In order to be able to avoid a deadlock when CQL server cannot be started,
the view builder shutdown procedure is now split to two parts -
- drain and stop. Drain is performed before storage proxy shutdown,
but stop() will be called even before drain is scheduled.
The deadlock is as follows:
- view builder creates a reader permit in order to be able
to read from system tables
- CQL server fails to start, shutdown procedure begins
- view builder stop() is not called (because it was not scheduled
yet), so it holds onto its reader permit
- database shutdown procedure waits for all permits to be destroyed,
and it hangs indefinitely because view builder keeps holding
its permit.
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