Agreed but the problem with a daemon is you need to keep checking its running if it doesn't run then you have no checks, for a database with critical information this isnt viable, cron for all its problems is part of the os makeup and can be trusted to run things at a certain time.
In this case the person is doing a simple show status, if this takes more than a fraction of a minute then something is wrong. In general you wouldn't be monitoring more than once a minute because of timeouts etc.. A lockfile and check will surfice if it's a problem with running multiple instances (should it take over a minute). -----Original Message----- From: Chas Owens [mailto:[EMAIL PROTECTED] Sent: 08 August 2007 13:36 To: Andrew Curry Cc: [EMAIL PROTECTED]; beginners@perl.org Subject: Re: run perl as service On 8/8/07, Andrew Curry <[EMAIL PROTECTED]> wrote: > To be honest in terms of database monitoring cron is usually the way to go. > The advantage Is that then you don't need to monitor the monitoring program. > As a DBA you need reliable data in terms of status etc... You could > write an overcomplicated daemon which monitors its state but if cron > is an option its much simpler and less can go wrong. snip There are two downsides to cron: the finest resolution it can do is one minute and it doesn't prevent overlapping runs. Now, you can achieve sub minute timing by saying * * * * * foo.pl * * * * * sleep .25; foo.pl * * * * * sleep .5; foo.pl * * * * * sleep .75; foo.pl But this still doesn't prevent multiple concurrent runs of foo.pl. So now, we have to add code to foo.pl to stop it from doing anything if another copy is running (usually a lock file). But, if something goes wrong the other copies might never run again. We are now back in the same position as using a daemon, but without the benefits. Now, if you have access to a scheduler other than can handle these sorts of conditions (Control-M and CA Unicenter come to mind), then by all means use them, but cron is not always a good choice. That said, if you only need to run once per minute or less frequently and don't care if the programs overlap, cron works just fine (unless you have access to a better scheduler). This e-mail is from the PA Group. For more information, see www.thepagroup.com. This e-mail may contain confidential information. Only the addressee is permitted to read, copy, distribute or otherwise use this email or any attachments. If you have received it in error, please contact the sender immediately. Any opinion expressed in this e-mail is personal to the sender and may not reflect the opinion of the PA Group. Any e-mail reply to this address may be subject to interception or monitoring for operational reasons or for lawful business practices. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
