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This will result in new tables having at least 10 tablet replicas per shard by default. We want this to reduce tablet load imbalance due to differences in tablet count per shard, where some shards have 1 tablet and some shards have 2 tablets. With higher tablet count per shard, this difference-by-one is less relevant. Fixes #21967 In some tests, we explicity set the initial scale to 1 as some of the existing tests assume 1 compaction group per shard. test.py uses a lower default. Having many tablets per shard slows down certain topology operations like decommission/replace/removenode, where the running time is proportional to tablet count, not data size, because constant cost (latency) of migration dominates. This latency is due to group0 operations and barriers. This is especially pronounced in debug mode. Scheduler allows at most 2 migrations per shard, so this latency becomes a determining factor for decommission speed. To avoid this problem in tests, we use lower default for tablet count per shard, 2 in debug/dev mode and 4 in release mode. Alternatively, we could compensate by allowing more concurrency when migrating small tablets, but there's no infrastructure for that yet. I observed that with 10 tablets per shard, debug-mode topology_custom.mv/test_mv_topology_change starts to time-out during removenode (30 s).
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.