Controlling Start Times

In defining the time period for jobs, chains, and orders, you have a couple of choices. First, you can define a specific time slot in which a job can start – for example, a daily account reconciliation after all of the database imports for accounts receivable and accounts payable are completed. However, because of the load this job causes on the system, it should not start until after 11:00pm, even if the other jobs are completed.

The second way is to define a specific start time. For example, the account reconciliation should always start at 11:00pm, or you want the account reconciliation job to run repeatedly every 12 hours. Naturally, if you have a job chain in which the jobs need to be run sequentially, then hard start times of the individual jobs probably won't be needed. However, you can define an order that is started every day at 7:00am, which in turn starts a job chain.

Note that you are not just limited to running jobs at specific hours but can configure a job or order to run on specific days of the week or days of the month, or according to a more complex definition, such as the second Monday of the month, the third to last day of the month, and even days such as January 8 and February 16, but no other dates.

Specific start times for jobs and job chains are obviously a useful feature, but it is not always possible to know in advance when a job needs to be started (e.g., database imports that need to wait until a specific file is delivered). The more direct method is to write the job script in such a way that it exits if the file is not there. However, if your system is then loaded with unnecessary log entries and so forth, you can quickly lose sight of important events. To solve this problem, the Job Scheduler allows you to set up "watch directories." As the name implies, these are directories that are watched for specific files or even based on regular expressions (Figure 4).

Figure 4: Job Dependencies can be shown using the Job Chain Illustration.

Defining Your Own Next Order

After I got past preconceptions and misunderstandings resulting from my experience with other scheduling products, I became more and more fond of the Open Source Job Scheduler. When I got the hang of things, the product was actually easy to configure and administer.

My experience with SOS GmbH itself was extremely pleasant. From the receptionist, through tech support, and up to the managing director, everyone I talked to seemed to be convinced of the quality of the product and the company itself. I became impressed with the company after I identified a bug and the patched Java JAR file was on their server in less than a day!

Even with a small network, the Open Source Job Scheduler provides useful functionality. With larger installations, it is almost an indispensable tool.

The Author

James Mohr is responsible for the monitoring of several datacenters for a business solutions provider in Coburg, Germany. In addition to running the Linux Tutorial web site http://www.linux-tutorial.info, James is the author of several books and dozens of articles on a wide range of topics.