SingletonLockScheduler

class beatdrop.schedulers.singleton_lock_scheduler.SingletonLockScheduler

Bases: Scheduler

Base singleton lock scheduler class.

This base class is used by scheduler where more that one can be started in parallel with run, but only one should be checking entries and sending them. Uses a lock based approach to stop/tell other schedulers from running and sending tasks.

Parameters:

  • max_interval (datetime.timedelta) – The maximum interval that the scheduler should sleep before waking up to check for due tasks.

  • sched_entry_types (Tuple[Type[ScheduleEntry]], default : (CrontabEntry, CrontabTZEntry, EventEntry, IntervalEntry)) – A list of valid schedule entry types for this scheduler. These are only stored in the scheduler, not externally.

  • default_sched_entries (List[ScheduleEntry], default : []) – Default list of schedule entries. In general these entries are not held in non-volatile storage so any metadata they hold will be lost if the scheduler fails. These entries are static. The keys cannot be overwritten or deleted.

  • lock_timeout (datetime.timedelta) – The time a scheduler does not refresh the scheduler lock before it is considered dead. Should be at least 3 times the max_interval.

delete(sched_entry: ScheduleEntry) → None

Delete a schedule entry from the scheduler.

Parameters:

sched_entry (ScheduleEntry) – Scheduler entry to delete from the scheduler.

Raises:

beatdrop.exceptions.MethodNotImplementedError – delete method not implemented.

get(key: str) → ScheduleEntry

Retrieve a schedule entry by its key.

Parameters:

key (str) – The schedule entry key.

Returns:

The schedule entry with the matching key.

Return type:

ScheduleEntry

Raises:

beatdrop.exceptions.MethodNotImplementedError – get method not implemented.

list() → Iterator[ScheduleEntry]

List schedule entries.

Returns:

List of schedule entries.

Return type:

Iterator[ScheduleEntry]

Raises:

beatdrop.exceptions.MethodNotImplementedError – list method not implemented.

run(max_iterations: int = None) → None

Run the scheduler.

Parameters:

max_iterations (int) –

default : None

The maximum number of iterations to run the scheduler. None is unlimited.

Raises:

beatdrop.exceptions.MethodNotImplementedError – Must implement run method.

save(sched_entry: ScheduleEntry, client_read_only: bool = False) → None

Save a new or update an existing schedule entry.

By default, read only attributes are not updated with save (suffixed with __).

Parameters:

  • sched_entry (ScheduleEntry) – Schedule entry to add or update in scheduler.

  • client_read_only (bool) – Overwrite client read only fields? False will not overwrite client read only fields. True will. This should almost always be False, unless you are a scheduler, or you know what you’re doing.

Raises:

beatdrop.exceptions.MethodNotImplementedError – save method not implemented.

send(sched_entry: ScheduleEntry) → None

Send a schedule entry to the task backend.

This should be used by the run method when a schedule is due. Subclasses can override this for common schedulers without changing the specifics of how a schedule runs. Send it to a queue, to celery etc.

NOTE: for the reasons above the send method should not perform any actions against the state of the scheduler or schedule entries.

Parameters:

sched_entry (ScheduleEntry) – Schedule entry that will be sent to the task backend.

Raises:

beatdrop.exceptions.MethodNotImplementedError – Must implement send method.