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

by marioroy (Parson)
on Aug 07, 2020 at 17:07 UTC ( #11120474=note: print w/replies, xml ) Need Help??


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;

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;

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;

Regards, Mario

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