c3da9f2bd4
Alternator supports four ways in which write operations can use quorum writes or LWT or both, which we called "write isolation policies". Until this patch, Alternator defaulted to the most generally safe policy, "always_use_lwt". This default could have been overriden for each table separately, but there was no way to change this default for all tables. This patch adds a "--alternator-write-isolation" configuration option which allows changing the default. Moreover, @dorlaor asked that users must *explicitly* choose this default mode, and not get "always_use_lwt" without noticing. The previous default, "always_use_lwt" supports any workload correctly but because it uses LWT for all writes it may be disappointingly slow for users who run write-only workloads (including most benchmarks) - such users might find the slow writes so disappointing that they will drop Scylla. Conversely, a default of "forbid_rmw" will be faster and still correct, but will fail on workloads which need read-modify-write operations - and suprise users that need these operations. So Dor asked that that *none* of the write modes be made the default, and users must make an informed choice between the different write modes, rather than being disappointed by a default choice they weren't aware of. So after this patch, Scylla refuses to boot if Alternator is enabled but a "--alternator-write-isolation" option is missing. The patch also modifies the relevant documentation, adds the same option to our docker image, and the modifies the test-running script test/alternator/run to run Scylla with the old default mode (always_use_lwt), which we need because we want to test RMW operations as well. Fixes #6452 Signed-off-by: Nadav Har'El <nyh@scylladb.com> Message-Id: <20200524160338.108417-1-nyh@scylladb.com>
Scylla
Quick-start
To get the build going quickly, Scylla offers a frozen toolchain which would build and run Scylla using a pre-configured Docker image. Using the frozen toolchain will also isolate all of the installed dependencies in a Docker container. Assuming you have met the toolchain prerequisites, which is running Docker in user mode, building and running is as easy as:
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
$ ./tools/toolchain/dbuild ./build/release/scylla --developer-mode 1
Please see HACKING.md for detailed information on building and developing Scylla.
Note: GCC >= 8.1.1 is required to compile Scylla.
Running Scylla
- Run Scylla
./build/release/scylla
- run Scylla with one CPU and ./tmp as work directory
./build/release/scylla --workdir tmp --smp 1
- For more run options:
./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 experimental support for the API of Amazon DynamoDB, but being experimental it needs to be explicitly enabled to be used. For more information on how to enable the experimental DynamoDB compatibility in Scylla, and the current limitations of this feature, 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.
Building a CentOS-based Docker image
Build a Docker image with:
cd dist/docker/redhat
docker build -t <image-name> .
This build is based on executables downloaded from downloads.scylladb.com, not on the executables built in this source directory. See further instructions in dist/docker/redhat/README.md to build a docker image from your own executables.
Run the image with:
docker run -p $(hostname -i):9042:9042 -i -t <image name>