4018dc7f0d
File based stream is a new feature that optimizes tablet movement
significantly. It streams the entire SSTable files without deserializing
SSTable files into mutation fragments and re-serializing them back into
SSTables on receiving nodes. As a result, less data is streamed over the
network, and less CPU is consumed, especially for data models that
contain small cells.
The following patches are imported from the scylla enterprise:
*) Merge 'Introduce file stream for tablet' from Asias He
This patch uses Seastar RPC stream interface to stream sstable files on
network for tablet migration.
It streams sstables instead of mutation fragments. The file based
stream has multiple advantages over the mutation streaming.
- No serialization or deserialization for mutation fragments
- No need to read and process each mutation fragments
- On wire data is more compact and smaller
In the test below, a significant speed up is observed.
Two nodes, 1 shard per node, 1 initial_tablets:
- Start node 1
- Insert 10M rows of data with c-s
- Bootstrap node 2
Node 1 will migration data to node2 with the file stream.
Test results:
1) File stream: bytes on wire = 1132006250 bytes, bw = 836MB/s
[shard 0:stre] stream_blob - stream_sstables[eadaa8e0-a4f2-4cc6-bf10-39ad1ce106b0]
Finished sending sstable_nr=2 files_nr=18 files={} range=(-1,9223372036854775807] bytes_sent=1132006250 stream_bw=836MB/s
[shard 0:stre] storage_service - Streaming for tablet migration of a4f68900-568a-11ee-b7b9-c2b13945eed2:1 took 1.08004s seconds
2) Mutation stream: bytes on wire = 3030004736 bytes, bw = 125410.87 KiB/s = 128MB/s
[shard 0:stre] stream_session - [Stream #406dc8b0-56b5-11ee-bc2d-000bf4871058]
Streaming plan for Tablet migration-ks1-index-0 succeeded, peers={127.0.0.1}, tx=0 KiB, 0.00 KiB/s, rx=2958989 KiB, 125410.87 KiB/s
[shard 0:stre] storage_service - Streaming for tablet migration of a4f68900-568a-11ee-b7b9-c2b13945eed2:1 took 23.5992s seconds
Test Summary:
File stream v.s. Mutation stream improvements
- Stream bandwidth = 836 / 128 (MB/s) = 6.53X
- Stream time = 23.60 / 1.08 (Seconds) = 21.85X
- Stream bytes on wire = 3030004736 / 1132006250 (Bytes)= 2.67X
Closes scylladb/scylla-enterprise#3438
* github.com:scylladb/scylla-enterprise:
tests: Add file_stream_test
streaming: Implement file stream for tablet
*) streaming: Use new take_storage_snapshot interface
The new take_storage_snapshot returns a file object instead of a file
name. This allows the file stream sender to read from the file even if
the file is deleted by compaction.
Closes scylladb/scylla-enterprise#3728
*) streaming: Protect unsupported file types for file stream
Currently, we assume the file streamed over the stream_blob rpc verb is
a sstable file. This patch rejects the unsupported file types on the
receiver side. This allows us to stream more file types later using the
current file stream infrastructure without worrying about old nodes
processing the new file types in the wrong way.
- The file_ops::noop is renamed to file_ops::stream_sstables to be
explicit about the file types
- A missing test_file_stream_error_injection is added to the idl
Fixes: #3846
Tests: test_unsupported_file_ops
Closes scylladb/scylla-enterprise#3847
*) idl: Add service::session_id id to idl
It will be used in the next patch.
Refs #3907
*) streaming: Protect file stream with topology_guard
Similar to "storage_service, tablets: Use session to guard tablet
streaming", this patch protects file stream with topology_guard.
Fixes #3907
*) streaming: Take service topology_guard under the try block
Taking the service::topology_guard could throw. Currently, it throws
outside the try block, so the rpc sink will not be closed, causing the
following assertion:
```
scylla: seastar/include/seastar/rpc/rpc_impl.hh:815: virtual
seastar::rpc::sink_impl<netw::serializer,
streaming::stream_blob_cmd_data>::~sink_impl() [Serializer =
netw::serializer, Out = <streaming::stream_blob_cmd_data>]: Assertion
`this->_con->get()->sink_closed()' failed.
```
To fix, move more code including the topology_guard taking code to the
try block.
Fixes https://github.com/scylladb/scylla-enterprise/issues/4106
Closes scylladb/scylla-enterprise#4110
*) Merge 'Preserve original SSTable state with file based tablet migration' from Raphael "Raph" Carvalho
We're not preserving the SSTable state across file based migration, so
staging SSTables for example are being placed into main directory, and
consequently, we're mixing staging and non-staging data, losing the
ability to continue from where the old replica left off.
It's expected that the view update backlog is transferred from old
into new replica, as migration doesn't wait for leaving replica to
complete view update work (which can take long). Elasticity is preferred.
So this fix guarantees that the state of the SSTable will be preserved
by propagating it in form of subdirectory (each subdirectory is
statically mapped with a particular state).
The staging sstables aren't being registered into view update generator
yet, as that's supposed to be fixed in OSS (more details can be found
at https://github.com/scylladb/scylladb/issues/19149).
Fixes #4265.
Closes scylladb/scylla-enterprise#4267
* github.com:scylladb/scylla-enterprise:
tablet: Preserve original SSTable state with file based tablet migration
sstables: Add get method for sstable state
*) sstable: (Re-)add shareabled_components getter
*) Merge 'File streaming sstables: Use sstable source/sink to transfer snapshots' from Calle Wilund
Fixes #4246
Alternative approach/better separation of concern, transport vs. sstable layer. Builds on #4472, but fancier.
Ensures we transfer and pre-process scylla metadata for streamed
file blobs first, then properly apply receiving nodes local config
by using a source and sink layer exported from sstables, which
handles things like ordering, metadata filtering (on source) as well
as handling metadata and proper IO paths when writing data on
receiver node (sink).
This implementation maintains the statelessness of the current
design, and the delegated sink side will re-read and re-write the
metadata for each component processed. This is a little wasteful,
but the meta is small, and it is less error prone than trying to do
caching cross-shards etc. The transport is isolated from the
knowledge.
This is an alternative/complement to #4436 and #4472, fixing the
underlying issue. Note that while the layers/API:s here allows easy
fixing of other fundamental problems in the feature (such as
destination location etc), these are not included in the PR, to keep
it as close to the current behaviour as possible.
Closes scylladb/scylla-enterprise#4646
* github.com:scylladb/scylla-enterprise:
raft_tests: Copy/add a topology test with encryption
file streaming: Use sstable source/sink to transfer snapshots
sstables: Add source and sink objects + producers for transfering a snapshot
sstable::types: Add remove accessor for extension info in metadata
*) The change for error injection in merge commit 966ea5955dd8760:
File streaming now has "stream_mutation_fragments" error injection points
so test_table_dropped_during_streaming works with file streaming.
*) doc: document file-based streaming
This commit adds a description of the file-based streaming feature to the documentation.
It will be displayed in the docs using the scylladb_include_flag directive after
https://github.com/scylladb/scylladb/pull/20182 is merged, backported to branch-6.0,
and, in turn, branch-2024.2.
Refs https://github.com/scylladb/scylla-enterprise/issues/4585
Refs https://github.com/scylladb/scylla-enterprise/issues/4254
Closes scylladb/scylla-enterprise#4587
*) doc: move File-based streaming to the Tablets source file-based-streaming
This commit moves the description of file-based streaming from a common include file
to the regular doc source file where tablets are described.
Closes scylladb/scylla-enterprise#4652
*) streaming: sstable_stream_sink_impl: abort: prevent null pointer dereference
Closes scylladb/scylladb#22467
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 the ScyllaDB open source.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.