How to reconnect a dead DBD::Sybase Connection

[jfroebe]

Category:

DBI Related

Description:

It is important to know that this is just one method of reconnecting a dead connection.  Note that we are handling the errors manually for the individual query.  It wouldn't take much to create a db_exec subroutine so we just call the db_exec() subroutine and just worry about the reconnect in one place.

Notice that because of DBD::Sybase bug # 616, the error 151 will be printed to STDERR.

./test_sybase
OpenClient message: LAYER = (1) ORIGIN = (1) SEVERITY = (1) NUMBER = (
+151)
Message String: ct_cancel(): user api layer: external error: A connect
+ion to the server must exist on the connection structure before this 
+routine can be called.

ERROR: Connection to DBMS died

syb_db_disconnect(): ct_close() failed

MSG: Reconnected

#!/usr/bin/perl

use strict;
use warnings;

use lib "/home/jfroebe/lib";

use DBI;
use File::Basename;

our $SYBDBA1_login = 'login';
our $SYBDBA1_password = 'password';

our $dbh = connect_dbms();

sub report_err {
  my $msg = shift;
  my $type = shift;

  if ($type eq 'error') {
    print "ERROR: $msg\n";
  } else {
    print "MSG: $msg\n";
  }
}

sub exit_on_error {
  my $msg = shift;

  report_err($msg, "error");
  return -1;
}

sub connect_dbms {
  my $loc_dbh;
  my $script = basename($0);

 if ($loc_dbh = DBI->connect("dbi:Sybase:server=SISDBA1;loginTimeout=1
+0;timeout=30;scriptName=$script;encryptPassword=1;tdsLevel=CS_TDS_50;
+charset=iso_1", $SYBDBA1_login, $SYBDBA1_password, { PrintError => 0,
+ RaiseError => 1 } )) {
  return $loc_dbh;
 }

 report_err("unable to connect to SISDBA1", "error");
 return;
}

sub syb_loop {
  my $query = "exec sp_helpdb";


  RETRY: for (my $i = 0; $i < 10000; $i++) {
    my $array_ref;

    eval {
      $array_ref = $dbh->selectall_arrayref($query);
    };

    if ($@) {
      if ($dbh->err == 151 || $dbh->err == 60) {
        report_err("Connection to DBMS died", "error");
        undef($dbh);

        for (my $i = 0; $i < 10; $i++) {
          if( $dbh = connect_dbms() ) {
            report_err("Reconnected", "msg");
            redo RETRY;
          }
          sleep 3;
        }
        exit_on_error("Unable to reconnect after $i attempts!");
      }
    }
  }
}

syb_loop();