[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 1.71 by root, Wed Aug 21 08:40:28 2013 UTC

     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.
               };
            }
            $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
            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
               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.
 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::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 I haven't heard anybody complaining
+        about it yet).
+    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
-        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).
         "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.
         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
     AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
     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 1.71 by root, Wed Aug 21 08:40:28 2013 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC vs.
Revision 1.71 by root, Wed Aug 21 08:40:28 2013 UTC