alter_job()

CommunityCommunity functions are available under Timescale Community Edition. Click to learn more.

Actions scheduled using the TimescaleDB automation framework run periodically in a background worker. You can change the schedule of these jobs with the alter_job function. To alter an existing job, refer to it by job_id. The job_id runs a given action, and its current schedule can be found in the timescaledb_information.jobs view, which lists information about every scheduled action, as well as in timescaledb_information.job_stats. The job_stats view also gives information about when each job was last run and other useful statistics for deciding what the new schedule should be.

Required arguments

Name	Type	Description
`job_id`	`INTEGER`	The ID of the policy job being modified

Optional arguments

Name	Type	Description
`schedule_interval`	`INTERVAL`	The interval at which the job runs. Defaults to 24 hours.
`max_runtime`	`INTERVAL`	The maximum amount of time the job is allowed to run by the background worker scheduler before it is stopped.
`max_retries`	`INTEGER`	The number of times the job is retried if it fails.
`retry_period`	`INTERVAL`	The amount of time the scheduler waits between retries of the job on failure.
`scheduled`	`BOOLEAN`	Set to `FALSE` to exclude this job from being run as background job.
`config`	`JSONB`	Job-specific configuration, passed to the function when it runs.
`next_start`	`TIMESTAMPTZ`	The next time at which to run the job. The job can be paused by setting this value to `infinity`, and restarted with a value of `now()`.
`if_exists`	`BOOLEAN`	Set to `true`to issue a notice instead of an error if the job does not exist. Defaults to false.
`check_config`	`REGPROC`	A function that takes a single argument, the `JSONB` `config` structure. The function is expected to raise an error if the configuration is not valid, and return nothing otherwise. Can be used to validate the configuration when updating a job. Only functions, not procedures, are allowed as values for `check_config`.
`fixed_schedule`	`BOOLEAN`	To enable fixed scheduled job runs, set to `TRUE`.
`initial_start`	`TIMESTAMPTZ`	Set the time when the `fixed_schedule` job run starts. For example, `19:10:25-07`.
`timezone`	`TEXT`	Address the 1-hour shift in start time when clocks change from Daylight Saving Time to Standard Time. For example, `America/Sao_Paulo`.

When a job begins, the next_start parameter is set to infinity. This prevents the job from attempting to be started again while it is running. When the job completes, whether or not the job is successful, the parameter is automatically updated to the next computed start time.

Note that altering the next_start value is only effective for the next execution of the job in case of fixed schedules. On the next execution, it will automatically return to the schedule.

Returns

Column	Type	Description
`job_id`	`INTEGER`	The ID of the job being modified
`schedule_interval`	`INTERVAL`	The interval at which the job runs. Defaults to 24 hours
`max_runtime`	`INTERVAL`	The maximum amount of time the job is allowed to run by the background worker scheduler before it is stopped
`max_retries`	INTEGER	The number of times the job is retried if it fails
`retry_period`	`INTERVAL`	The amount of time the scheduler waits between retries of the job on failure
`scheduled`	`BOOLEAN`	Returns `true` if the job is executed by the TimescaleDB scheduler
`config`	`JSONB`	Job-specific configuration, passed to the function when it runs
`next_start`	`TIMESTAMPTZ`	The next time to run the job
`check_config`	`TEXT`	The function used to validate updated job configurations

Sample usage

Reschedules job ID 1000 so that it runs every two days:


SELECT alter_job(1000, schedule_interval => INTERVAL '2 days');

Disables scheduling of the compression policy on the conditions hypertable:


SELECT alter_job(job_id, scheduled => false)
FROM timescaledb_information.jobs
WHERE proc_name = 'policy_compression' AND hypertable_name = 'conditions'

Reschedules continuous aggregate job ID 1000 so that it next runs at 9:00:00 on 15 March, 2020:


SELECT alter_job(1000, next_start => '2020-03-15 09:00:00.0+00');

Calculation of next start on failure

When a job run results in a runtime failure, the next start of the job is calculated taking into account both its retry_period and schedule_interval. The next_start time is calculated using the following formula:


next_start = finish_time + consecutive_failures * retry_period ± jitter

where jitter (± 13%) is added to avoid the "thundering herds" effect.

Note

To ensure that the next_start time is not put off indefinitely or produce timestamps so large they end up out of range, it is capped at 5schedule_interval. Also, more than 20 consecutive failures are not considered, so if the number of consecutive failures is higher, then it multiplies by 20.

Additionally, in the case of jobs with fixed schedules, the system ensures that if the next start calculated as specified, surpasses the next scheduled execution, then the job is executed again at the next scheduled slot and not after that. This ensures that the job does not miss scheduled executions.

Finally, there is a distinction between runtime failures that do not cause the job to crash and job crashes. In the event of a job crash, the next start calculation still follows the above formula, but it is always at least 5 minutes after the job's last finish, to give an operator enough time to disable it before another crash.