77121247bd
During tablet migration with S3-backed storage, every streaming attempt fails with `std::logic_error("unsupported operation on s3 readable file")`. The tablet load balancer continuously retries, and after prolonged failure the cluster degrades — S3 objects start returning 404, write timeouts cascade, and the cluster becomes effectively non-functional.
Two bugs in `sstable_stream_sink_impl`:
1. **`output()` used `open_file()` + `make_file_output_stream()`** to create the writable stream for receiving SSTable data on the follower side. For object storage backends, `open_file()` ignores write flags and always returns a read-only `readable_file`. Writing through it throws `std::logic_error("unsupported operation on s3 readable file")`, breaking all tablet migration streaming with S3-backed storage.
2. **`load_metadata()` used `file_exists()` on a local filesystem path** to check whether the Scylla metadata component exists before loading it. For S3-backed storage this always returns false. When encryption is enabled, each streamed SSTable component gets a fresh encryption key (because the previous key from scylla metadata is never loaded from S3). Only the last key survives, making all other components unreadable — decryption with the wrong key produces garbage, leading to parse failures or OOM crashes on `sst->load()`.
- Replace `open_file()` + `make_file_output_stream()` with `make_component_sink()` + `output_stream()`, which correctly produces an upload sink for S3/GCS and a `file_data_sink` for local filesystem. This is the same mechanism already used by `save_metadata()` in the same class.
- Replace `file_exists(local_path)` with `_sst->_storage->exists()` which correctly checks for the component on whatever backend the SSTable uses.
- C++ unit tests (`test_stream_sink_write_local`, `test_stream_sink_write_s3`, `test_stream_sink_write_gs`) in `file_stream_test.cc` exercise `sstable_stream_sink_impl::output()` with all storage backends.
- Parametrize the existing `test_file_streaming_respects_encryption` Python integration test over local, S3, and GCS backends using a new `storage` fixture in `test/cluster/conftest.py`. The S3/GCS variants exercise the `load_metadata` fix — without it, streaming fails with `malformed_sstable_exception` (decryption with the wrong key) and the migration never completes.
- Add reusable `make_cfg()` and `make_ks_opts()` helpers to `test/cluster/util.py` for building storage-parametrized server config and keyspace CQL options.
Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-1704
Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-1829
Backport is not needed since no release supports object-storage-backed keyspaces.
Closes scylladb/scylladb#29698
* github.com:scylladb/scylladb:
test: parametrize encrypted streaming test with storage backends
sstables: fix load_metadata to check S3 for scylla metadata component
test: verify sstable stream sink writes to object storage
sstables: use make_component_sink for stream sink output
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.