scylladb/scylla

What is ScyllaDB ?

ScyllaDB is a high-performance NoSQL database optimized for speed and scalability. It is designed to efficiently handle large volumes of data with minimal latency, making it ideal for data-intensive applications.

ScyllaDB is distributed under the https://github.com/scylladb/scylladb/blob/master/LICENSE-ScyllaDB-Source-Available.md.

http://www.scylladb.com/

Quick start

To startup a Scylla single-node cluster in developer mode execute:

console
$ docker run --name some-scylla --hostname some-scylla -d scylladb/scylla --smp 1

This command will start a Scylla single-node cluster in developer mode (see --developer-mode 1) limited by a single CPU core (see --smp). Production grade configuration requires tuning a few kernel parameters such that limiting number of available cores (with --smp 1) is the simplest way to go.

Multiple cores requires setting a proper value to the /proc/sys/fs/aio-max-nr. On many non production systems it will be equal to 65K. The formula to calculate proper value is:

Available AIO on the system - (request AIO per-cpu * ncpus) =
aio_max_nr - aio_nr < (reactor::max_aio + detect_aio_poll + reactor_backend_aio::max_polls) * cpu_cores =
aio_max_nr - aio_nr < (1024 + 2 + ***) * cpu_cores =
aio_max_nr - aio_nr < *** * cpu_cores

where

reactor::max_aio = max_aio_per_queue * max_queues,
max_aio_per_queue = 128,
max_queues = 8.

How to use this image

Start a scylla server instance

console
$ docker run --name some-scylla --hostname some-scylla -d scylladb/scylla

Run nodetool utility

console
$ docker exec -it some-scylla nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address     Load       Tokens  Owns (effective)  Host ID                               Rack
UN  172.17.0.2  125.51 KB  256     100.0%            c9155121-786d-44f8-8667-a8b915b95665  rack1

Run cqlsh utility

console
$ docker exec -it some-scylla cqlsh
Connected to Test Cluster at 172.17.0.2:9042.
[cqlsh 5.0.1 | Cassandra 2.1.8 | CQL spec 3.2.1 | Native protocol v3]
Use HELP for help.
cqlsh>

Make a cluster

console
$ docker run --name some-scylla2  --hostname some-scylla2 -d scylladb/scylla --seeds="$(docker inspect --format='{{ .NetworkSettings.IPAddress }}' some-scylla)"

Make a cluster with Docker Compose

First, create a docker-compose.yml file with the following contents:

yaml
version: '3'

services:
  some-scylla:
    image: scylladb/scylla
    container_name: some-scylla

  some-scylla2:
    image: scylladb/scylla
    container_name: some-scylla2
    command: --seeds=some-scylla

  some-scylla3:
    image: scylladb/scylla
    container_name: some-scylla3
    command: --seeds=some-scylla

Then, launch the 3-node cluster as follows:

docker-compose up -d

Check scylla logs

console
$ docker logs some-scylla | tail
INFO  2016-08-04 06:57:40,836 [shard 5] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,836 [shard 3] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,836 [shard 1] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,836 [shard 2] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,836 [shard 4] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,836 [shard 7] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,837 [shard 6] database - Setting compaction strategy of system_traces.events to SizeTieredCompactionStrategy
INFO  2016-08-04 06:57:40,839 [shard 0] database - Schema version changed to fea14d93-9c5a-34f5-9d0e-2e49dcfa747e
INFO  2016-08-04 06:57:40,839 [shard 0] storage_service - Starting listening for CQL clients on 172.17.0.2:9042...
INFO  2016-08-04 06:57:40,840 [shard 0] storage_service - Thrift server listening on 172.17.0.2:9160 ...

Configuring data volume for storage

You can use Docker volumes to improve performance of Scylla.

Create a Scylla data directory /var/lib/scylla on the host, which is used by Scylla container to store all data:

console
$ sudo mkdir -p /var/lib/scylla/data /var/lib/scylla/commitlog /var/lib/scylla/hints /var/lib/scylla/view_hints

Launch Scylla using Docker's --volume command line option to mount the created host directory as a data volume in the container and disable Scylla's developer mode to run I/O tuning before starting up the Scylla node.

console
$ docker run --name some-scylla --volume /var/lib/scylla:/var/lib/scylla -d scylladb/scylla --developer-mode=0

Configuring resource limits

The Scylla docker image defaults to running on overprovisioned mode and won't apply any CPU pinning optimizations, which it normally does in non-containerized environments. For better performance, it is recommended to configure resource limits for your Docker container using the --smp, --memory, and --cpuset command line options, as well as disabling the overprovisioned flag as documented in the section "Command-line options".

Restart Scylla

The Docker image uses supervisord to manage Scylla processes. You can restart Scylla in a Docker container using

docker exec -it some-scylla supervisorctl restart scylla

Command-line options

The Scylla image supports many command line options that are passed to the docker run command.

--seeds SEEDS

The -seeds command line option configures Scylla's seed nodes. If no --seeds option is specified, Scylla uses its own IP address as the seed.

For example, to configure Scylla to run with two seed nodes 192.168.0.100 and 192.168.0.200.

console
$ docker run --name some-scylla -d scylladb/scylla --seeds 192.168.0.100,192.168.0.200

--listen-address ADDR

The --listen-address command line option configures the IP address the Scylla instance listens on for connections from other Scylla nodes.

For example, to configure Scylla to use listen address 10.0.0.5:

console
$ docker run --name some-scylla -d scylladb/scylla --listen-address 10.0.0.5

--alternator-address ADDR

The --alternator-address command line option configures the Alternator API listen address. The default value is the same as --listen-address.

--alternator-port PORT

The --alternator-port command line option configures the Alternator API listen port. The Alternator API is disabled by default. You need to specify the port to enable it.

For example, to configure Scylla to listen to Alternator API at port 8000:

console
$ docker run --name some-scylla -d scylladb/scylla --alternator-port 8000

--alternator-https-port PORT

The --alternator-https-port option is similar to --alternator-port, just enables an encrypted (HTTPS) port. Either the --alternator-https-port or --alternator-http-port, or both, can be used to enable Alternator.

Note that the --alternator-https-port option also requires that files /etc/scylla/scylla.crt and /etc/scylla/scylla.key be inserted into the image. These files contain an SSL certificate and key, respectively.

--alternator-write-isolation policy

The --alternator-write-isolation command line option chooses between four allowed write isolation policies described in docs/alternator/alternator.md. This option must be specified if Alternator is enabled - it does not have a default.

--broadcast-address ADDR

The --broadcast-address command line option configures the IP address the Scylla instance tells other Scylla nodes in the cluster to connect to.

For example, to configure Scylla to use broadcast address 10.0.0.5:

console
$ docker run --name some-scylla -d scylladb/scylla --broadcast-address 10.0.0.5

--broadcast-rpc-address ADDR

The --broadcast-rpc-address command line option configures the IP address the Scylla instance tells clients to connect to.

For example, to configure Scylla to use broadcast RPC address 10.0.0.5:

console
$ docker run --name some-scylla -d scylladb/scylla --broadcast-rpc-address 10.0.0.5

--smp COUNT

The --smp command line option restricts Scylla to COUNT number of CPUs. The option does not, however, mandate a specific placement of CPUs. See the --cpuset command line option if you need Scylla to run on specific CPUs.

For example, to restrict Scylla to 2 CPUs:

console
$ docker run --name some-scylla -d scylladb/scylla --smp 2

--memory AMOUNT

The --memory command line option restricts Scylla to use up to AMOUNT of memory. The AMOUNT value supports both M unit for megabytes and G unit for gigabytes.

For example, to restrict Scylla to 4 GB of memory:

console
$ docker run --name some-scylla -d scylladb/scylla --memory 4G

--reserve-memory AMOUNT

The --reserve-memory command line option configures Scylla to reserve the AMOUNT of memory to the OS. The AMOUNT value supports both M unit for megabytes and G unit for gigabytes.

For example, to reserve 4 GB of memory to the OS:

console
$ docker run --name some-scylla -d scylladb/scylla --reserve-memory 4G

--overprovisioned ENABLE

The --overprovisioned command line option enables or disables optimizations for running Scylla in an overprovisioned environment. If no --overprovisioned option is specified, Scylla defaults to running with optimizations enabled. If --overprovisioned is not specified and is left at its default, specifying --cpuset will automatically disable --overprovisioned

For example, to enable optimizations for running in an statically partitioned environment:

console
$ docker run --name some-scylla -d scylladb/scylla --overprovisioned 0

--io-setup ENABLE

The --io-setup command line option specifies if the scylla_io_setup script is run when the container is started for the first time. This is useful if users want to specify I/O settings themselves in environments such as Kubernetes, where running iotune is problematic. The default of --io-setup is 1, which means I/O setup is run.

For example, to skip running I/O setup:

console
$ docker run --name some-scylla -d scylladb/scylla --io-setup 0

--cpuset CPUSET

The --cpuset command line option restricts Scylla to run on only on CPUs specified by CPUSET. The CPUSET value is either a single CPU (e.g. --cpuset 1), a range (e.g. --cpuset 2-3), or a list (e.g. --cpuset 1,2,5), or a combination of the last two options (e.g. --cpuset 1-2,5).

For example, to restrict Scylla to run on physical CPUs 0 to 2 and 4:

console
$ docker run --name some-scylla -d scylladb/scylla --cpuset 0-2,4

--developer-mode ENABLE

The --developer-mode command line option enables Scylla's developer mode, which relaxes checks for things like XFS and enables Scylla to run on unsupported configurations (which usually results in suboptimal performance). If no --developer-mode command line option is defined, Scylla defaults to running with developer mode enabled. It is highly recommended to disable developer mode for production deployments to ensure Scylla is able to run with maximum performance.

For example, to disable developer mode:

console
$ docker run --name some-scylla -d scylladb/scylla --developer-mode 0

--experimental ENABLE

The --experimental command line option enables Scylla's experimental mode If no --experimental command line option is defined, Scylla defaults to running with experimental mode disabled. It is highly recommended to disable experimental mode for production deployments.

For example, to enable experimental mode:

console
$ docker run --name some-scylla -d scylladb/scylla --experimental 1

--disable-version-check

The --disable-version-check disable the version validation check.

--authenticator AUTHENTICATOR

The --authenticator command lines option allows to provide the authenticator class Scylla will use. By default Scylla uses the AllowAllAuthenticator which performs no credentials checks. The second option is using the PasswordAuthenticator parameter, which relies on username/password pairs to authenticate users.

--authorizer AUTHORIZER

The --authorizer command lines option allows to provide the authorizer class Scylla will use. By default Scylla uses the AllowAllAuthorizer which allows any action to any user. The second option is using the CassandraAuthorizer parameter, which stores permissions in system_auth.permissions table.

JMX parameters

JMX Scylla service is initialized from the /scylla-jmx-service.sh on container startup. By default the script uses /etc/sysconfig/scylla-jmx to read default configuration. It then can be overridden by setting an environmental parameters.

An example:

docker run -d -e "SCYLLA_JMX_ADDR=-ja 0.0.0.0" -e SCYLLA_JMX_REMOTE=-r --publish 7199:7199 scylladb/scylla

SCYLLA_JMX_PORT

Scylla JMX listening port.

Default value:

SCYLLA_JMX_PORT="-jp 7199"

SCYLLA_API_PORT

Scylla API port for JMX to connect to.

Default value:

SCYLLA_API_PORT="-p ***"

SCYLLA_API_ADDR

Scylla API address for JMX to connect to.

Default value:

SCYLLA_API_ADDR="-a localhost"

SCYLLA_JMX_ADDR

JMX address to bind on.

Default value:

SCYLLA_JMX_ADDR="-ja localhost"

For example, it is possible to make JMX available to the outer world by changing its bind address to 0.0.0.0:

docker run -d -e "SCYLLA_JMX_ADDR=-ja 0.0.0.0" -e SCYLLA_JMX_REMOTE=-r --publish 7199:7199 scylladb/scylla

cassandra-stress requires direct access to the JMX.

SCYLLA_JMX_FILE

A JMX service configuration file path.

Example value:

SCYLLA_JMX_FILE="-cf /etc/scylla.d/scylla-user.cfg"

SCYLLA_JMX_LOCAL

The location of the JMX executable.

Example value:

SCYLLA_JMX_LOCAL="-l /opt/scylladb/jmx

SCYLLA_JMX_REMOTE

Allow JMX to run remotely.

Example value:

SCYLLA_JMX_REMOTE="-r"

SCYLLA_JMX_DEBUG

Enable debugger.

Example value:

SCYLLA_JMX_DEBUG="-d"

Related Links

• http://docs.scylladb.com/procedures/best_practices_scylla_on_docker/

User Feedback

Issues

For bug reports, please use Scylla's https://github.com/scylladb/scylla/issues on GitHub. Please read the http://docs.scylladb.com/operating-scylla/troubleshooting/report_scylla_problem/ page before you report bugs.

For general help, see Scylla's http://www.scylladb.com/doc/. For questions and comments, use Scylla's http://www.scylladb.com/community/.

Contributing

Want to scratch your own itch and contribute a patch. We are eager to review and merge your code. Please consult the http://www.scylladb.com/kb/contributing/