"
The close path of the multishard combining reader is riddled with
workarounds the fact that the flat mutation reader couldn't wait on
futures when destroyed. Now that we have a close() method that can do
just that, all these workarounds can be removed.
Even more workarounds can be found in tests, where resources like the
reader concurrency semaphore are created separately for each tested
multishard reader and then destroyed after it doesn't need it, so we had
to come up with all sorts of creative and ugly workarounds to keep
these alive until background cleanup is finished.
This series fixes all this. Now, after calling close on the multishard
reader, all resources it used, including the life-cycle policy, the
semaphores created by it can be safely destroyed. This greatly
simplifies the handling of the multishard reader, and makes it much
easier to reason about life-cycle dependencies.
Tests: unit(dev, release:v2, debug:v2,
mutation_reader_test:debug -t test_multishard,
multishard_mutation_query_test:debug,
multishard_combining_reader_as_mutation_source:debug)
"
* 'multishard-combining-reader-close-cleanup/v3' of https://github.com/denesb/scylla:
mutation_reader: reader_lifecycle_policy: remove convenience methods
mutation_reader: multishard_combining_reader: store shard_reader via unique ptr
test/lib/reader_lifecycle_policy: destroy_reader: cleanup context
test/lib/reader_lifecycle_policy: get rid of lifecycle workarounds
test/lib/reader_lifecycle_policy: destroy_reader(): stop the semaphore
test/lib/reader_lifecycle_policy: use a more robust eviction mechanism
reader_concurrency_semaphore: wait for all permits to be destroyed in stop()
test/lib/reader_lifcecycle_policy: fix indentation
mutation_reader: reader_lifecycle_policy::destroy_reader(): require to be called on native shard
reader_lifecycle_policy implementations: fix indentation
mutation_reader: reader_lifecycle_policy::destroy_reader(): de-futurize reader parameter
mutation_reader: shard_reader::close(): wait on the remote reader
multishard_mutation_query: destroy remote parts in the foreground
mutation_reader: shard_reader::close(): close _reader
mutation_reader: reader_lifcecycle_policy::destroy_reader(): remove out-of-date comment
0948908502