Re^7: Create parallel database handles... (MCE::Loop)

in reply to Re^6: Create parallel database handles... (MCE::Loop)
in thread Create parallel database handles or SQL statements for multi-threaded/process access to Postgres DB using DBI, DBD::Pg and Parallel::ForkManager

Greetings, perlygapes

The shared variable is constructed using OO, not via the TIE interface. Therefore, assigning to 0 overwrites the variable. Incrementing is possible via $process->incr. Another way is MCE->chunk_id (2nd example). MCE::Mutex is helpful for one worker to access a resource, blocking others (3rd example).

$process->incr()

#!/usr/bin/perl
use strict; use warnings; use 5.010;
use Data::Dumper; use HTTP::Tiny;
use Time::HiRes 'gettimeofday', 'tv_interval';
use MCE; use MCE::Shared;

my $ua   = HTTP::Tiny->new( timeout => 10 );
my @urls = qw< gap.com amazon.com ebay.com lego.com wunderground.com
    imdb.com underarmour.com disney.com espn.com dailymail.com >;

my $report  = MCE::Shared->hash;
my $process = MCE::Shared->scalar(0);

MCE->new( max_workers => 6 )->foreach( \@urls, sub {
    my $start = [gettimeofday];
    say $process->incr()."->GETting https://".$_;
    $ua->get('https://' . $_);
    $report->set( $_, tv_interval($start, [gettimeofday]) );
});

say Dumper $report->export;
[download]

MCE->chunk_id()

#!/usr/bin/perl
use strict; use warnings; use 5.010;
use Data::Dumper; use HTTP::Tiny;
use Time::HiRes 'gettimeofday', 'tv_interval';
use MCE; use MCE::Shared;

my $ua   = HTTP::Tiny->new( timeout => 10 );
my @urls = qw< gap.com amazon.com ebay.com lego.com wunderground.com
    imdb.com underarmour.com disney.com espn.com dailymail.com >;

my $report = MCE::Shared->hash;

MCE->new( max_workers => 6 )->foreach( \@urls, sub {
    my $start = [gettimeofday];
    say MCE->chunk_id()."->GETting https://".$_;
    $ua->get('https://' . $_);
    $report->set( $_, tv_interval($start, [gettimeofday]) );
});

say Dumper $report->export;
[download]

Assessing 3rd DB -- one worker

use strict; use warnings; use 5.010;
use Data::Dumper; use HTTP::Tiny;
use Time::HiRes 'gettimeofday', 'tv_interval';
use MCE; use MCE::Shared; use MCE::Mutex;

my $ua   = HTTP::Tiny->new( timeout => 10 );
my @urls = qw< gap.com amazon.com ebay.com lego.com wunderground.com
    imdb.com underarmour.com disney.com espn.com dailymail.com >;

my $report = MCE::Shared->hash;
my $mutex  = MCE::Mutex->new();

MCE->new( max_workers => 6 )->foreach( \@urls, sub {
    my $start = [gettimeofday];
    say MCE->chunk_id()."->GETting https://".$_;
    $ua->get('https://' . $_);
    $report->set( $_, tv_interval($start, [gettimeofday]) );

    # access 3rd DB, one worker
    $mutex->lock;
    # update ...
    $mutex->unlock;

    # ditto
    $mutex->enter( sub {
        # update ...
    });
});

say Dumper $report->export;
[download]

Regards, Mario

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