Serializing code
(Data::Dump::Streamer)
Anton Berezin
tobez@tobez.org
Why serialize code?
To be able to specify now some code to execute later (possibly much later, in another process, on another machine) when a specific condition is met.
Callbacks on steroids
add_action(
condition => ...,
id => 42,
action => sub {
print "Condition is met!\n";
});
Callback conditions
-
mouse click;
button press;
"after $N milliseconds";
can read from $sock;
an $obj changed its state;
etc...
Serialized code conditions
As for callbacks, plus-
a DB row changed;
"after $N days";
a trouble ticket $ID resolved;
a CPE came online;
etc...
Serializing modules
-
Data::Dumper (or Data::Dump);
JSON (or JSON::Syck, or JSON::XS, or JSON::DWIW);
YAML (or YAML::Syck, or YAML::Tiny, or YAML::Whatever);
Storable;
other...
Most of them do not work for code, none of them works for closures.
Closures
if ($product->{state} eq "waiting") {
my $p_name = $product->{name};
my $p_id = $product->{id};
add_action(
condition => ...,
id => 42,
action => sub {
my $p = get_product($p_id);
$p->{state} = "ready";
$p->save_product;
print "$p_name is ready\n";
});
}
Data::Dump::Streamer
-
Data::Dump::Streamer
by Yves Orton
one of the more under-rated modules on CPAN
not unlike Data::Dumper
but designed for streaming
slower, more memory-efficient
handles closures
Data::Dump::Streamer example
my $id = 42;
my $name = "Larry Wall";
print Data::Dump::Streamer::Dump(sub {
print "My number is $id\n";
print "My name is $name (just kidding)\n";
})->Out();
Data::Dump::Streamer output
my ($id,$name);
$id = 42;
$name = 'Larry Wall';
$CODE1 = sub {
print "My number is $id\n";
print "My name is $name (just kidding)\n";
};
Dumped code evaluation
my $code = read_streamed_output(from => "somewhere");
my $CODE1 = undef;
eval $code;
unless ($@) {
$CODE1->();
}
Pitfalls: context
use WeirdModule; # imports &weird_function
store_code_in_the_db(sub {
weird_function(42);
});
$CODE1->();
Inside callbacks
-
require all needed modules;
use fully qualified subs;
use only simple vars from outside the sub;
do not ass-u-me
Thank you.
Thank you!
Any questions?