IO::Async::Function(3)User Contributed Perl DocumentatioIO::Async::Function(3)NAME
"IO::Async::Function" - call a function asynchronously
SYNOPSIS
use IO::Async::Function;
use IO::Async::Loop;
my $loop = IO::Async::Loop->new;
my $function = IO::Async::Function->new(
code => sub {
my ( $number ) = @_;
return is_prime( $number );
},
);
$loop->add( $function );
$function->call(
args => [ 123454321 ],
on_return => sub {
my $isprime = shift;
print "123454321 " . ( $isprime ? "is" : "is not" ) . " a prime number\n";
},
on_error => sub {
print STDERR "Cannot determine if it's prime - $_[0]\n";
},
);
$loop->run;
DESCRIPTION
This subclass of IO::Async::Notifier wraps a function body in a
collection of worker processes, to allow it to execute independently of
the main process. The object acts as a proxy to the function, allowing
invocations to be made by passing in arguments, and invoking a
continuation in the main process when the function returns.
The object represents the function code itself, rather than one
specific invocation of it. It can be called multiple times, by the
"call" method. Multiple outstanding invocations can be called; they
will be dispatched in the order they were queued. If only one worker
process is used then results will be returned in the order they were
called. If multiple are used, then each request will be sent in the
order called, but timing differences between each worker may mean
results are returned in a different order.
Since the code block will be called multiple times within the same
child process, it must take care not to modify any of its state that
might affect subsequent calls. Since it executes in a child process, it
cannot make any modifications to the state of the parent program.
Therefore, all the data required to perform its task must be
represented in the call arguments, and all of the result must be
represented in the return values.
The Function object is implemented using an IO::Async::Routine with two
IO::Async::Channel objects to pass calls into and results out from it.
The "IO::Async" framework generally provides mechanisms for
multiplexing IO tasks between different handles, so there aren't many
occasions when such an asynchronous function is necessary. Two cases
where this does become useful are:
1. When a large amount of computationally-intensive work needs to be
performed (for example, the "is_prime" test in the example in the
"SYNOPSIS").
2. When a blocking OS syscall or library-level function needs to be
called, and no nonblocking or asynchronous version is supplied.
This is used by "IO::Async::Resolver".
This object is ideal for representing "pure" functions; that is, blocks
of code which have no stateful effect on the process, and whose result
depends only on the arguments passed in. For a more general co-routine
ability, see also IO::Async::Routine.
PARAMETERS
The following named parameters may be passed to "new" or "configure":
code => CODE
The body of the function to execute.
model => "spawn" | "thread"
Optional. Requests a specific "IO::Async::Routine" model. If
not supplied, leaves the default choice up to Routine.
min_workers => INT
max_workers => INT
The lower and upper bounds of worker processes to try to keep
running. The actual number running at any time will be kept
somewhere between these bounds according to load.
max_worker_calls => INT
Optional. If provided, stop a worker process after it has
processed this number of calls. (New workers may be started to
replace stopped ones, within the bounds given above).
idle_timeout => NUM
Optional. If provided, idle worker processes will be shut down
after this amount of time, if there are more than "min_workers"
of them.
exit_on_die => BOOL
Optional boolean, controls what happens after the "code" throws
an exception. If missing or false, the worker will continue
running to process more requests. If true, the worker will be
shut down. A new worker might be constructed by the "call"
method to replace it, if necessary.
setup => ARRAY
Optional array reference. Specifies the "setup" key to pass to
the underlying IO::Async::Process when setting up new worker
processes.
METHODS
$function->start
Start the worker processes
$function->stop
Stop the worker processes
$function->restart
Gracefully stop and restart all the worker processes.
$function->call( %params )
Schedules an invocation of the contained function to be executed on one
of the worker processes. If a non-busy worker is available now, it will
be called immediately. If not, it will be queued and sent to the next
free worker that becomes available.
The request will already have been serialised by the marshaller, so it
will be safe to modify any referenced data structures in the arguments
after this call returns.
The %params hash takes the following keys:
args => ARRAY
A reference to the array of arguments to pass to the code.
on_result => CODE
A continuation that is invoked when the code has been executed.
If the code returned normally, it is called as:
$on_result->( 'return', @values )
If the code threw an exception, or some other error occured
such as a closed connection or the process died, it is called
as:
$on_result->( 'error', $exception_name )
on_return => CODE and on_error => CODE
An alternative to "on_result". Two continuations to use in
either of the circumstances given above. They will be called
directly, without the leading 'return' or 'error' value.
$future = $function->call( %params )
When returning a future, the "on_result", "on_return" and "on_error"
continuations are optional.
$count = $function->workers
Returns the total number of worker processes available
$count = $function->workers_busy
Returns the number of worker processes that are currently busy
$count = $function->workers_idle
Returns the number of worker processes that are currently idle
NOTES
For the record, 123454321 is 11111 * 11111, a square number, and
therefore not prime.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.18.2 2014-05-14 IO::Async::Function(3)