986491447b
View building from staging creates a reader from scratch (memtable
+ sstables - staging) for every partition, in order to calculate
the diff between new staging data and data in base sstable set,
and then pushes the result into the view replicas.
perf shows that the reader creation is very expensive:
+ 12.15% 10.75% reactor-3 scylla [.] lexicographical_tri_compare<compound_type<(allow_prefixes)0>::iterator, compound_type<(allow_prefixes)0>::iterator, legacy_compound_view<compound_type<(allow_prefixes)0> >::tri_comparator::operator()(managed_bytes_basic_view<(mutable_view)0>, managed_bytes
+ 10.01% 9.99% reactor-3 scylla [.] boost::icl::is_empty<boost::icl::continuous_interval<compatible_ring_position_or_view, std::less> >
+ 8.95% 8.94% reactor-3 scylla [.] legacy_compound_view<compound_type<(allow_prefixes)0> >::tri_comparator::operator()
+ 7.29% 7.28% reactor-3 scylla [.] dht::ring_position_tri_compare
+ 6.28% 6.27% reactor-3 scylla [.] dht::tri_compare
+ 4.11% 3.52% reactor-3 scylla [.] boost::icl::interval_base_map<boost::icl::interval_map<compatible_ring_position_or_view, std::unordered_set<seastar::lw_shared_ptr<sstables::sstable>, std::hash<seastar::lw_shared_ptr<sstables::sstable> >, std::equal_to<seastar::lw_shared_ptr<sstables::sst+ 4.09% 4.07% reactor-3 scylla [.] sstables::index_consume_entry_context<sstables::index_consumer>::process_state
+ 3.46% 0.93% reactor-3 scylla [.] sstables::sstable_run::will_introduce_overlapping
+ 2.53% 2.53% reactor-3 libstdc++.so.6 [.] std::_Rb_tree_increment
+ 2.45% 2.45% reactor-3 scylla [.] boost::icl::non_empty::exclusive_less<boost::icl::continuous_interval<compatible_ring_position_or_view, std::less> >
+ 2.14% 2.13% reactor-3 scylla [.] boost::icl::exclusive_less<boost::icl::continuous_interval<compatible_ring_position_or_view, std::less> >
+ 2.07% 2.07% reactor-3 scylla [.] logalloc::region_impl::free
+ 2.06% 1.91% reactor-3 scylla [.] sstables::index_consumer::consume_entry(sstables::parsed_partition_index_entry&&)::{lambda()#1}::operator()() const::{lambda()#1}::operator()
+ 2.04% 2.04% reactor-3 scylla [.] boost::icl::interval_base_map<boost::icl::interval_map<compatible_ring_position_or_view, std::unordered_set<seastar::lw_shared_ptr<sstables::sstable>, std::hash<seastar::lw_shared_ptr<sstables::sstable> >, std::equal_to<seastar::lw_shared_ptr<sstables::sst+ 1.87% 0.00% reactor-3 [kernel.kallsyms] [k] entry_SYSCALL_64_after_hwframe
+ 1.86% 0.00% reactor-3 [kernel.kallsyms] [k] do_syscall_64
+ 1.39% 1.38% reactor-3 libc.so.6 [.] __memcmp_avx2_movbe
+ 1.37% 0.92% reactor-3 scylla [.] boost::icl::segmental::join_left<boost::icl::interval_map<compatible_ring_position_or_view, std::unordered_set<seastar::lw_shared_ptr<sstables::sstable>, std::hash<seastar::lw_shared_ptr<sstables::sstable> >, std::equal_to<seastar::lw_shared_ptr<sstables::
+ 1.34% 1.33% reactor-3 scylla [.] logalloc::region_impl::alloc_small
+ 1.33% 1.33% reactor-3 scylla [.] seastar::memory::small_pool::add_more_objects
+ 1.30% 0.35% reactor-3 scylla [.] seastar::reactor::do_run
+ 1.29% 1.29% reactor-3 scylla [.] seastar::memory::allocate
+ 1.19% 0.05% reactor-3 libc.so.6 [.] syscall
+ 1.16% 1.04% reactor-3 scylla [.] boost::icl::interval_base_map<boost::icl::interval_map<compatible_ring_position_or_view, std::unordered_set<seastar::lw_shared_ptr<sstables::sstable>, std::hash<seastar::lw_shared_ptr<sstables::sstable> >, std::equal_to<seastar::lw_shared_ptr<sstables::sst
+ 1.07% 0.79% reactor-3 scylla [.] sstables::partitioned_sstable_set::insert
That shows some significant amount of work for inserting sstables
into the interval map and maintaining the sstable run (which sorts
fragments by first key and checks for overlapping).
The interval map is known for having issues with L0 sstables, as
it will have to be replicated almost to every single interval
stored by the map, causing terrible space and time complexity.
With enough L0 sstables, it can fall into quadratic behavior.
This overhead is fixed by not building a new fresh sstable set
when recreating the reader, but rather supplying a predicate
to sstable set that will filter out staging sstables when
creating either a single-key or range scan reader.
This could have another benefit over today's approach which
may incorrectly consider a staging sstable as non-staging, if
the staging sst wasn't included in the current batch for view
building.
With this improvement, view building was measured to be 3x faster.
from
INFO 2023-06-16 12:36:40,014 [shard 0] view_update_generator - Processed keyspace1.standard1: 5 sstables in 963957ms = 50kB/s
to
INFO 2023-06-16 14:47:12,129 [shard 0] view_update_generator - Processed keyspace1.standard1: 5 sstables in 319899ms = 150kB/s
Refs #14089.
Fixes #14244.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
(cherry picked from commit 1d8cb32a5d)
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closes #14764
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++20 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 APIs - CQL and Thrift. 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 users mailing list 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.