Scheduler Plugins¶
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class
distributed.diagnostics.plugin.
SchedulerPlugin
[source]¶ Interface to extend the Scheduler
The scheduler operates by triggering and responding to events like
task_finished
,update_graph
,task_erred
, etc..A plugin enables custom code to run at each of those same events. The scheduler will run the analogous methods on this class when each event is triggered. This runs user code within the scheduler thread that can perform arbitrary operations in synchrony with the scheduler itself.
Plugins are often used for diagnostics and measurement, but have full access to the scheduler and could in principle affect core scheduling.
To implement a plugin implement some of the methods of this class and add the plugin to the scheduler with
Scheduler.add_plugin(myplugin)
.Examples
>>> class Counter(SchedulerPlugin): ... def __init__(self): ... self.counter = 0 ... ... def transition(self, key, start, finish, *args, **kwargs): ... if start == 'processing' and finish == 'memory': ... self.counter += 1 ... ... def restart(self, scheduler): ... self.counter = 0
>>> c = Counter() >>> scheduler.add_plugin(c)
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transition
(key, start, finish, *args, **kwargs)[source]¶ Run whenever a task changes state
Parameters: key: string
start: string
Start state of the transition. One of released, waiting, processing, memory, error.
finish: string
Final state of the transition.
*args, **kwargs: More options passed when transitioning
This may include worker ID, compute time, etc.
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