4J

While working on Hadoop, I found that connecting to a DB to get or insert data presented a problem as you often need more connections then what's available. My solution right now is to "wait" for a connection to become available - without using any fancy queuing mechanisms:

# Connect to DB
my $cont   = 0;
my $tries  = 0;
my $dbh1;
while( not $cont ) {

       $tries++;
       eval {
                      
               $dbh1 = DBI->connect( "dbi:mysql:database=$dbdb;host=$dbhost;port=$dbport", "$dbuser", "$dbpass" );

       };

       if( $@ ) { sleep( 1 ); } else { $cont++; }

       if( $tries > 3600 ) {
      
               # We have been trying for an hour - give up
               print "GIVE_UP\t1\n";
               exit;
                      
       }

}

And that's it. When the while loop finally exists, you have a DB handle to use. In the above example we retry for more then an hour - which should be sufficient for most scenarios.

Hope some one else find it useful as well.

Labels: database, hadoop, mysql, perl