Introduce session worker threads. #4702
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This decouples request execution from IO threads, resolving several pesky NDP deadlock issues, as well as opening up doors for performance improvements where IO threads can focus on request deserialization, and worker threads focus on query execution. This design uses one thread per session started, under the assumption that the average database will deal with <= 10 000 live sessions per database instance. This should resolve deadlock issues seen on single-cpu systems.
| @@ -50,6 +51,12 @@ public JobHandle schedule( Group group, Runnable job ) | |||
| } | |||
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| @Override | |||
| public JobHandle schedule( Group group, Runnable job, Map<String,String> metadata ) | |||
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How about make schedule( Group, Runnable ) to invoke this one with NO_METADATA?
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This decouples request execution from IO threads, resolving several pesky NDP
deadlock issues, as well as opening up doors for performance improvements where
IO threads can focus on request deserialization, and worker threads focus on
query execution.
This design uses one thread per session started, under the assumption that the
average database will deal with <= 10 000 live sessions per database instance.
This should resolve deadlock issues seen on single-cpu systems.
Also, modify JobScheduler to allow dynamically created thread groups, and per-group thread creation strategies.