a2b2a42936
When a node shuts down, do_drain() calls stop_transport() which tears
down the messaging service. After this point, MUTATION_DONE responses
from replicas can no longer reach the coordinator, so any in-flight
write_response_handlers will never complete naturally. These handlers
hold ERMs referencing stale token_metadata versions.
If the topology coordinator calls barrier_and_drain (either on itself
or via RPC), it blocks in stale_versions_in_use() waiting for these
stale versions to be released. This causes:
- On the coordinator node: do_drain -> wait_for_group0_stop deadlock
(the topology coordinator fiber is stuck in barrier_and_drain).
- On non-coordinator nodes: ss::stop -> uninit_messaging_service
deadlock (the barrier_and_drain RPC handler holds the gate open).
Fix: 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().
Heap-allocate _write_handlers_gate and add an allow_new parameter to
cancel_all_write_response_handlers(). When allow_new=true (used by
do_drain), the gate is closed and swapped with a fresh one — existing
handlers are waited on while new handlers can still be created. This
avoids blocking internal writes (paxos learn, compaction history
updates) that still need to create handlers during the remainder of
the drain sequence. When allow_new=false (used by drain_on_shutdown),
the gate is closed permanently — no new handlers can be created after
final shutdown.
Update test_lwt_shutdown to wait for 'Stop transport: done' instead
of 'Shutting down storage proxy RPC verbs'. The latter message is
now only logged after do_drain() completes, but do_drain() blocks
in cancel_all_write_response_handlers() waiting for the background
paxos learn handler — which is exactly what the test needs to release
before shutdown can proceed.
Fixes: SCYLLADB-2163
Refs: scylladb/scylladb#23665
(cherry picked from commit 2927f0dd21)
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.