Jobs

A job consists of a name, a node/node pool, a list of actions, a schedule, and an optional cleanup action. They are periodic events that do not interact with other jobs while running.

If all actions exit with status 0, the job has succeeded. If any action exists with a nonzero status, the job has failed.

Required Fields

name
Name of the job. Used in tronview and tronctl.
node
Reference to the node or pool to run the job in. If a pool, the job is run in a random node in the pool.
schedule
When to run this job. Schedule fields can take multiple forms. See Scheduling.
actions
List of actions.

Optional Fields

queueing (default True)
If a job run is still running when the next job run is to be scheduled, add the next run to a queue if this is True. Otherwise, cancel the job run. Note that if the scheduler used for this job is not defined to queue overlapping then this setting is ignored. The ConstantScheduler will not queue overlapping.
allow_overlap (default False)
If True new job runs will start even if the previous run is still running. By default new job runs are either cancelled or queued (see queuing).
run_limit (default 50)
Number of runs which will be stored. Once a Job has more then run_limit runs, the output and state for the oldest run are removed. Failed runs will not be removed.
all_nodes (default False)

If True run this job on each node in the node pool list. If a node appears more than once in the list, the job will be run on that node once for each appearance.

If False run this job on a random node from the node pool list. If a node appears more than once in the list, the job will be more likely to run on that node, proportionate to the number of appearances.

If node is not a node pool, this option has no effect.

cleanup_action
Action to run when either all actions have succeeded or the job has failed. See Cleanup Actions.
enabled (default True)
If False the job will not be scheduled to run. This configuration option is only relevant when a Job is first added to the configuration, after which this value will be ignored.
max_runtime (defailt None)

A time interval (ex: “2 hours”) that limits the duration of each job run. If the job run is still running after this duration, all of it’s actions are sent SIGTERM.

Note: This requires an Action Runners to be configured. If action_runner is none max_runtime does nothing.

Actions

Actions consist primarily of a name and command. An action’s command is executed as soon as its dependencies (specified by requires) are satisfied. So if your job has 10 actions, 1 of which depends on the other 9, then Tron will launch the first 9 actions in parallel and run the last one when all have completed successfully.

If any action exits with nonzero status, the job will continue to run any actions which do not depend on the failed action.

Required Fields

name
Name of the action. Used in tronview and tronctl.
command
Command to run on the specified node. A common mistake here is to use shell expansions or expressions in your command. Commands are run using exec so bash (or other shell) expressions will not work, and could cause the job to fail.

Optional Fields

requires
List of action names that must complete successfully before this action is run. Actions can only require actions in the same job.
node
Node or node pool to run the action on if different from the rest of the job.

Example Actions

jobs:
    - name: convert_logs
      node: node1
      schedule:
        start_time: 04:00:00
      actions:
        - name: verify_logs_present
          command: "ls /var/log/app/log_%(shortdate-1).txt"
        - name: convert_logs
          command: "convert_logs /var/log/app/log_%(shortdate-1).txt /var/log/app_converted/log_%(shortdate-1).txt"
          requires: [verify_logs_present]

Scheduling

Tron supports four methods for configuring the schedule of a job. Schedulers support a jitter parameter that allows them to vary their runtime by a random time delta.

Interval

Run the job every X seconds, minutes, hours, or days. The time expression is <interval> days|hours|minutes|seconds, where the units can be abbreviated.

Short form:

schedule: "interval 20s"

Long form:

schedule:
    type:   "interval"
    value:  "5 mins"
    jitter: "10 seconds"        # Optional

With alias:

schedule:
    type:   "interval"
    value:  "hourly"

Daily

Run the job on specific days at a specific time. The time expression is HH:MM:SS[ MTWRFSU].

Short form:

schedule: "daily 04:00:00"

Short form with days:

schedule: "daily 04:00:00 MWF"

Long form:

schedule:
    type:   "daily"
    value:  "07:00:00 MWF"
    jitter: "10 min"            # Optional

Cron

Schedule a job using cron syntax. Tron supports predefined schedules, ranges, and lists for each field. It supports the L in day of month field only (which schedules the job on the last day of the month). Only one of the day fields (day of month and day of week) can have a value.

Short form:

schedule: "cron */5 * * 7,8 *"  # Every 5 minutes in July and August
schedule: "cron 0 3-6 * * *"    # Every hour between 3am and 6am

Long form:

schedule:                       # long form
    type: "cron"
    value: "30 4 L * *"         # The last day of the month at 4:30am

Complex

More powerful version of the daily scheduler based on the one used by Google App Engine’s cron library. To use this scheduler, use a string in this format as the schedule:

("every"|ordinal) (days) ["of|in" (monthspec)] (["at"] HH:MM)
ordinal
Comma-separated list of 1st and so forth. Use every if you don’t want to limit by day of the month.
days
Comma-separated list of days of the week (for example, mon, tuesday, with both short and long forms being accepted); every day is equivalent to every mon,tue,wed,thu,fri,sat,sun
monthspec
Comma-separated list of month names (for example, jan, march, sep). If omitted, implies every month. You can also say month to mean every month, as in 1,8th,15,22nd of month 09:00.
HH:MM
Time of day in 24 hour time.

Some examples:

2nd,third mon,wed,thu of march 17:00
every monday at 09:00
1st monday of sep,oct,nov at 17:00
every day of oct at 00:00

In the config:

schedule: "every monday at 09:00"
schedule:
    type: "groc daily"
    value: "every day 11:22"
    jitter: "5 min"

Notes on Daylight Saving Time

Some system clocks are configured to track local time and may observe daylight savings time. For example, on November 6, 2011, 1 AM occurred twice. Prior to version 0.2.9, this would cause Tron to schedule a daily midnight job to be run an hour early on November 7, at 11 PM. For some jobs this doesn’t matter, but for jobs that depend on the availability of data for a day, it can cause a failure.

Similarly, some jobs on March 14, 2011 were scheduled an hour late.

To avoid this problem, set the Time Zone config variable. For example:

time_zone: US/Pacific

If a job is scheduled at a time that occurs twice, such as 1 AM on “fall back”, it will be run on the first occurrence of that time.

If a job is scheduled at a time that does not exists, such as 2 AM on “spring forward”, it will be run an hour later in the “new” time, in this case 3 AM. In the “old” time this is 2 AM, so from the perspective of previous jobs, it runs at the correct time.

In general, Tron tries to schedule a job as soon as is correct, and no sooner. A job that is schedule for 2:30 AM will not run at 3 AM on “spring forward” because that would be half an hour too soon from a pre-switch perspective (2 AM).

Note

If you experience unexpected scheduler behavior, file an issue on Tron’s Github page.

Cleanup Actions

Cleanup actions run after the job succeeds or fails. They are specified just like regular actions except that there is only one per job and it has no name or requirements list.

If your job creates shared resources that should be destroyed after a run regardless of success or failure, such as intermedmiate files or Amazon Elastic MapReduce job flows, you can use cleanup actions to tear them down.

The command context variable cleanup_job_status is provided to cleanup actions and has a value of SUCCESS or FAILURE depending on the job’s final state. For example:

-
    # ...
    cleanup_action:
      command: "python -m mrjob.tools.emr.job_flow_pool --terminate MY_POOL"

States

The following are the possible states for a Job and Job Run.

Job States

ENABLED
A run is scheduled and new runs will continue to be scheduled.
DISABLED
No new runs will be scheduled, and scheduled runs will be cancelled.
RUNNING
Job run currently in progress.

Job Run States

SCHE
The run is scheduled for a specific time
RUNN
The run is currently running
SUCC
The run completed successfully
FAIL
The run failed
QUE
The run is queued behind another run(s) and will start when said runs finish
CANC
The run was scheduled, but later cancelled.
UNKWN
The run is in and unknown state. This state occurs when tron restores a job that was running at the time of shutdown.

Action States

Job states are derived from the aggregate state of their actions. The following is a state diagram for an action.

_images/action.png