a50e6215aa
Add three cluster tests that verify no data resurrection occurs when
tombstone GC runs on the repaired sstable set under incremental repair
with tombstone_gc=repair mode.
All tests use propagation_delay_in_seconds=0 so that tombstones become
GC-eligible immediately after repair_time is committed (gc_before =
repair_time), allowing the scenarios to exercise the actual GC eligibility
path without artificial sleeps.
(test_tombstone_gc_no_resurrection_basic_ordering)
Data D (ts=1) and tombstone T (ts=2) are written to all replicas and
flushed before repair. Repair captures both in the repairing snapshot
and promotes them to repaired. Once repair_time is committed, T is
GC-eligible (T.deletion_time < gc_before = repair_time).
The test verifies that compaction on the repaired set does NOT purge T,
because D is already in repaired (mark_sstable_as_repaired() completes
on all replicas before repair_time is committed to Raft) and clamps
max_purgeable to D.timestamp=1 < T.timestamp=2.
(test_tombstone_gc_no_resurrection_hints_flush_failure)
The repair_flush_hints_batchlog_handler_bm_uninitialized injection causes
hints flush to fail on one node. When hints flush fails, flush_time stays
at gc_clock::time_point{} (epoch). This propagates as repair_time=epoch
committed to system.tablets, so gc_before = epoch - propagation_delay is
effectively the minimum possible time. No tombstone has a deletion_time
older than epoch, so T is never GC-eligible from this repair.
The test verifies that repair_time does not advance to a meaningful value
after a failed hints flush, and that compaction on the repaired set does
not purge T (key remains deleted, no resurrection).
(test_tombstone_gc_no_resurrection_propagation_delay)
Simulates a write D carrying an old CQL USING TIMESTAMP (ts_d = now-2h)
that was stored as a hint while a replica was down, and a tombstone T
with a higher timestamp (ts_t = now-90min, ts_t > ts_d) that was written
to all live replicas. After the replica restarts, repair flushes hints
synchronously before taking the repairing snapshot, guaranteeing D is
delivered and captured in repairing before the snapshot.
After mark_sstable_as_repaired() promotes D to repaired, the coordinator
commits repair_time. gc_before = repair_time > T.deletion_time so T is
GC-eligible. The test verifies that compaction on the repaired set does
NOT purge T: D (ts_d < ts_t) is already in repaired, clamping
max_purgeable = ts_d < ts_t = T.timestamp, so T is not purgeable.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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.