60af2f3cb2
Prototype implementation of format suggested/requested by @avikivity: Divides segments into disk-write-alignment sized pages, each tagged with segment ID + CRC of data content. When read, we both verify sector integrity (CRC) to detect corruption, as well as matching ID read with expected one. If the latter mismatches we have a prematurely terminated segment (read truncation), which, depending on whether the CL is written in batch or periodic mode, as well as explicit sync, can mean data loss. Note: all-zero pages are treated as kosher, both to align with newly allocated segments, as well as fully terminated (zero-page) ones. Note: This is a preview/RFC - the rest of the file format is not modified. At least parts of entry CRC could probably be removed, but I have not done so yet (needs some thinking). Note: Some slight abstraction breaks in impl. and probably less than maximal efficiency. v2: * Removed entry CRC:s in file format. * Added docs on format v3 * Added one more test for recycling-truncation v3: * Fixed typos in size calc and docs * Changed sect metadata order * Explicit iter type Closes scylladb/scylladb#15494 * github.com:scylladb/scylladb: commitlog_test: Add test for replaying large-ish mutation commitlog_test: Add additional test for segmnent truncation docs: Add docs on commitlog format 3 commitlog: Remove entry CRC from file format commitlog: Implement new format using CRC:ed sectors commitlog: Add iterator adaptor for doing buffer splitting into sub-page ranges fragmented_temporary_buffer: Add const iterator access to underlying buffers commitlog_replayer: differentiate between truncated file and corrupt entries
Scylla developer documentation
This folder contains developer-oriented documentation concerning the ScyllaDB codebase. We also have a wiki, which contains additional developer-oriented documentation. There is currently no clear definition of what goes where, so when looking for something be sure to check both.
Seastar documentation can be found here.
User documentation can be found on docs.scylladb.com
For information on how to build Scylla and how to contribute visit HACKING.md and CONTRIBUTING.md.