8dfd455001
- Fix table drop blocking for the full client timeout when in-flight writes can't reach quorum
- Handle unhandled timeout exception in the wait-for-leader loop during group startup
When a strongly consistent table is dropped, `schedule_raft_group_deletion`() calls `g->close()` which waits for all in-flight operations to release their gate holders. But other nodes may have already destroyed their raft servers for this group, so an in-flight write on the leader cannot reach quorum and hangs until the client timeout expires (~seconds), unnecessarily delaying group deletion.
Additionally, the wait-for-leader loop in groups_manager::update() uses abort_on_expiry with a 60-second timeout but never catches the exception if it fires, leaving the group in an indeterminate state.
SCYLLADB-2080 fix:
- Reorder `schedule_raft_group_deletion`: initiate gate close (prevents new operations), then abort the raft server (unblocks stuck writes by causing `raft::stopped_error`), then await the gate future (resolves immediately since holders are released).
- Handle `raft::stopped_error` in the coordinator's top-level catch blocks (both write and read paths): if the table no longer exists, return `no_such_column_family` (CQL layer converts to InvalidRequest: unconfigured table). Otherwise fall through to the default timeout handling.
- Replace gate->hold() with try_hold() + on_internal_error in acquire_server, with a comment explaining why the gate can never be closed at that point (table removal in `schema_applier::commit_on_shard` precedes gate closure, with no scheduling point in between).
Timeout handling fix:
- Use `coroutine::as_future` in the wait-for-leader loop to catch timeout exceptions gracefully — log a warning and break out instead of propagating unhandled.
Includes a cluster test reproducer (test_drop_table_unblocks_stuck_write) that:
1. Pauses a write on the leader before add_entry
2. Drops the table (follower destroys its group immediately)
3. Resumes the write — verifies it fails promptly with InvalidRequest ("unconfigured table") instead of hanging for 15 seconds
backport: no need, strong consistency is not released yet
Fixes: SCYLLADB-2080
Closes scylladb/scylladb#30105
* github.com:scylladb/scylladb:
strong consistency/groups_manager: handle timeout in update() wait-for-leader loop
strong consistency: abort raft server before gate close when dropping a table
test/cluster: rewrite test_queries_while_dropping_table for SCYLLADB-2080
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.