[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.70 by root, Fri Apr 13 09:57:41 2012 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").
     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 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.
     $AnyEvent::MODEL
     $guard = AnyEvent::post_detect { BLOCK }
         Arranges for the code block to be executed as soon as the event
         model is autodetected (or immediately if that has already happened).
         The block will be executed *after* the actual backend has been
-        detected ($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 you want to sprinkle loads of logging calls around your code,
         consider creating a logger callback with the "AnyEvent::Log::logger"
         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.
     Be careful when you create watchers in the module body - AnyEvent will
     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::AIO
+    AnyEvent::AIO (part of the AnyEvent distribution)
         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
         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 I haven't heard anybody complaining
+        (I haven't used it myself, but it seems the biggest problem with it
-        about it yet).
+        is it quite bad performance).
     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::HTTPD
-        A simple embedded webserver.
     AnyEvent::FastPing
         The fastest ping in the west.
     Coro
         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
           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.

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Comparing AnyEvent/README (file contents): Revision 1.70 by root, Fri Apr 13 09:57:41 2012 UTC vs. Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.70 by root, Fri Apr 13 09:57:41 2012 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC