93 lines
5.2 KiB
Go
93 lines
5.2 KiB
Go
/*
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Package tasklifecycle manages the execution order of tasks based on their
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lifecycle configuration. Its main structs are the Coordinator and the Gate.
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The Coordinator is used by an allocRunner to signal if a taskRunner is allowed
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to start or not. It does so using a set of Gates, each for a given task
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lifecycle configuration.
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The Gate provides a channel that can be used to block its listener on demand.
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This is done by calling the Open() and Close() methods in the Gate which will
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cause activate or deactivate a producer at the other end of the channel.
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The allocRunner feeds task state updates to the Coordinator that then uses this
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information to determine which Gates it should open or close. Each Gate is
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connected to a taskRunner with a matching lifecycle configuration.
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In the diagrams below, a solid line from a Gate indicates that it's open
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(active), while a dashed line indicates that it's closed (inactive). A
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taskRunner connected to an open Gate is allowed to run, while one that is
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connected to a closed Gate is blocked.
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The Open/Close control line represents the Coordinator calling the Open() and
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Close() methods of the Gates.
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In this state, the Coordinator is allowing prestart tasks to run, while
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blocking the main tasks.
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┌────────┐
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│ ALLOC │
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│ RUNNER │
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└───┬────┘
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│
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Task state
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│
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┌────────────▼────────────┐
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│Current state: │
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│Prestart │ ┌─────────────┐
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│ │ │ TASK RUNNER │
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│ ┌───────────────────┼─────────┤ (Prestart) │
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│ │ │ └─────────────┘
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│ │ │
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│ │ │ ┌─────────────┐
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│ │ COORDINATOR │ │ TASK RUNNER │
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│ │ ┌─ ─ ─┼─ ─ ─ ─┬╶┤ (Main) │
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│ │ ╷ │ ╷ └─────────────┘
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│ │ ╷ │ ╷
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│ │ ╷ │ ╷ ┌─────────────┐
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│ Prestart Main │ ╷ │ TASK RUNNER │
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└─────┬─┬───────────┬─┬───┘ └╶┤ (Main) │
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│ │Open/ ╷ │Open/ └─────────────┘
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│ │Close ╷ │Close
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┌──┴─▼─┐ ┌──┴─▼─┐
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│ GATE │ │ GATE │
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└──────┘ └──────┘
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When the prestart task completes, the allocRunner will send a new batch of task
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states to the Coordinator that will cause it to transition to a state where it
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will close the Gate for prestart tasks, blocking their execution, and will open
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the Gate for main tasks, allowing them to start.
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┌────────┐
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│ ALLOC │
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│ RUNNER │
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└───┬────┘
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│
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Task state
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│
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┌────────────▼────────────┐
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│Current state: │
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│Main │ ┌─────────────┐
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│ │ │ TASK RUNNER │
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│ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┼─ ─ ─ ─ ─┤ (Prestart) │
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│ ╷ │ └─────────────┘
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│ ╷ │
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│ ╷ │ ┌─────────────┐
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│ ╷ COORDINATOR │ │ TASK RUNNER │
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│ ╷ ┌─────┼───────┬─┤ (Main) │
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│ ╷ │ │ │ └─────────────┘
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│ ╷ │ │ │
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│ ╷ │ │ │ ┌─────────────┐
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│ Prestart Main │ │ │ TASK RUNNER │
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└─────┼─┬───────────┬─┬───┘ └─┤ (Main) │
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╷ │Open/ │ │Open/ └─────────────┘
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╷ │Close │ │Close
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┌──┴─▼─┐ ┌──┴─▼─┐
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│ GATE │ │ GATE │
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└──────┘ └──────┘
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Diagram source:
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https://asciiflow.com/#/share/eJyrVspLzE1VssorzcnRUcpJrEwtUrJSqo5RqohRsjI0MDTViVGqBDKNLA2ArJLUihIgJ0ZJAQYeTdmDB8XE5CGrVHD08fF3BjPRZYJC%2Ffxcg7DIEGk6VDWyUEhicbZCcUliSSp2hfgNR6BpxCmDmelcWlSUmlcCsdkKm62%2BiZmo7kEOCOK8jtVmrGZiMVchxDHYGzXEYSpIspVUpKAREOQaHOIYFKKpgGkvjcIDp8kk2t7zaEoDcWgCmsnO%2Fv5BLp5%2BjiH%2BQVhNbkKLjyY8LtNFAyDdCgoavo6efppQ0%2FDorkETrQGypxDtrxmkmEyiK8iJ24CiVGAeKyqBGgPNVWjmYk%2FrVE7X8LhBiwtEcQRSBcT%2B%2Bs4KyK5D4pOewlFMRglfuDy6vmkoLoaL1yDLwXUquDuGuCogq4aLYDd9CnbT0V2uVKtUCwCqNQgp)
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*/
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package tasklifecycle
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