fedd838b9d
There are two semaphores in table for synchronizing changes to sstable list: sstable_set_mutation_sem: used to serialize two concurrent operations updating the list, to prevent them from racing with each other. sstable_deletion_sem: A deletion guard, used to serialize deletion and iteration over the list, to prevent iteration from finding deleted files on disk. they're always taken in this order to avoid deadlocks: sstable_set_mutation_sem -> sstable_deletion_sem. problem: A = tablet cleanup B = take_snapshot() 1) A acquires sstable_set_mutation_sem for updating list 2) A acquires sstable_deletion_sem, then delete sstable before updating list 3) A releases sstable_deletion_sem, then yield 4) B acquires sstable_deletion_sem 5) B iterates through list and bumps sstable deleted in step 2 6) B fails since it cannot find the file on disk Initial reaction is to say that no procedure must delete sstable before updating the list, that's true. But we want a iteration, running concurrently to cleanup, to not find sstables being removed from the system. Otherwise, e.g. snapshot works with sstables of a tablet that was just cleaned up. That's achieved by serializing iteration with list update. Since sstable_deletion_sem is used within the scope of deletion only, it's useless for achieving this. Cleanup could acquire the deletion sem when preparing list updates, and then pass the "permit" to deletion function, but then sstable_deletion_sem would essentially become sstable_set_mutation_sem, which was created exactly to protect the list update. That being said, it makes sense to merge both semaphores. Also things become easier to reason about, and we don't have to worry about deadlocks anymore. The deletion goes through sstable_list_builder, which holds a permit throughout its lifetime, which guarantees that list updates and deletion are atomic to other concurrent operations. The interface becomes less error prone with that. It allowed us to find discard_sstables() was doing deletion without any permit, meaning another race could happen between truncate and snapshot. So we're fixing race of (truncate|cleanup) with take_snapshot, as far as we know. It's possible another unknown races are fixed as well. Fixes #23049. Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com> Closes scylladb/scylladb#23117
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cqlpy - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.