Stater is a library to help perform very long running tasks. It supports reboots, pausing, and resuming.
The library works by allowing you to define a IncrementalWorkFunction that performs the smallest amount of work possible, and then updating the Task's state. After each run of the IncrementalWorkFunction the task stores the state using your defined StorageDriver.
You can then pause and resume the task. If the program restarts, on the next start the task engine will recognize the abandoned tasks, and start them again.
The goal is to ultimately call
task := TaskEngine.NewTask(...)
task.Start(...)That function will start a task that will run (and resume across restarts).
To get there you must:
- Create some storage driver (where we will store the state)
- Define your work functions
- Create a task engine
Each step is relatively painless, but is necessary to start a task off of the engine.
The godoc has a full example of doing the above steps.
Below are some more instructions
The storage driver is a way to store/load the state of running tasks. You can create your own that obeys the StorageDriver interface, or just use the built in filedriver (see example in godoc).
A work function is the smallest amount of work possible towards the larger task. At the end, the function returns a new "state" that the next call of the function will continue from.
We define the work functions all at once to the task engine as a map. This means the task only needs to know the "name" of it's work function. We do this because we cannot save the work function to disk, we need to save a "reference/pointer" so we know what to run when the task starts again (especially across restarts).
To define your work functions simple create a map[string]stater.IncrementalWorkFunction{}
The task engine is the central location to store the StorageDriver and the Messager.
It also re-starts all stopped tasks if the program restarts.
To create it simply use the StorageDriver and workFunctions you have defined above (see godoc for details).
This library is early in development and will have bugs. I'm sure there are some interesting race conditions possible, but for simple usage it should hold up.