often 438C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the Ö<ENVIRONMENT VARIABLES>
439AnyEvent polls for signals (in case a wake-up was missed). Higher values 439section for details.
440will cause fewer spurious wake-ups, which is better for power and CPU
441saving.
442 440
443All these problems can be avoided by installing the optional 441All these problems can be avoided by installing the optional
444L<Async::Interrupt> module, which works with most event loops. It will not 442L<Async::Interrupt> module, which works with most event loops. It will not
445work with inherently broken event loops such as L<Event> or L<Event::Lib> 443work with inherently broken event loops such as L<Event> or L<Event::Lib>
446(and not with L<POE> currently, as POE does its own workaround with 444(and not with L<POE> currently). For those, you just have to suffer the
447one-second latency). For those, you just have to suffer the delays. 445delays.
448 446
449=head2 CHILD PROCESS WATCHERS 447=head2 CHILD PROCESS WATCHERS
450 448
451 $w = AnyEvent->child (pid => <process id>, cb => <callback>); 449 $w = AnyEvent->child (pid => <process id>, cb => <callback>);
452 450
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1240our $VERSION = '6.02'; 1238our $VERSION = '6.02';
1241our $MODEL; 1239our $MODEL;
1242our @ISA; 1240our @ISA;
1243our @REGISTRY; 1241our @REGISTRY;
1244our $VERBOSE; 1242our $VERBOSE;
1245our $MAX_SIGNAL_LATENCY = 10;
1246our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred 1243our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
1244our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
1247 1245
1248BEGIN { 1246BEGIN {
1249 require "AnyEvent/constants.pl"; 1247 require "AnyEvent/constants.pl";
1250 1248
1251 eval "sub TAINT (){" . (${^TAINT}*1) . "}"; 1249 eval "sub TAINT (){" . (${^TAINT}*1) . "}";
… …
2227 2225
2228The default value for the C<max_outstanding> parameter for the default DNS 2226The default value for the C<max_outstanding> parameter for the default DNS
2229resolver - this is the maximum number of parallel DNS requests that are 2227resolver - this is the maximum number of parallel DNS requests that are
2230sent to the DNS server. 2228sent to the DNS server.
2231 2229
2230=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
2231
2232Perl has inherently racy signal handling (you can basically choose between
2233losing signals and memory corruption) - pure perl event loops (including
2234C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
2235have to poll regularly to avoid losing signals.
2236
2237Some event loops are racy, but don't poll regularly, and some event loops
2238are written in C but are still racy. For those event loops, AnyEvent
2239installs a timer that regularly wakes up the event loop.
2240
2241By default, the interval for this timer is C<10> seconds, but you can
2242override this delay with this environment variable (or by setting
2243the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
2244watchers).
2245
2246Lower values increase CPU (and energy) usage, higher values can introduce
2247long delays when reaping children or waiting for signals.
2248
2249The L<AnyEvent::Async> module, if available, will be used to avoid this
2250polling (with most event loops).
2251
2232=item C<PERL_ANYEVENT_RESOLV_CONF> 2252=item C<PERL_ANYEVENT_RESOLV_CONF>
2233 2253
2234The absolute path to a F<resolv.conf>-style file to use instead of 2254The absolute path to a F<resolv.conf>-style file to use instead of
2235F</etc/resolv.conf> (or the OS-specific configuration) in the default 2255F</etc/resolv.conf> (or the OS-specific configuration) in the default
2236resolver, or the empty string to select the default configuration. 2256resolver, or the empty string to select the default configuration.

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