NAME Coro::ProcessPool - an asynchronous process pool SYNOPSIS use Coro::ProcessPool; use Coro; my $pool = Coro::ProcessPool->new( max_procs => 4, max_reqs => 100, include => ['/path/to/my/task/classes', '/path/to/other/packages'], ); my $double = sub { $_[0] * 2 }; #----------------------------------------------------------------------- # Process in sequence #----------------------------------------------------------------------- my %result; foreach my $i (1 .. 1000) { $result{$i} = $pool->process($double, [$i]); } #----------------------------------------------------------------------- # Process as a batch #----------------------------------------------------------------------- my @results = $pool->map($double, 1 .. 1000); #----------------------------------------------------------------------- # Defer waiting for result #----------------------------------------------------------------------- my %deferred = map { $_ => $pool->defer($double, [$_]) } 1 .. 1000); foreach my $i (keys %deferred) { print "$i = " . $deferred{$i}->() . "\n"; } #----------------------------------------------------------------------- # Use a "task class", implementing 'new' and 'run' #----------------------------------------------------------------------- my $result = $pool->process('Task::Doubler', 21); #----------------------------------------------------------------------- # Pipelines (work queues) #----------------------------------------------------------------------- my $pipe = $pool->pipeline; # Start producer thread to queue tasks my $producer = async { while (my $task = get_next_task()) { $pipe->queue('Some::TaskClass', $task); } # Let the pipeline know no more tasks are coming $pipe->shutdown; }; # Collect the results of each task as they are received while (my $result = $pipe->next) { do_stuff_with($result); } $pool->shutdown; DESCRIPTION Processes tasks using a pool of external Perl processes. ATTRIBUTES max_procs The maximum number of processes to run within the process pool. Defaults to the number of CPUs on the ssytem. max_reqs The maximum number of tasks a worker process may run before being terminated and replaced with a fresh process. This is useful for tasks that might leak memory over time. include An optional array ref of directory paths to prepend to the set of directories the worker process will use to find Perl packages. PRIVATE ATTRIBUTES procs_lock Semaphore used to control access to the worker processes. Starts incremented to the number of processes ("max_procs"). num_procs Running total of processes that are currently running. procs Array holding the Coro::ProcessPool::Process objects. all_procs is_running Boolean which signals to the instance that the "shutdown" method has been called. METHODS capacity Returns the number of free worker processes. shutdown Shuts down all processes and resets state on the process pool. After calling this method, the pool is effectively in a new state and may be used normally. process($f, $args) Processes code ref $f in a child process from the pool. If $args is provided, it is an array ref of arguments that will be passed to $f. Returns the result of calling $f->(@$args). Alternately, $f may be the name of a class implementing the methods "new" and "run", in which case the result is equivalent to calling $f->new(@$args)->run(). Note that the include path for worker processes is identical to that of the calling process. This call will yield until the results become available. If all processes are busy, this method will block until one becomes available. Processes are spawned as needed, up to "max_procs", from this method. Also note that the use of "max_reqs" can cause this method to yield while a new process is spawned. map($f, @args) Applies $f to each value in @args in turn and returns a list of the results. Although the order in which each argument is processed is not guaranteed, the results are guaranteed to be in the same order as @args, even if the result of calling $f returns a list itself (in which case, the results of that calcuation is flattened into the list returned by "map". defer($f, $args) Similar to "process" in ., but returns immediately. The return value is a code reference that, when called, returns the results of calling "$f-"(@$args)>. my $deferred = $pool->defer($coderef, [ $x, $y, $z ]); my $result = $deferred->(); pipeline Returns a Coro::ProcessPool::Pipeline object which can be used to pipe requests through to the process pool. Results then come out the other end of the pipe. It is up to the calling code to perform task account (for example, by passing an id in as one of the arguments to the task class). my $pipe = $pool->pipeline; my $producer = async { foreach my $args (@tasks) { $pipe->queue('Some::Class', $args); } $pipe->shutdown; }; while (my $result = $pipe->next) { ... } All arguments to "pipeline()" are passed transparently to the constructor of Coro::ProcessPool::Pipeline. There is no limit to the number of pipelines which may be created for a pool. If the pool is shutdown while the pipeline is active, any tasks pending in Coro::ProcessPool::Pipeline::next will fail and cause the next call to "next()" to croak. A NOTE ABOUT IMPORTS AND CLOSURES Code refs are serialized using Storable to pass them to the worker processes. Once deserialized in the pool process, these functions can no longer see the stack as it is in the parent process. Therefore, imports and variables external to the function are unavailable. Something like this will not work: use Foo; my $foo = Foo->new(); my $result = $pool->process(sub { return $foo->bar; # $foo not found }); Nor will this: use Foo; my $result = $pool->process(sub { my $foo = Foo->new; # Foo not found return $foo->bar; }); The correct way to do this is to import from within the function: my $result = $pool->process(sub { require Foo; my $foo = Foo->new(); return $foo->bar; }); ...or to pass in external variables that are needed by the function: use Foo; my $foo = Foo->new(); my $result = $pool->process(sub { $_[0]->bar }, [ $foo ]); Use versus require The "use" pragma is run a compile time, whereas "require" is evaluated at runtime. Because of this, the use of "use" in code passed directly to the "process" method can fail because the "use" statement has already been evaluated when the calling code was compiled. This will not work: $pool->process(sub { use Foo; my $foo = Foo->new(); }); This will work: $pool->process(sub { require Foo; my $foo = Foo->new(); }); If "use" is necessary (for example, to import a method or transform the calling code via import), it is recommended to move the code into its own module, which can then be called in the anonymous routine: package Bar; use Foo; sub dostuff { ... } Then, in your caller: $pool->process(sub { require Bar; Bar::dostuff(); }); If it's a problem... Use the task class method if the loading requirements are causing headaches: my $result = $pool->process('Task::Class', [@args]); COMPATIBILITY "Coro::ProcessPool" will likely break on Win32 due to missing support for non-blocking file descriptors (Win32 can only call "select" and "poll" on actual network sockets). Without rewriting this as a network server, which would impact performance and be really annoying, it is likely this module will not support Win32 in the near future. The following modules will get you started if you wish to explore a synchronous process pool on Windows: Win32::Process Win32::IPC Win32::Pipe AUTHOR Jeff Ober COPYRIGHT AND LICENSE Copyright (C) 2013-2015, Jeff Ober. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. 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