[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC

 NAME
     AnyEvent - the DBI of event loop programming
-    EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
+    EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode,
-    Qt, FLTK and POE are various supported event loops/environments.
+    IO::Async, Qt, FLTK and POE are various supported event
+    loops/environments.
 SYNOPSIS
        use AnyEvent;
        # if you prefer function calls, look at the AE manpage for
     Example 2: fire an event after 0.5 seconds, then roughly every second.
        my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
           warn "timeout\n";
-       };
+       });
    TIMING ISSUES
     There are two ways to handle timers: based on real time (relative, "fire
     in 10 seconds") and based on wallclock time (absolute, "fire at 12
     o'clock").
     will not restart syscalls (that includes Async::Interrupt and AnyEvent's
     pure perl implementation).
    Safe/Unsafe Signals
     Perl signals can be either "safe" (synchronous to opcode handling) or
-    "unsafe" (asynchronous) - the former might get delayed indefinitely, the
+    "unsafe" (asynchronous) - the former might delay signal delivery
-    latter might corrupt your memory.
+    indefinitely, the latter might corrupt your memory.
     AnyEvent signal handlers are, in addition, synchronous to the event
     loop, i.e. they will not interrupt your running perl program but will
     only be called as part of the normal event handling (just like timer,
     I/O etc. callbacks, too).
    Signal Races, Delays and Workarounds
     Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
     callbacks to signals in a generic way, which is a pity, as you cannot do
     race-free signal handling in perl, requiring C libraries for this.
     AnyEvent will try to do its best, which means in some cases, signals
-    will be delayed. The maximum time a signal might be delayed is specified
+    will be delayed. The maximum time a signal might be delayed is 10
-    in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
+    seconds by default, but can be overriden via
-    can be changed only before the first signal watcher is created, and
+    $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
-    should be left alone otherwise. This variable determines how often
+    - see the "ENVIRONMENT VARIABLES" section for details.
-    AnyEvent polls for signals (in case a wake-up was missed). Higher values
-    will cause fewer spurious wake-ups, which is better for power and CPU
-    saving.
     All these problems can be avoided by installing the optional
     Async::Interrupt module, which works with most event loops. It will not
     work with inherently broken event loops such as Event or Event::Lib (and
-    not with POE currently, as POE does its own workaround with one-second
-    latency). For those, you just have to suffer the delays.
+    not with POE currently). For those, you just have to suffer the delays.
   CHILD PROCESS WATCHERS
        $w = AnyEvent->child (pid => <process id>, cb => <callback>);
     You can also watch for a child process exit and catch its exit status.
     Example: fork a process and wait for it
        my $done = AnyEvent->condvar;
+       # this forks and immediately calls exit in the child. this
+       # normally has all sorts of bad consequences for your parent,
+       # so take this as an example only. always fork and exec,
+       # or call POSIX::_exit, in real code.
        my $pid = fork or exit 5;
        my $w = AnyEvent->child (
           pid => $pid,
           cb  => sub {
         This works because for every event source (EOF on file handle),
         there is one call to "begin", so the condvar waits for all calls to
         "end" before sending.
         The ping example mentioned above is slightly more complicated, as
-        the there are results to be passwd back, and the number of tasks
+        the there are results to be passed back, and the number of tasks
         that are begun can potentially be zero:
            my $cv = AnyEvent->condvar;
            my %result;
               };
            }
            $cv->end;
+           ...
+           my $results = $cv->recv;
         This code fragment supposedly pings a number of hosts and calls
         "send" after results for all then have have been gathered - in any
         order. To achieve this, the code issues a call to "begin" when it
         starts each ping request and calls "end" when it has received some
         result for it. Since "begin" and "end" only maintain a counter, the
         In list context, all parameters passed to "send" will be returned,
         in scalar context only the first one will be returned.
         Note that doing a blocking wait in a callback is not supported by
         any event loop, that is, recursive invocation of a blocking "->recv"
-        is not allowed, and the "recv" call will "croak" if such a condition
+        is not allowed and the "recv" call will "croak" if such a condition
-        is detected. This condition can be slightly loosened by using
+        is detected. This requirement can be dropped by relying on
-        Coro::AnyEvent, which allows you to do a blocking "->recv" from any
+        Coro::AnyEvent , which allows you to do a blocking "->recv" from any
-        thread that doesn't run the event loop itself.
+        thread that doesn't run the event loop itself. Coro::AnyEvent is
+        loaded automatically when Coro is used with AnyEvent, so code does
+        not need to do anything special to take advantage of that: any code
+        that would normally block your program because it calls "recv", be
+        executed in an "async" thread instead without blocking other
+        threads.
         Not all event models support a blocking wait - some die in that case
         (programs might want to do that to stay interactive), so *if you are
         using this from a module, never require a blocking wait*. Instead,
         let the caller decide whether the call will block or not (for
     $bool = $cv->ready
         Returns true when the condition is "true", i.e. whether "send" or
         "croak" have been called.
     $cb = $cv->cb ($cb->($cv))
-        This is a mutator function that returns the callback set and
+        This is a mutator function that returns the callback set (or "undef"
-        optionally replaces it before doing so.
+        if not) and optionally replaces it before doing so.
         The callback will be called when the condition becomes "true", i.e.
         when "send" or "croak" are called, with the only argument being the
         condition variable itself. If the condition is already true, the
         callback is called immediately when it is set. Calling "recv" inside
         the callback or at any later time is guaranteed not to block.
+        Additionally, when the callback is invoked, it is also removed from
+        the condvar (reset to "undef"), so the condvar does not keep a
+        reference to the callback after invocation.
 SUPPORTED EVENT LOOPS/BACKENDS
-    The available backend classes are (every class has its own manpage):
+    The following backend classes are part of the AnyEvent distribution
+    (every class has its own manpage):
     Backends that are autoprobed when no other event loop can be found.
         EV is the preferred backend when no other event loop seems to be in
         use. If EV is not installed, then AnyEvent will fall back to its own
         pure-perl implementation, which is available everywhere as it comes
         by the main program.
            AnyEvent::Impl::Event     based on Event, very stable, few glitches.
            AnyEvent::Impl::Glib      based on Glib, slow but very stable.
            AnyEvent::Impl::Tk        based on Tk, very broken.
+           AnyEvent::Impl::UV        based on UV, innovated square wheels.
            AnyEvent::Impl::EventLib  based on Event::Lib, leaks memory and worse.
            AnyEvent::Impl::POE       based on POE, very slow, some limitations.
            AnyEvent::Impl::Irssi     used when running within irssi.
            AnyEvent::Impl::IOAsync   based on IO::Async.
            AnyEvent::Impl::Cocoa     based on Cocoa::EventLoop.
-           AnyEvent::Impl::FLTK2     based on FLTK (fltk 2 binding).
+           AnyEvent::Impl::FLTK      based on FLTK (fltk 2 binding).
     Backends with special needs.
         Qt requires the Qt::Application to be instantiated first, but will
         otherwise be picked up automatically. As long as the main program
         instantiates the application before any AnyEvent watchers are
         POE backend, so it can be supported through POE.
         AnyEvent knows about both Prima and Wx, however, and will try to
         load POE when detecting them, in the hope that POE will pick them
         up, in which case everything will be automatic.
+    Known event loops outside the AnyEvent distribution
+        The following event loops or programs support AnyEvent by providing
+        their own AnyEvent backend. They will be picked up automatically.
+           urxvt::anyevent           available to rxvt-unicode extensions
 GLOBAL VARIABLES AND FUNCTIONS
     These are not normally required to use AnyEvent, but can be useful to
     write AnyEvent extension modules.
     $guard = AnyEvent::post_detect { BLOCK }
         Arranges for the code block to be executed as soon as the event
         model is autodetected (or immediately if that has already happened).
         The block will be executed *after* the actual backend has been
-        detected ($AnyEvent::MODEL is set), but *before* any watchers have
+        detected ($AnyEvent::MODEL is set), so it is possible to do some
-        been created, so it is possible to e.g. patch @AnyEvent::ISA or do
+        initialisation only when AnyEvent is actually initialised - see the
-        other initialisations - see the sources of AnyEvent::Strict or
-        AnyEvent::AIO to see how this is used.
+        sources of AnyEvent::AIO to see how this is used.
         The most common usage is to create some global watchers, without
-        forcing event module detection too early, for example, AnyEvent::AIO
+        forcing event module detection too early. For example, AnyEvent::AIO
         creates and installs the global IO::AIO watcher in a "post_detect"
         block to avoid autodetecting the event module at load time.
         If called in scalar or list context, then it creates and returns an
         object that automatically removes the callback again when it is
            # able to just C<undef $WATCHER> if the watcher causes them grief.
            $WATCHER ||= $guard;
     @AnyEvent::post_detect
-        If there are any code references in this array (you can "push" to it
+        This is a lower level interface then "AnyEvent::post_detect" (the
-        before or after loading AnyEvent), then they will be called directly
+        function). This variable is mainly useful for modules that can do
+        something useful when AnyEvent is used and thus want to know when it
+        is initialised, but do not need to even load it by default. This
+        array provides the means to hook into AnyEvent passively, without
+        loading it.
+        Here is how it works: If there are any code references in this array
+        (you can "push" to it before or after loading AnyEvent), then they
-        after the event loop has been chosen.
+        will be called directly after the event loop has been chosen.
         You should check $AnyEvent::MODEL before adding to this array,
         though: if it is defined then the event loop has already been
         detected, and the array will be ignored.
         Best use "AnyEvent::post_detect { BLOCK }" when your application
         allows it, as it takes care of these details.
-        This variable is mainly useful for modules that can do something
-        useful when AnyEvent is used and thus want to know when it is
-        initialised, but do not need to even load it by default. This array
-        provides the means to hook into AnyEvent passively, without loading
-        it.
         Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
         together, you could put this into Coro (this is the actual code used
         by Coro to accomplish this):
         To understand the usefulness of this function, consider a function
         that asynchronously does something for you and returns some
         transaction object or guard to let you cancel the operation. For
         example, "AnyEvent::Socket::tcp_connect":
-           # start a conenction attempt unless one is active
+           # start a connection attempt unless one is active
            $self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
               delete $self->{connect_guard};
               ...
            };
               if $some_error_condition;
     AnyEvent::log $level, $msg[, @args]
         Log the given $msg at the given $level.
+        If AnyEvent::Log is not loaded then this function makes a simple
+        test to see whether the message will be logged. If the test succeeds
-        Loads AnyEvent::Log on first use and calls "AnyEvent::Log::log" -
+        it will load AnyEvent::Log and call "AnyEvent::Log::log" -
         consequently, look at the AnyEvent::Log documentation for details.
+        If the test fails it will simply return. Right now this happens when
+        a numerical loglevel is used and it is larger than the level
+        specified via $ENV{PERL_ANYEVENT_VERBOSE}.
         If you want to sprinkle loads of logging calls around your code,
         consider creating a logger callback with the "AnyEvent::Log::logger"
-        function.
+        function, which can reduce typing, codesize and can reduce the
+        logging overhead enourmously.
+    AnyEvent::fh_block $filehandle
+    AnyEvent::fh_unblock $filehandle
+        Sets blocking or non-blocking behaviour for the given filehandle.
 WHAT TO DO IN A MODULE
     As a module author, you should "use AnyEvent" and call AnyEvent methods
     freely, but you should not load a specific event module or rely on it.
     modules come as part of AnyEvent, the others are available via CPAN (see
     <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
     non-exhaustive list), and the list is heavily biased towards modules of
     the AnyEvent author himself :)
-    AnyEvent::Util
+    AnyEvent::Util (part of the AnyEvent distribution)
         Contains various utility functions that replace often-used blocking
         functions such as "inet_aton" with event/callback-based versions.
-    AnyEvent::Socket
+    AnyEvent::Socket (part of the AnyEvent distribution)
         Provides various utility functions for (internet protocol) sockets,
         addresses and name resolution. Also functions to create non-blocking
         tcp connections or tcp servers, with IPv6 and SRV record support and
         more.
-    AnyEvent::Handle
+    AnyEvent::Handle (part of the AnyEvent distribution)
         Provide read and write buffers, manages watchers for reads and
         writes, supports raw and formatted I/O, I/O queued and fully
         transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
-    AnyEvent::DNS
+    AnyEvent::DNS (part of the AnyEvent distribution)
         Provides rich asynchronous DNS resolver capabilities.
     AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
     AnyEvent::IGS, AnyEvent::FCP
         Implement event-based interfaces to the protocols of the same name
         (for the curious, IGS is the International Go Server and FCP is the
         Freenet Client Protocol).
-    AnyEvent::Handle::UDP
+    AnyEvent::AIO (part of the AnyEvent distribution)
-        Here be danger!
-        As Pauli would put it, "Not only is it not right, it's not even
-        wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
-        most notably its use of a stream-based API with a protocol that
-        isn't streamable, that the only way to improve it is to delete it.
-        It features data corruption (but typically only under load) and
-        general confusion. On top, the author is not only clueless about UDP
-        but also fact-resistant - some gems of his understanding: "connect
-        doesn't work with UDP", "UDP packets are not IP packets", "UDP only
-        has datagrams, not packets", "I don't need to implement proper error
-        checking as UDP doesn't support error checking" and so on - he
-        doesn't even understand what's wrong with his module when it is
-        explained to him.
-    AnyEvent::DBI
-        Executes DBI requests asynchronously in a proxy process for you,
-        notifying you in an event-based way when the operation is finished.
-    AnyEvent::AIO
         Truly asynchronous (as opposed to non-blocking) I/O, should be in
         the toolbox of every event programmer. AnyEvent::AIO transparently
         fuses IO::AIO and AnyEvent together, giving AnyEvent access to
         event-based file I/O, and much more.
+    AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
+    AnyEvent::Fork::Remote
+        These let you safely fork new subprocesses, either locally or
+        remotely (e.g.v ia ssh), using some RPC protocol or not, without the
+        limitations normally imposed by fork (AnyEvent works fine for
+        example). Dynamically-resized worker pools are obviously included as
+        well.
+        And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
+        just to exec external programs can easily beat using "fork" and
+        "exec" (or even "system") in most programs.
+    AnyEvent::Filesys::Notify
+        AnyEvent is good for non-blocking stuff, but it can't detect file or
+        path changes (e.g. "watch this directory for new files", "watch this
+        file for changes"). The AnyEvent::Filesys::Notify module promises to
+        do just that in a portbale fashion, supporting inotify on GNU/Linux
+        and some weird, without doubt broken, stuff on OS X to monitor
+        files. It can fall back to blocking scans at regular intervals
+        transparently on other platforms, so it's about as portable as it
+        gets.
+        (I haven't used it myself, but it seems the biggest problem with it
+        is it quite bad performance).
-    AnyEvent::HTTPD
+    AnyEvent::DBI
-        A simple embedded webserver.
+        Executes DBI requests asynchronously in a proxy process for you,
+        notifying you in an event-based way when the operation is finished.
     AnyEvent::FastPing
         The fastest ping in the west.
     Coro
-        Has special support for AnyEvent via Coro::AnyEvent.
+        Has special support for AnyEvent via Coro::AnyEvent, which allows
+        you to simply invert the flow control - don't call us, we will call
+        you:
+           async {
+              Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
+              print "5 seconds later!\n";
+              Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
+              my $line = <STDIN>; # works for ttys
+              AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
+              my ($body, $hdr) = Coro::rouse_wait;
+           };
 SIMPLIFIED AE API
     Starting with version 5.0, AnyEvent officially supports a second, much
     simpler, API that is designed to reduce the calling, typing and memory
     overhead by using function call syntax and a fixed number of parameters.
     The pure perl event loop simply re-throws the exception (usually within
     "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
     Glib uses "install_exception_handler" and so on.
 ENVIRONMENT VARIABLES
-    The following environment variables are used by this module or its
+    AnyEvent supports a number of environment variables that tune the
-    submodules.
+    runtime behaviour. They are usually evaluated when AnyEvent is loaded,
+    initialised, or a submodule that uses them is loaded. Many of them also
+    cause AnyEvent to load additional modules - for example,
+    "PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
+    loaded.
-    Note that AnyEvent will remove *all* environment variables starting with
+    All the environment variables documented here start with
-    "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
+    "PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
-    enabled.
+    Other modules are encouraged (but by no means required) to use
+    "PERL_ANYEVENT_SUBMODULE" if they have registered the
+    AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
+    AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
+    should not access env variables starting with "AE_", see below).
+    All variables can also be set via the "AE_" prefix, that is, instead of
+    setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
+    there is a clash btween anyevent and another program that uses
+    "AE_something" you can set the corresponding "PERL_ANYEVENT_something"
+    variable to the empty string, as those variables take precedence.
+    When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
+    their "PERL_ANYEVENT_xxx" counterpart unless that variable already
+    exists. If taint mode is on, then AnyEvent will remove *all* environment
+    variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
+    "undef" or the empty string, if the corresaponding "AE_" variable is
+    set).
+    The exact algorithm is currently:
+       1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
+       2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
+       3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
+    This ensures that child processes will not see the "AE_" variables.
+    The following environment variables are currently known to AnyEvent:
     "PERL_ANYEVENT_VERBOSE"
-        By default, AnyEvent will be completely silent except in fatal
+        By default, AnyEvent will log messages with loglevel 4 ("error") or
-        conditions. You can set this environment variable to make AnyEvent
+        higher (see AnyEvent::Log). You can set this environment variable to
-        more talkative.
+        a numerical loglevel to make AnyEvent more (or less) talkative.
+        If you want to do more than just set the global logging level you
+        should have a look at "PERL_ANYEVENT_LOG", which allows much more
+        complex specifications.
+        When set to 0 ("off"), then no messages whatsoever will be logged
+        with everything else at defaults.
-        When set to 5 or higher, causes AnyEvent to warn about unexpected
+        When set to 5 or higher ("warn"), AnyEvent warns about unexpected
         conditions, such as not being able to load the event model specified
-        by "PERL_ANYEVENT_MODEL".
+        by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
+        - this is the minimum recommended level for use during development.
-        When set to 7 or higher, cause AnyEvent to report to STDERR which
+        When set to 7 or higher (info), AnyEvent reports which event model
-        event model it chooses.
+        it chooses.
-        When set to 8 or higher, then AnyEvent will report extra information
+        When set to 8 or higher (debug), then AnyEvent will report extra
-        on which optional modules it loads and how it implements certain
+        information on which optional modules it loads and how it implements
-        features.
+        certain features.
+    "PERL_ANYEVENT_LOG"
+        Accepts rather complex logging specifications. For example, you
+        could log all "debug" messages of some module to stderr, warnings
+        and above to stderr, and errors and above to syslog, with:
+           PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
+        For the rather extensive details, see AnyEvent::Log.
+        This variable is evaluated when AnyEvent (or AnyEvent::Log) is
+        loaded, so will take effect even before AnyEvent has initialised
+        itself.
+        Note that specifying this environment variable causes the
+        AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
+        does not, so only using the latter saves a few hundred kB of memory
+        unless a module explicitly needs the extra features of
+        AnyEvent::Log.
     "PERL_ANYEVENT_STRICT"
         AnyEvent does not do much argument checking by default, as thorough
         argument checking is very costly. Setting this variable to a true
         value will cause AnyEvent to load "AnyEvent::Strict" and then to
         is definitely recommended to keep it off in production. Keeping
         "PERL_ANYEVENT_STRICT=1" in your environment while developing
         programs can be very useful, however.
     "PERL_ANYEVENT_DEBUG_SHELL"
-        If this env variable is set, then its contents will be interpreted
+        If this env variable is nonempty, then its contents will be
-        by "AnyEvent::Socket::parse_hostport" (after replacing every
+        interpreted by "AnyEvent::Socket::parse_hostport" and
-        occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
+        "AnyEvent::Debug::shell" (after replacing every occurance of $$ by
-        is bound on that port. The shell object is saved in
+        the process pid). The shell object is saved in
         $AnyEvent::Debug::SHELL.
-        This takes place when the first watcher is created.
+        This happens when the first watcher is created.
         For example, to bind a debug shell on a unix domain socket in
         /tmp/debug<pid>.sock, you could use this:
            PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
+           # connect with e.g.: socat readline /tmp/debug123.sock
+        Or to bind to tcp port 4545 on localhost:
+           PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
+           # connect with e.g.: telnet localhost 4545
-        Note that creating sockets in /tmp is very unsafe on multiuser
+        Note that creating sockets in /tmp or on localhost is very unsafe on
-        systems.
+        multiuser systems.
     "PERL_ANYEVENT_DEBUG_WRAP"
         Can be set to 0, 1 or 2 and enables wrapping of all watchers for
         debugging purposes. See "AnyEvent::Debug::wrap" for details.
         For example, to force the pure perl model (AnyEvent::Loop::Perl) you
         could start your program like this:
            PERL_ANYEVENT_MODEL=Perl perl ...
+    "PERL_ANYEVENT_IO_MODEL"
+        The current file I/O model - see AnyEvent::IO for more info.
+        At the moment, only "Perl" (small, pure-perl, synchronous) and
+        "IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
+        if AnyEvent::AIO can be loaded, otherwise it is "Perl".
     "PERL_ANYEVENT_PROTOCOLS"
         Used by both AnyEvent::DNS and AnyEvent::Socket to determine
         preferences for IPv4 or IPv6. The default is unspecified (and might
         change, or be the result of auto probing).
         mentioned will be used, and preference will be given to protocols
         mentioned earlier in the list.
         This variable can effectively be used for denial-of-service attacks
         against local programs (e.g. when setuid), although the impact is
-        likely small, as the program has to handle conenction and other
+        likely small, as the program has to handle connection and other
         failures anyways.
         Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
         IPv6, but support both and try to use both.
         "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
         resolve or contact IPv6 addresses.
         "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
         prefer IPv6 over IPv4.
+    "PERL_ANYEVENT_HOSTS"
+        This variable, if specified, overrides the /etc/hosts file used by
+        AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
+        read from that file instead.
     "PERL_ANYEVENT_EDNS0"
         Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
         for DNS. This extension is generally useful to reduce DNS traffic,
-        but some (broken) firewalls drop such DNS packets, which is why it
+        especially when DNSSEC is involved, but some (broken) firewalls drop
-        is off by default.
+        such DNS packets, which is why it is off by default.
         Setting this variable to 1 will cause AnyEvent::DNS to announce
         EDNS0 in its DNS requests.
     "PERL_ANYEVENT_MAX_FORKS"
     "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
         The default value for the "max_outstanding" parameter for the
         default DNS resolver - this is the maximum number of parallel DNS
         requests that are sent to the DNS server.
+    "PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
+        Perl has inherently racy signal handling (you can basically choose
+        between losing signals and memory corruption) - pure perl event
+        loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
+        available) therefore have to poll regularly to avoid losing signals.
+        Some event loops are racy, but don't poll regularly, and some event
+        loops are written in C but are still racy. For those event loops,
+        AnyEvent installs a timer that regularly wakes up the event loop.
+        By default, the interval for this timer is 10 seconds, but you can
+        override this delay with this environment variable (or by setting
+        the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
+        watchers).
+        Lower values increase CPU (and energy) usage, higher values can
+        introduce long delays when reaping children or waiting for signals.
+        The AnyEvent::Async module, if available, will be used to avoid this
+        polling (with most event loops).
     "PERL_ANYEVENT_RESOLV_CONF"
-        The file to use instead of /etc/resolv.conf (or OS-specific
+        The absolute path to a resolv.conf-style file to use instead of
-        configuration) in the default resolver. When set to the empty
+        /etc/resolv.conf (or the OS-specific configuration) in the default
-        string, no default config will be used.
+        resolver, or the empty string to select the default configuration.
     "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
         When neither "ca_file" nor "ca_path" was specified during
         AnyEvent::TLS context creation, and either of these environment
-        variables exist, they will be used to specify CA certificate
+        variables are nonempty, they will be used to specify CA certificate
         locations instead of a system-dependent default.
     "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
         When these are set to 1, then the respective modules are not loaded.
         Mostly good for testing AnyEvent itself.
           my $txn = shift;
           my $data = $txn->result;
           ...
        });
-       EV::loop;
+       EV::run;
     3b. The module user could use AnyEvent, too:
        use AnyEvent;
         This module is part of perl since release 5.008. It will be used
         when the chosen event library does not come with a timing source of
         its own. The pure-perl event loop (AnyEvent::Loop) will additionally
         load it to try to use a monotonic clock for timing stability.
+    AnyEvent::AIO (and IO::AIO)
+        The default implementation of AnyEvent::IO is to do I/O
+        synchronously, stopping programs while they access the disk, which
+        is fine for a lot of programs.
+        Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
+        switch to a true asynchronous implementation, so event processing
+        can continue even while waiting for disk I/O.
 FORK
     Most event libraries are not fork-safe. The ones who are usually are
     because they rely on inefficient but fork-safe "select" or "poll" calls
     - higher performance APIs such as BSD's kqueue or the dreaded Linux
     epoll are usually badly thought-out hacks that are incompatible with
     usually happens when the first AnyEvent watcher is created, or the
     library is loaded).
     If you have to fork, you must either do so *before* creating your first
     watcher OR you must not use AnyEvent at all in the child OR you must do
-    something completely out of the scope of AnyEvent.
+    something completely out of the scope of AnyEvent (see below).
     The problem of doing event processing in the parent *and* the child is
     much more complicated: even for backends that *are* fork-aware or
     fork-safe, their behaviour is not usually what you want: fork clones all
     watchers, that means all timers, I/O watchers etc. are active in both
-    parent and child, which is almost never what you want. USing "exec" to
+    parent and child, which is almost never what you want. Using "exec" to
-    start worker children from some kind of manage rprocess is usually
+    start worker children from some kind of manage prrocess is usually
     preferred, because it is much easier and cleaner, at the expense of
     having to have another binary.
+    In addition to logical problems with fork, there are also implementation
+    problems. For example, on POSIX systems, you cannot fork at all in Perl
+    code if a thread (I am talking of pthreads here) was ever created in the
+    process, and this is just the tip of the iceberg. In general, using fork
+    from Perl is difficult, and attempting to use fork without an exec to
+    implement some kind of parallel processing is almost certainly doomed.
+    To safely fork and exec, you should use a module such as Proc::FastSpawn
+    that let's you safely fork and exec new processes.
+    If you want to do multiprocessing using processes, you can look at the
+    AnyEvent::Fork module (and some related modules such as
+    AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
+    This module allows you to safely create subprocesses without any
+    limitations - you can use X11 toolkits or AnyEvent in the children
+    created by AnyEvent::Fork safely and without any special precautions.
 SECURITY CONSIDERATIONS
     AnyEvent can be forced to load any event model via
     $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
     to execute arbitrary code or directly gain access, it can easily be used
     Development/Debugging: AnyEvent::Strict (stricter checking),
     AnyEvent::Debug (interactive shell, watcher tracing).
     Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
-    Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
+    Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
     Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
     AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
     AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
-    AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
+    AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
+    AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
     Non-blocking handles, pipes, stream sockets, TCP clients and servers:
     AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
+    Asynchronous File I/O: AnyEvent::IO.
     Asynchronous DNS: AnyEvent::DNS.
     Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
     Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
     AnyEvent::HTTP.
 AUTHOR
        Marc Lehmann <schmorp@schmorp.de>
-       http://home.schmorp.de/
+       http://anyevent.schmorp.de

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Comparing AnyEvent/README (file contents): Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC vs. Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC