1d8234f52d
" The current printout is has multiple problems: * It is segregated by state, each having its own sorting criteria; * Number of permits and count resources is collapsed in to a single column, not clear which is the one printed. * Number of available/initial units of the semaphore are not printed; This series solves all this problems: * It merges all states into a single table, sorted by memory consumption, in descending order. * It separates number of permits and count resources into separate columns. * Prints a summary of the semaphore units. * Provides a cap on the maximum amount of printable lines, to not blow up the logs. The goal of all this is to make it easy to find the culprit a semaphore problem: easily spot the big memory consumers, then unpack the name column to determine which table and code path is responsible. This brings the printout close to the recently `scylla reads` scylla-gdb.py command, providing a uniform report format across the two tools. Example report: INFO 2021-05-07 09:52:16,806 [shard 0] testlog - With max-lines=4: Semaphore reader_concurrency_semaphore_dump_reader_diganostics with 8/2147483647 count and 263599186/9223372036854775807 memory resources: user request, dumping permit diagnostics: permits count memory table/description/state 7 2 77M ks.tbl1/op1/active 6 3 59M ks.tbl1/op0/active 4 0 36M ks.tbl1/op2/active 3 1 36M ks.tbl0/op2/active 11 2 43M permits omitted for brevity 31 8 251M total " * 'reader-concurrency-semaphore-dump-improvement/v1' of https://github.com/denesb/scylla: test: reader_concurrency_test: add reader_concurrency_semaphore_dump_reader_diganostics reader_concurrency_semaphore: dump_reader_diagnostics(): print more information in the header reader_concurrency_semaphore: dump_reader_diagnostics(): cap number of printed lines reader_concurrency_semaphore: dump_reader_diagnostics(): sort lines in descending order reader_concurrency_semaphore: dump_reader_diagnostics(): merge all states into a single table reader_concurrency_semaphore: dump_reader_diagnostics(): separate number of permits and count resources
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.