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The limit is enforced by controlling average per-shard tablet replica count in a given DC, which is controlled by per-table tablet count. This is effective in respecting the limit on individual shards as long as tablet replicas are distributed evenly between shards. There is no attempt to move tablets around in order to enforce limits on individual shards in case of imbalance between shards. If the average per-shard tablet count exceeds the limit, all tables which contribute to it (have replicas in the DC) are scaled down by the same factor. Due to rounding up to the nearest power of 2, we may overshoot the per-shard goal by at most a factor of 2. If different DCs want different scale factors of a given table, the lowest scale factor is chosen for a given table. The limit is configurable. It's a global per-cluster config which controls how many tablet replicas per shard in total we consider to be still ok. It controls tablet allocator behavior, when choosing initial tablet count. Even though it's a per-node config, we don't support different limits per node. All nodes must have the same value of that config. It's similar in that regard to other scheduler config items like tablets_initial_scale_factor and target_tablet_size_in_bytes.
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.