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34 lines
1.4 KiB
Markdown
34 lines
1.4 KiB
Markdown
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# Task specifications, task instances and task logs
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A *task specification* contains all information that is needed for computing
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the results of a task:
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- The function ID of the function that executes the task
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- The arguments (either object IDs for pass by reference
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or values for pass by value)
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- The IDs of the result objects
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From these, a task ID can be computed which is also stored in the task
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specification.
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A *task instance* represents one execution of a task specification.
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It consists of:
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- A scheduling state (WAITING, SCHEDULED, RUNNING, DONE)
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- The target node where the task is scheduled or executed
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- A unique task instance ID that identifies the particular execution
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of the task.
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The task data structures are defined in `common/task.h`.
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The *task log* is a mapping from the task instance ID to a sequence of
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updates to the status of the task instance. It is updated by various parts
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of the system:
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1. The local scheduler writes it with status WAITING when submits a task to the global scheduler
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2. The global scheduler appends an update WAITING -> SCHEDULED together with the node ID when assigning the task to a local scheduler
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3. The local scheduler appends an update SCHEDULED -> RUNNING when it assigns a task to a worker
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4. The local scheduler appends an update RUNNING -> DONE when the task finishes execution
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The task log is defined in `common/state/task_log.h`.
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