AppEngine object runtime behavior
- Last UpdatedJul 19, 2024
- 2 minute read
Runtime behavior pertains to the running state of a deployed AppEngine object. The most important function of the running AppEngine is its scheduler. The AppEngine has a scan-based scheduler that triggers at the configured scan period, specified in milliseconds. Each scan period interval, the AppEngine executes every object on the engine, include itself. The order that objects are executed is called the scheduler order, or process order. For more information on the process order, see Processing order for AppEngines.
Once deployed and operating, the AppEngine object can assume one of the following states:
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State Change |
Behavior |
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Startup |
In this transition state, the AppEngine object starts as a new operating system process and starts all of the objects that it hosts. Objects hosted by the AppEngine object are:
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Going onscan |
During this transition state, the AppEngine object places all of the objects that it hosts onscan, if their current commanded scan state is onscan. |
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Running onscan |
In this state, the AppEngine object schedules and executes all hosted objects that are onscan. Offscan hosted objects are not executed. In addition, the AppEngine object periodically saves each hosted object's data to checkpoint for future recovery. |
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Going offscan |
During this transition state, the AppEngine object places all of the objects that it hosts offscan (inoperative). When offscan, data quality within hosted objects is set to BAD. |
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Offscan |
The scheduler is idle and no objects are executed, but all objects and their attributes are available for read/write access. In addition, the AppEngine object periodically saves each hosted object's data to checkpoint for future recovery. |
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Shutdown |
In this state, the AppEngine object shuts down as an operating system process. Before doing so, one final checkpoint is performed just after all objects hosted by the AppEngine object are:
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