4d9271df98
This is yet another part in the BTI index project. Overarching issue: https://github.com/scylladb/scylladb/issues/19191 Previous part: https://github.com/scylladb/scylladb/pull/25626 Next parts: make `ms` the default. Then, general tweaks and improvements. Later, potentially a full `da` format implementation. This patch series introduces a new, Scylla-only sstable format version `ms`, which is like `me`, but with the index components (Summary.db and Index.db) replaced with BTI index components (Partitions.db and Rows.db), as they are in Cassandra 5.0's `da` format version. (Eventually we want to just implement `da`, but there are several other changes (unrelated to the index files) between `me` and `da`. By adding this `ms` as an intermediate step we can adapt the new index formats without dragging all the other changes into the mix (and raising the risk of regressions, which is already high)). The high-level structure of the PR is: 1. Introduce new component types — `Partitions` and `Rows`. 2. Teach `class sstable` to open them when they exist. 3. Teach the sstable writer how to write index data to them. 4. Teach `class sstable` and unit tests how to deal with sstables that have no `Index` or `Summary` (but have `Partitions` and `Rows` instead). 5. Introduce the new sstable version `ms`, specify that it has `Partitions` and `Rows` instead of `Index` and `Summary`. 6. Prepare unit tests for the appearance of `ms`. 7. Enable `ms` in unit tests. 8. Make `ms` enablable via db::config (with a silent fall back to `me` until the new `MS_SSTABLE_FORMAT` cluster feature is enabled). 9. Prepare integration tests for the appearance of `ms`. 10. Enable both `ms` and `me` in tests where we want both versions to be tested. This series doesn't make `ms` the default yet, because that requires teaching Scylla Manager and a few dtests about the new format first. It can be enabled by setting `sstable_format: ms` in the config. Per a review request, here is an example from `perf_fast_forward`, demonstrating some motivation for a new format. (Although not the main one. The main motivations are getting rid of restrictions on the RAM:disk ratio, and index read throughput for datasets with tiny partitions). The dataset was populated with `build/release/scylla perf-fast-forward --smp=1 --sstable-format=$VERSION --data-directory=data.$VERSION --column-index-size-in-kb=1 --populate --random-seed=0`. This test involves a partition with 1000000 clustering rows (with 32-bit keys and 100-byte values) and ~500 index blocks, and queries a few particular rows from the partition. Since the branching factor for the BIG promoted index is 2 (it's a binary search), the lookup involves ~11.2 sequential page reads per row. The BTI format has a more reasonable branching factor, so it involves ~2.3 page reads per row. `build/release/scylla perf-fast-forward --smp=1 --data-directory=perf_fast_forward_data/me --run-tests=large-partition-select-few-rows`: ``` offset stride rows iterations avg aio aio (KiB) 500000 1 1 70 18.0 18 128 500001 1 1 647 19.0 19 132 0 1000000 1 748 15.0 15 116 0 500000 2 372 29.0 29 284 0 250000 4 227 56.0 56 504 0 125000 8 116 106.0 106 928 0 62500 16 67 195.0 195 1732 ``` `build/release/scylla perf-fast-forward --smp=1 --data-directory=perf_fast_forward_data/ms --run-tests=large-partition-select-few-rows`: ``` offset stride rows iterations avg aio aio (KiB) 500000 1 1 51 5.1 5 20 500001 1 1 64 5.3 5 20 0 1000000 1 679 4.0 4 16 0 500000 2 492 8.0 8 88 0 250000 4 804 16.0 16 232 0 125000 8 409 31.0 31 516 0 62500 16 97 54.0 54 1056 ``` Index file size comparison for the default `perf_fast_forward` tables with `--random-seed=0`: Large partition table (dominated by intra-partition index): 2.4 MB with `me`, 732 kB with `ms`. For the small partitions table (dominated by inter-partition index): 11 MB with `me`, 8.4 MB with `ms`. External tests: I ran SCT test `longevity-mv-si-4days-streaming-test` test on 6 nodes with 30 shards each for 8 hours. No anomalies were observed. New functionality, no backport needed. Closes scylladb/scylladb#26215 * github.com:scylladb/scylladb: test/boost/bloom_filter_test: add test_rebuild_from_temporary_hashes test/cluster: add test_bti_index.py test: prepare bypass_cache_test.py for `ms` sstables sstables/trie/bti_index_reader: add a failure injection in advance_lower_and_check_if_present test/cqlpy/test_sstable_validation.py: prepare the test for `ms` sstables tools/scylla-sstable: add `--sstable-version=?` to `scylla sstable write` db/config: expose "ms" format to the users via database config test: in Python tests, prepare some sstable filename regexes for `ms` sstables: add `ms` to `all_sstable_versions` test/boost/sstable_3_x_test: add `ms` sstables to multi-version tests test/lib/index_reader_assertions: skip some row index checks for BTI indexes test/boost/sstable_inexact_index_test: explicitly use a `me` sstable test/boost/sstable_datafile_test: skip test_broken_promoted_index_is_skipped for `ms` sstables test/resource: add `ms` sample sstable files for relevant tests test/boost/sstable_compaction_test: prepare for `ms` sstables. test/boost/index_reader_test: prepare for `ms` sstables test/boost/bloom_filter_tests: prepare for `ms` sstables test/boost/sstable_datafile_test: prepare for `ms` sstables test/boost/sstable_test: prepare for `ms` sstables. sstables: introduce `ms` sstable format version tools/scylla-sstable: default to "preferred" sstable version, not "highest" sstables/mx/reader: use the same hashed_key for the bloom filter and the index reader sstables/trie/bti_index_reader: allow the caller to passing a precalculated murmur hash sstables/trie/bti_partition_index_writer: in add(), get the key hash from the caller sstables/mx: make Index and Summary components optional sstables: open Partitions.db early when it's needed to populate key range for sharding metadata sstables: adapt sstable::set_first_and_last_keys to sstables without Summary sstables: implement an alternative way to rebuild bloom filters for sstables without Index utils/bloom_filter: add `add(const hashed_key&)` sstables: adapt estimated_keys_for_range to sstables without Summary sstables: make `sstable::estimated_keys_for_range` asynchronous sstables/sstable: compute get_estimated_key_count() from Statistics instead of Summary replica/database: add table::estimated_partitions_in_range() sstables/mx: implement sstable::has_partition_key using a regular read sstables: use BTI index for queries, when present and enabled sstables/mx/writer: populate BTI index files sstables: create and open BTI index files, when enabled sstables: introduce Partition and Rows component types sstables/mx/writer: make `_pi_write_m.partition_tombstone` a `sstables::deletion_time`
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.