d0b3f3dfe8
The concept of seed and the different behaviour between seed nodes and non seed nodes generate a lot of confusion, complication and error for users. For example, how to add a seed node into into a cluster, how to promote a non seed node to a seed node, how to choose seeds node in multiple DC setup, edit config files for seeds, why seed node does not bootstrap. If we remove the concept of seed, it will get much easier for users. After this series, seed config option is only used once when a new node joins a cluster. Major changes: - Seed nodes are only used as the initial contact point nodes. - Seed nodes now perform bootstrap. The only exception is the first node in the cluster. - The unsafe auto_bootstrap option is now ignored. - Gossip shadow round now attempts to talk to all nodes instead of just seed nodes. Manual test: - bootstrap n1, n2, n3 (n1 and n2 are listed as seed, check only n1 will skip bootstrap, n2 and n3 will bootstrap) - shtudown n1, n2, n3 - start n2 (check non seed node can boot) - start n1 (check n1 talks to both n2 and n3) - start n3 (check n3 talks to both n1 and n3) Upgrade/Downgrade test: - Initialize cluster Start 3 node with n1, n2, n3 using old version n1 and n2 are listed as seed - Test upgrade starting from seed nodes Rolling restart n1 using new version Rolling restart n2 using new version Rolling restart n3 using new version - Test downgrade to old version Rolling restart n1 using old version Rolling restart n2 using old version Rolling restart n3 using old version - Test upgrade starting from non seed nodes Rolling restart n3 using new version Rolling restart n2 using new version Rolling restart n1 using new version Notes on upgrade procedure: There is no special procedure needed to upgrade to Scylla without seed concept. Rolling upgrade node one by one is good enough. Fixes: #6845 Tests: ./test.py + update_cluster_layout_tests.py + manual test
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.
- Packaging documentation on how to build Scylla packages for different Linux distributions.
- 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 in ./docs and on the wiki. 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 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.