经常遇到MongoDB Perl驱动程序中的异常

Question

The web application is running but in my log error frequently run into this exceptions

can't get db response, not connected at ../MongoDB/Cursor.pm line 160.

invalid header received at ../MongoDB/Cursor.pm line 160.

can't locate object method "new" via package "MongoDB::Timestamp" at ../MongoDB/Collection.pm line 370.

Perl Driver

• MongoDB-0.702.2 ,

MongoDB server "version 2.4.8"

• 1 master
• 2 replication

MongoDB server status connection server sometime reach the limit connection

"connections" : {
        "current" : 20000,
        "available" : 0,
        "totalCreated" : NumberLong(73428104)
 },

Here my code for get connection from MongoDB

sub get_mongodb {
my ($self) = @_;

#master/slave
my $mode    = $self->mode;

#get db name
my $db      = $self->db;

my $obj = $self->{'o_mongodb_' . $mode . '_' . $db};

unless($obj) {
    my %opt;

    #result get_con
    #{
    #    'db'    => 'mongo',
    #    'host'  => [
    #            '10.10.10.1:27017',
    #            '10.10.10.2:27017',
    #            '10.10.10.3:27017'
    #       ]
    #}
    my $con = $self->get_con($db);

    if($mode eq 'master') {
        $opt{find_master} = 1;
    }
    else {
        $opt{find_master} = 0;
    }

    $opt{timeout}       = 50000;
    $opt{query_timeout} = -1;

    my @host    = @{$con->{host}};
    @host       = $self->{t}->util->shuffle(@host);
    $opt{host}  = 'mongodb://' . join(',', @host);

    my @opt = %opt;
    my $client;

    eval { 
        local $SIG{__DIE__}; 
        $client = MongoDB::MongoClient->new(@opt);
    };

    if(!$@) {
        $obj = $self->{'o_mongodb_' . $mode . '_' . $db} = $client->get_database($con->{db});
    }
    else {
        return 0;   
    }
}

if($mode eq 'master') {
    $MongoDB::Cursor::slave_okay = 0;
}
else {
    $MongoDB::Cursor::slave_okay = 1;   
}

return $obj;
}   

Is there something my code is wrong? Thanks for your time.

Answer 1

You are clearly running out of connections. The reason for this is clear from your comment, in that you are making a new connection with every request that results in hitting the database.

One thing you could try is to reduce the timeout value. This defaults to 20000ms and you are actually setting that higher. As a result connections are "hanging around", and with a busy server that is going to build up quickly.

A better strategy is to implement connection pooling. There is no default feature in the Perl driver, but there is a guide on the site that can give you some guidance on how to implement.

As an alternate to building that yourself you might want to look into MongoDBx::Class , which does have a connection pooling strategy.

The basic premise is that you do not want to be establishing a new connection for every request, but instead re-use from an available pool, of a set number, that will not allow your app to exhaust the available connections. You will also find that operation times are significantly faster, without the overhead of establishing a connection every time.

Answer 2

I have this problem too , check mongodb.log if you have many connection that don't close

https://jira.mongodb.org/browse/PERL-264