1ed3f5c4af
Fixes a shutdown deadlock where a node hangs because `stale_versions_in_use()` blocks on stale `token_metadata` versions held by write handlers whose `MUTATION_DONE` responses can never arrive (transport is already stopped). Two manifestations depending on whether the shutting-down node is the topology coordinator: - Coordinator: do_drain → wait_for_group0_stop deadlocks because the topology coordinator fiber is stuck in barrier_and_drain → stale_versions_in_use(). - Non-coordinator: ss::stop → uninit_messaging_service deadlocks because the barrier_and_drain RPC handler holds the gate open. The non-coordinator case was fixed in PR #24714 (cancel all write requests on storage_proxy shutdown), but its test never actually failed — the write handler always captured the current token_metadata version because `pause_before_barrier_and_drain` used `one_shot=True,` so only the first `barrier_and_drain` was paused. The topology state hadn't advanced by that point, meaning the write handler's ERM version matched the current version and `stale_versions_in_use()` returned immediately. The coordinator case was not covered at all. Cancel all write response handlers on all shards right after `stop_transport()` in `do_drain()`. This releases their ERMs and the associated stale token_metadata versions, unblocking `stale_versions_in_use()`. Fixed the test to ensure the write handler holds a stale version: use one_shot=False, let the first barrier_and_drain through (version still current), then wait for the second one (version now stale). Extended to cover both coordinator and non-coordinator shutdown on the same 2-node cluster. Also includes supporting changes: - error_injection: release wait_for_message waiters on disable() so the test can atomically unblock paused handlers - error_injection: add non-shared mode to wait_for_message for per-invocation message semantics - scylla_cluster.py: allow stop() to bypass start_stop_lock so SIGKILL works while stop_gracefully is blocked Fixes: SCYLLADB-1842 Refs: scylladb/scylladb#23665 backports: SCYLLADB-1842 reported a failure in 2025.1, so we need to backport to all versions starting from 2025.1 Closes scylladb/scylladb#29882 * https://github.com/scylladb/scylladb: storage_service: cancel write handlers during drain to prevent shutdown deadlock test_unfinished_writes_during_shutdown: extend to cover coordinator shutdown test_unfinished_writes_during_shutdown: fix to reproduce the shutdown deadlock test_unfinished_writes_during_shutdown: await add_last_node_task instead of cancelling it test_unfinished_writes_during_shutdown: add timeout and deadlock detection for shutdown_task test: scylla_cluster: allow stop() to bypass start_stop_lock error_injection: add non-shared mode to wait_for_message error_injection: release waiters when injection is disabled
Scylla
What is Scylla?
Scylla is the real-time big data database that is API-compatible with Apache Cassandra and Amazon DynamoDB. Scylla embraces a shared-nothing approach that increases throughput and storage capacity to realize order-of-magnitude performance improvements and reduce hardware costs.
For more information, please see the ScyllaDB web site.
Build Prerequisites
Scylla is fairly fussy about its build environment, requiring very recent versions of the C++23 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers a frozen toolchain. This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).
Building Scylla
Building Scylla with the frozen toolchain dbuild is as easy as:
$ git submodule update --init --force --recursive
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
For further information, please see:
- Developer documentation for more information on building Scylla.
- Build documentation on how to build Scylla binaries, tests, and packages.
- Docker image build documentation for information on how to build Docker images.
Running Scylla
To start Scylla server, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --workdir tmp --smp 1 --developer-mode 1
This will start a Scylla node with one CPU core allocated to it and data files stored in the tmp directory.
The --developer-mode is needed to disable the various checks Scylla performs at startup to ensure the machine is configured for maximum performance (not relevant on development workstations).
Please note that you need to run Scylla with dbuild if you built it with the frozen toolchain.
For more run options, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --help
Testing
See test.py manual.
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its API - CQL. There is also support for the API of Amazon DynamoDB™, which needs to be enabled and configured in order to be used. For more information on how to enable the DynamoDB™ API in Scylla, and the current compatibility of this feature as well as Scylla-specific extensions, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found here. Seastar documentation can be found here. User documentation can be found here.
Training
Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.
Contributing to Scylla
If you want to report a bug or submit a pull request or a patch, please read the contribution guidelines.
If you are a developer working on Scylla, please read the developer guidelines.
Contact
- The community forum and Slack channel are for users to discuss configuration, management, and operations of ScyllaDB.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.