Adds an opt-in O_DIRECT write path for background SSTable producers,
bypassing the OS page cache for data that is unlikely to be re-read
soon after being written. Memtable flushes remain buffered.
Enabled via two new YAML knobs:
- background_write_disk_access_mode: standard (default) | direct
- direct_write_buffer_size: 1MiB (default; aligned up to FS block
size, auto-grown to fit a worst-case compressed chunk)
The path is gated by config, table compression being enabled, and an
OperationType allowlist in DataComponent. The allowlist is exhaustive
over OperationType: any new value left unclassified fails static
initialization.
Operations on the DIO path: COMPACTION, MAJOR_COMPACTION,
TOMBSTONE_COMPACTION, ANTICOMPACTION, GARBAGE_COLLECT, CLEANUP,
UPGRADE_SSTABLES, WRITE, STREAM (chunked receiver only), RELOCATE,
UNKNOWN (offline sstablesplit).
Operations off the DIO path:
- FLUSH (policy: just-flushed data is hot, keep in page cache)
- SCRUB (correctness: tryAppend needs mark/resetAndTruncate)
- Zero-Copy Streaming (bypasses DataComponent.buildWriter)
- Uncompressed writers (only CompressedSequentialWriter has a DIO
subclass in this change)
StartupChecks fails fast if 'direct' is requested on a platform/FS
that does not support O_DIRECT.
patch by Sam Lightfoot; reviewed by Ariel Weisberg, Dmitry Konstantinov for CASSANDRA-21134
Both CASSANDRA-18120 and CASSANDRA-19946 updated cassandra_latest.yaml but not the corresponding test configs
patch by Mick Semb Wever; reviewed by Brandon Williams, Tiago L. Alves for CASSANDRA-20002
This patch adds a new configuration file, cassandra_latest.yaml, which changes
some of the settings to use new features we usually recommend to users,
including:
- Big Trie-Indexed SSTables
- Trie memtables
- Unified Compaction Strategy
- Storage Attached Index
- Off-heap objects memtables
- Direct-write commit log
- No storage compatibility
These changes are applied in new test targets for unit, in-jvm and python dtests that are
run pre-commit. When changes are made to the new config file, python dtest will use it
directly, but unit and in-jvm dtests require updates, respectively, to latest_diff.yaml
and InstanceConfig.java.
patch by Branimir Lambov; reviewed by Berenguer Blasi for CASSANDRA-18753
samlightfoot