Aijaz Ansari > TaskForest-1.09 > TaskForest

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Module Version: 1.09   Source   Latest Release: TaskForest-1.37

NAME ^

TaskForest - Simple, powerful task scheduler

SYNOPSIS ^

  # Run the main program, checking for jobs to run.
  # By default, this will run until 23:55
  #
  use TaskForest;
  my $task_forest = TaskForest->new();
  $task_forest->runMainLoop();

  OR

  # Display the current status of all jobs scheduled to run today
  #
  use TaskForest;
  my $task_forest = TaskForest->new();
  $task_forest->status();

  # Rerun job J_RESOLVE in family F_DNS
  use TaskForest::Rerun;
  rerun("F_DNS", "J_RESOLVE", $log_dir);
    
  # Rerun job J_RESOLVE in family F_DNS
  use TaskForest::Rerun;
  &TaskForest::Rerun::rerun("F_DNS", "J_RESOLVE", $log_dir);
    
  # Mark job J_RESOLVE in family F_DNS as Success
  use TaskForest::Mark;
  &TaskForest::Mark::mark("F_DNS", "J_RESOLVE", $log_dir, "Success");

DESCRIPTION ^

The TaskForest Job Scheduler (TF) is a simple but expressive job scheduling system. A job is defined as any executable program that resides on the file system. Jobs can depend on each other. Jobs can also have start times before which a job may not by run. Jobs can be grouped together into "Families." A family has a start time associated with it before which none of its jobs may run. A family also has a list of days-of-the-week associated with it. Jobs within a family may only run on these days of the week.

Jobs and families are given simple names. A family is described in a family file whose name is the family name. Each family file is a text file that contains 1 or more job names. The layout of the job names within a family file determine the dependencies between the jobs (if any).

Family names and job names should contain only the characters shown below: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_

Let's see a few examples. In these examples the dashes (-), pipes (|) and line numbers are not parts of the files. They're only there for illustration purposes. The main script expects environment variables or command line options that specify the locations of the directory that contain family files, the directory that contains job files, and the directory where the logs will be written. The directory that contains family files should contain only family files.

EXAMPLE 1 - Family file named F_ADMIN

    +---------------------------------------------------------------------
 01 |start => '02:00', tz => 'America/Chicago', days => 'Mon,Wed,Fri'
 02 |
 03 | J_ROTATE_LOGS()
 04 |
    +---------------------------------------------------------------------

The first line in any family file always contains 3 bits of information about the family: the start time, the time zone, and the days on which this jobs in this family are run.

In this case, this family starts at 2:00 a.m. Chicago time. The time is adjusted for daylight savings time. This family 'runs' on Monday, Wednesday and Friday only. Pay attention to the format: it's important.

Valid days are 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'. Days must be separated by commas.

All start times (for families and jobs) are in 24-hour format. '00:00' is midnight, '12:00' is noon, '13:00' is 1:00 p.m. and '23:59' is one minute before midnight.

There is only one job in this family - J_ROTATE_LOGS. This family will start at 2:00 a.m., at which time J_ROTATE_LOGS will immediately be run. Note the empty parentheses [()]. These are required.

What does it mean to say that J_ROTATE_LOGS will be run? It means that the system will look for a file called J_ROTATE_LOGS in the directory that contains job files. That file should be executable. The system will execute that file (run that job) and keep track of whether it succeeded or failed. The J_ROTATE_LOGS script can be any executable file: a shell script, a perl script, a C program etc.

To run the program, the system actually runs a wrapper script that invokes the job script. The location of the wrapper script is specified on the command line or in an environment variable.

Now, let's look at a slightly more complicated example:

EXAMPLE 2 - Job Dependencies

This family file is named WEB_ADMIN

    +---------------------------------------------------------------------
 01 |start => '02:00', tz => 'America/Chicago', days => 'Mon,Wed,Fri'
 02 |
 03 |               J_ROTATE_LOGS()
 04 |
 05 | J_RESOLVE_DNS()               Delete_Logs_Older_Than_A_Year()
 06 |
 07 |               J_WEB_REPORTS()      
 08 |
 09 |            J_EMAIL_WEB_RPT_DONE()  # send me a notification
 10 |
    +---------------------------------------------------------------------

A few things to point out here: - Blank lines are ignored. - A hash (#) and anything after it, until the end of the line is treated as a comment and ignored - Job and family names do not have to start with J_ or be in upper case.

Now then, all jobs on a single line are started AT THE SAME TIME. All jobs on a line are started only when all jobs on the previous line are executed successfully. If there are no jobs on a previous line (as in the case of line 3 above), all jobs on that line are started when the family starts (2:00 a.m. above). There is an exception to this rule that we'll see in the next example.

So the above family can be interpreted in English as follows: "All WEB_ADMIN jobs are eligible to run after 2:00 a.m Chicago time on Mondays, Wedesdays and Fridays. The first job to be run is J_ROTATE_LOGS. If that succeeds, then J_RESOLVE_DNS and Delete_Logs_Older_Than_A_Year are started at the same time. If both these jobs succeed, then J_WEB_REPORTS is run. If that job succeeds, the J_EMAIL_WEB_RPT_done is run."

EXAMPLE 3 - TIME DEPENDENCIES

Let's say tha twe don't want J_RESOLVE_DNS to start before 9:00 a.m. because it's very IO-intensive and we want to wait until the relatively quiet time of 9:00 a.m. In that case, we can put a time dependency of the job. This adds a restriction to the job, saying that it may not run before the time specified. We would do this as follows:

    +---------------------------------------------------------------------
 01 |start => '02:00', tz => 'America/Chicago', days => 'Mon,Wed,Fri'
 02 |
 03 |               J_ROTATE_LOGS()
 04 |
 05 | J_RESOLVE_DNS(start => '09:00')    Delete_Logs_Older_Than_A_Year()
 06 |
 07 |               J_WEB_REPORTS()      
 08 |
 09 |            J_EMAIL_WEB_RPT_DONE()  # send me a notification
 10 |
    +---------------------------------------------------------------------

J_ROTATE_LOGS will still start at 2:00, as always. As soon as it succeeds, Delete_Logs_Older_Than_A_Year is started. If J_ROTATE_LOGS succeeds before 09:00, the system will wait until 09:00 before starting J_RESOLVE_DNS. It is possible that Delete_Logs_Older_Than_A_Year would have started and complete by then. J_WEB_REPORTS would not have started in that case, because it is dependent on two jobs, and both of them have to run successfully before it can run.

For completeness, you may also specify a timezone for a job's time dependency as follows:

 05 | J_RESOLVE_DNS(start=>'10:00', tz=>'America/New_York')  Delete_Logs_Older_Than_A_Year()

EXAMPLE 4 - JOB FORESTS

You can see in the example above that line 03 is the start of a group of dependent job. No job on any other line can start unless the job on line 03 succeeds. What if you wanted two or more groups of jobs in the same family that start at the same time (barring any time dependencies) and proceed independently of each other?

To do this you would separate the groups with a line containing one or more dashes (only). Consider the following family:

    +---------------------------------------------------------------------
 01 |start => '02:00', tz => 'America/Chicago', days => 'Mon,Wed,Fri'
 02 |
 03 |               J_ROTATE_LOGS()
 04 |
 05 | J_RESOLVE_DNS(start => '09:00')    Delete_Logs_Older_Than_A_Year()
 06 |
 07 |               J_WEB_REPORTS()      
 08 |
 09 |            J_EMAIL_WEB_RPT_DONE()  # send me a notification
 10 |
 11 |----------------------------------------------------------------------
 12 |
 13 | J_UPDATE_ACCOUNTS_RECEIVABLE()
 14 |
 15 | J_ATTEMPT_CREDIT_CARD_PAYMENTS()
 16 |
 17 |----------------------------------------------------------------------
 18 |
 19 | J_SEND_EXPIRING_CARDS_EMAIL()
 20 |
    +---------------------------------------------------------------------

Because of the lines of dashes on lines 11 and 17, the jobs on lines 03, 13 and 19 will all start at 02:00. These jobs are independent of each other. J_ATTEMPT_CREDIT_CARD_PAYMENT will not run if J_UPDATE_ACCOUNTS_RECEIVABLE fails. That failure, however will not prevent J_SEND_EXPIRING_CARDS_EMAIL from running.

Finally, you can specify a job to run repeatedly every 'n' minutes, as follows:

    +---------------------------------------------------------------------
 01 |start => '02:00', tz => 'America/Chicago', days => 'Mon,Wed,Fri'
 02 |
 03 | J_CHECK_DISK_USAGE(every=>'30', until=>'23:00')
 04 |
    +---------------------------------------------------------------------

This means that J_CHECK_DISK_USAGE will be called every 30 minutes and will not run on or after 23:00. By default, the 'until' time is 23:59. If the job starts at 02:00 and takes 25 minutes to run to completion, the next occurance will still start at 02:30, and not at 02:55. By default, every repeat occurrance will only have one dependency - the time - and will not depend on earlier occurances running successfully or even running at all. If line 03 were:

 03 | J_CHECK_DISK_USAGE(every=>'30', until=>'23:00', chained=>1)

...then each repeat job will be dependent on the previous occurance.

USAGE ^

There are a few simple scripts in the bin directory that simplify usage. To run the program you must let it know where it can find the necessary files and directories. This can be done by environment variables, or via the command line:

  export TF_JOB_DIR=/foo/jobs
  export TF_LOG_DIR=/foo/logs
  export TF_FAMILY_DIR=/foo/families
  export TF_RUN_WRAPPER=/foo/bin/run
  taskforest

  OR

  taskforest -run_wrapper=/foo/bin/run \
    --log_dir=/foo/logs \
    --job_dir=/foo/jobs \
    --family_dir=/foo/families

All jobs will run as the user who invoked taskforest.

You can rerun jobs or mark jobs as Success or Failure using the 'rerun' and 'mark' commands as shown below.

OPTIONS ^

The following command line options are required. If they are not specified on the command line, the environment will be searched for corresponding environment variables.

 --run_wrapper=/a/b/r  [or environment variable TF_RUN_WRAPPER]

   This is the location of the run wrapper that is used to execute the
   job files.  The run wrapper is also responsible for creating the
   semaphore files that denote whether a job ran successfully or not.
   You can use the provided run wrapper (bin/run).  If you need more
   functionality, like logging status to a database, you can create
   your own run wrapper, as long as it preserves the functionality of
   the default run_wrapper.   

 --log_dir=/a/b/l  [or environment variable TF_LOG_DIR]

   This is called the root log directory.  Every day a dated directory
   named in the form YYYYMMDD will be created and the semaphore files
   will be created in that directory.

 --job_dir=/a/b/j  [or environment variable TF_JOB_DIR]

   This is the location of all the job files.  Each job file should be
   an executable file (e.g.: a binary file, a shell script, a perl or
   python script).  The file names are used as job names in the family
   configuration files.  Job names may only contain the characters
   a-z, A-Z, 0-9 and _.  You may create aliases to jobs within this
   directory.

   If a job J1 is present in a family config file, any other
   occurrance of J1 in that family refers TO THAT SAME JOB INSTANCE.
   It does not mean that the job will be run twice.

   If you want the same job running twice, you will have to put it in
   different families, or make soft links to it and have the soft
   link(s) in the family file along with the actual file name.

   If a job is to run repeatedly every x minutes, you could specify
   that using the 'repeat/every' syntax shown above.

 --family_dir=/a/b/f  [or environment variable TF_FAMILY_DIR]

   This is the location of all the family files.  As is the case with
   jobs, family names are the file names.  Family names may only
   contain the characters a-z, A-Z, 0-9 and _.

The following command line options are optional

 --once_only

   If this option is set, the system will check each family once, run
   any jobs in the Ready state and then exit.  This is useful for
   testing, or if you want to invoke the program via cron or some
   similar system, or if you just want the program to run on demand,
   and not run and sleep all day.

 --end_time=HH:MM

   If once_only is not set, this option determines when the main
   program loop should end.  This refers to the local time in 24-hour
   format.  By default it is set to 23:55.  This is the recommended
   maximum.

 --wait_time

   This is the amount of seconds to sleep at the end of every loop.

 --verbose

   Print a lot of debugging information

 --help

   Display help text

DISPLAY STATUS ^

To get the status of all currently running and recently run jobs, enter the following command:

  status

  OR

  status --log_dir=/foo/logs --family_dir=/foo/families

  OR

  status --log_dir=/foo/logs --family_dir=/foo/families --collapse

If the --collapse option is used then pending repeat jobs will not be displayed.

RERUN A JOB ^

To rerun a job, enter the following command:

 rerun --log_dir=l_d --job=Ff::Jj 

where l_d is the log directory and Ff is the family name and Jj is the job name.

MARK A JOB SUCCESS OR FAILURE ^

To mark a previously-run job as success or failure, enter the following command:

 mark --log_dir=l_d --job=Ff::Jj --status=s

where l_d is the log directory and Ff is the family name, Jj is the job name, and s is 'Success' or 'Failure'.

BUGS ^

For an up-to-date bug listing and to submit a bug report, please visit our website at http://sourceforge.net/projects/taskforest/

SUPPORT ^

For support, please visit our website at http://sourceforge.net/projects/taskforest/

AUTHOR ^

Aijaz A. Ansari http://sourceforge.net/projects/taskforest/

If you're using this program, I would love to hear from you. Please visit our project website and let me know what you think of it.

COPYRIGHT ^

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself - specifically, the Artistic License.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO ^

perl(1).

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