Gossamer Forum: General: Perl Programming: eval and db failover

Dec 3, 2003, 2:14 AM

robyone

User (119 posts)

Dec 3, 2003, 2:14 AM

Post #1 of 7

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eval and db failover

Hi. I put this perl code in my application in order to switch automatically to the backup server if the primary server is down.

I found that the backup ip has been used many times even, if the primary was up and running Crazy

Can you evaluate this and let me know your ideas and/or experience in similar situations?

Code:
  
eval {   
  
$db='DBI:mysql:database='.$db_name.';hostname='.$db_host;  
  
my $dbh = DBI->connect($db,$db_user, $db_pass);   
  
$dbh->disconnect;  
  
};  
  
if ($@) {  
  
$db_host ="192.168.1.21";

...

Dec 3, 2003, 2:24 AM

Andy

Veteran / Moderator (18441 posts)

Dec 3, 2003, 2:24 AM

Post #2 of 7

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Re: [robyone] eval and db failover In reply to

That should be ok. If you are using strict though, you may need to define the 'my' variables outside the eval { } part.

Other than that, it should work fine :)

Cheers

Andy (mod)
andy@ultranerds.co.uk

Dec 3, 2003, 2:35 AM

robyone

User (119 posts)

Dec 3, 2003, 2:35 AM

Post #3 of 7

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Re: [Andy] eval and db failover In reply to

Hi. Thanks for your reply.

Do you mean .. not sure it works.

Why it is failing sometimes only? A delay on the connection?

Code:

my $db_host ="192.168.1.20"; 

eval {    
   
$db='DBI:mysql:database='.$db_name.';hostname='.$db_host;   
   
my $dbh = DBI->connect($db,$db_user, $db_pass);    
   
$dbh->disconnect;   
   
};   
   
if ($@) {   
   
my $db_host ="192.168.1.21";   
   
...

Dec 3, 2003, 2:45 AM

Andy

Veteran / Moderator (18441 posts)

Dec 3, 2003, 2:45 AM

Post #4 of 7

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Re: [robyone] eval and db failover In reply to

Not sure. You could try;

Code:
my $db_host ="192.168.1.20";  

my $db = 'DBI:mysql:database='.$db_name.';hostname='.$db_host; 
my $backup_db = 'DBI:mysql:database='.$db_name.';hostname=192.168.1.21'; 

my $dbh = DBI->connect($db,$db_user, $db_pass) ||  DBI->connect($backup_db,$db_user, $db_pass);       

$dbh->disconnect;

Untested, so it may not work.

Cheers

Andy (mod)
andy@ultranerds.co.uk