Cassandra预计阅读时间: 10 分钟
Apache Cassandra is an open-source distributed storage system.
GitHub repo: https://github.com/docker-library/cassandra
This content is imported from the official Docker Library docs, and is provided by the original uploader. You can view the Docker Store page for this repo at https://store.docker.com/images/cassandra.
Supported tags and respective
For detailed information about the published artifacts of each of the above supported tags (image metadata, transfer size, etc), please see the
repos/cassandra directory in the
docker-library/repo-info GitHub repo.
For more information about this image and its history, please see the relevant manifest file (
library/cassandra). This image is updated via pull requests to the
docker-library/official-images GitHub repo.
What is Cassandra?
Apache Cassandra is an open source distributed database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassandra offers robust support for clusters spanning multiple datacenters, with asynchronous masterless replication allowing low latency operations for all clients.
How to use this image
cassandra server instance
Starting a Cassandra instance is simple:
$ docker run --name some-cassandra -d cassandra:tag
some-cassandra is the name you want to assign to your container and
tag is the tag specifying the Cassandra version you want. See the list above for relevant tags.
Connect to Cassandra from an application in another Docker container
This image exposes the standard Cassandra ports (see the Cassandra FAQ), so container linking makes the Cassandra instance available to other application containers. Start your application container like this in order to link it to the Cassandra container:
$ docker run --name some-app --link some-cassandra:cassandra -d app-that-uses-cassandra
Make a cluster
Using the environment variables documented below, there are two cluster scenarios: instances on the same machine and instances on separate machines. For the same machine, start the instance as described above. To start other instances, just tell each new node where the first is.
$ docker run --name some-cassandra2 -d -e CASSANDRA_SEEDS="$(docker inspect --format='' some-cassandra)" cassandra:tag
some-cassandra is the name of your original Cassandra Server container, taking advantage of
docker inspect to get the IP address of the other container.
Or you may use the docker run –link option to tell the new node where the first is:
$ docker run --name some-cassandra2 -d --link some-cassandra:cassandra cassandra:tag
For separate machines (ie, two VMs on a cloud provider), you need to tell Cassandra what IP address to advertise to the other nodes (since the address of the container is behind the docker bridge).
Assuming the first machine’s IP address is
10.42.42.42 and the second’s is
10.43.43.43, start the first with exposed gossip port:
$ docker run --name some-cassandra -d -e CASSANDRA_BROADCAST_ADDRESS=10.42.42.42 -p 7000:7000 cassandra:tag
Then start a Cassandra container on the second machine, with the exposed gossip port and seed pointing to the first machine:
$ docker run --name some-cassandra -d -e CASSANDRA_BROADCAST_ADDRESS=10.43.43.43 -p 7000:7000 -e CASSANDRA_SEEDS=10.42.42.42 cassandra:tag
Connect to Cassandra from
The following command starts another Cassandra container instance and runs
cqlsh (Cassandra Query Language Shell) against your original Cassandra container, allowing you to execute CQL statements against your database instance:
$ docker run -it --link some-cassandra:cassandra --rm cassandra sh -c 'exec cqlsh "$CASSANDRA_PORT_9042_TCP_ADDR"'
… or (simplified to take advantage of the
/etc/hosts entry Docker adds for linked containers):
$ docker run -it --link some-cassandra:cassandra --rm cassandra cqlsh cassandra
some-cassandra is the name of your original Cassandra Server container.
More information about the CQL can be found in the Cassandra documentation.
Container shell access and viewing Cassandra logs
docker exec command allows you to run commands inside a Docker container. The following command line will give you a bash shell inside your
$ docker exec -it some-cassandra bash
The Cassandra Server log is available through Docker’s container log:
$ docker logs some-cassandra
When you start the
cassandra image, you can adjust the configuration of the Cassandra instance by passing one or more environment variables on the
docker run command line.
This variable is for controlling which IP address to listen for incoming connections on. The default value is
auto, which will set the
listen_address option in
cassandra.yaml to the IP address of the container as it starts. This default should work in most use cases.
This variable is for controlling which IP address to advertise to other nodes. The default value is the value of
CASSANDRA_LISTEN_ADDRESS. It will set the
broadcast_rpc_address options in
This variable is for controlling which address to bind the thrift rpc server to. If you do not specify an address, the wildcard address (
0.0.0.0) will be used. It will set the
rpc_address option in
This variable is for controlling if the thrift rpc server is started. It will set the
start_rpc option in
This variable is the comma-separated list of IP addresses used by gossip for bootstrapping new nodes joining a cluster. It will set the
seeds value of the
seed_provider option in
CASSANDRA_BROADCAST_ADDRESS will be added the the seeds passed in so that the sever will talk to itself as well.
This variable sets the name of the cluster and must be the same for all nodes in the cluster. It will set the
cluster_name option of
This variable sets number of tokens for this node. It will set the
num_tokens option of
This variable sets the datacenter name of this node. It will set the
dc option of
This variable sets the rack name of this node. It will set the
rack option of
This variable sets the snitch implementation this node will use. It will set the
endpoint_snitch option of
Where to Store Data
Important note: There are several ways to store data used by applications that run in Docker containers. We encourage users of the
cassandra images to familiarize themselves with the options available, including:
- Let Docker manage the storage of your database data by writing the database files to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
- Create a data directory on the host system (outside the container) and mount this to a directory visible from inside the container. This places the database files in a known location on the host system, and makes it easy for tools and applications on the host system to access the files. The downside is that the user needs to make sure that the directory exists, and that e.g. directory permissions and other security mechanisms on the host system are set up correctly.
The Docker documentation is a good starting point for understanding the different storage options and variations, and there are multiple blogs and forum postings that discuss and give advice in this area. We will simply show the basic procedure here for the latter option above:
- Create a data directory on a suitable volume on your host system, e.g.
cassandracontainer like this:
$ docker run --name some-cassandra -v /my/own/datadir:/var/lib/cassandra -d cassandra:tag
-v /my/own/datadir:/var/lib/cassandra part of the command mounts the
/my/own/datadir directory from the underlying host system as
/var/lib/cassandra inside the container, where Cassandra by default will write its data files.
Note that users on host systems with SELinux enabled may see issues with this. The current workaround is to assign the relevant SELinux policy type to the new data directory so that the container will be allowed to access it:
$ chcon -Rt svirt_sandbox_file_t /my/own/datadir
No connections until Cassandra init completes
If there is no database initialized when the container starts, then a default database will be created. While this is the expected behavior, this means that it will not accept incoming connections until such initialization completes. This may cause issues when using automation tools, such as
docker-compose, which start several containers simultaneously.
Supported Docker versions
This image is officially supported on Docker version 17.04.0-ce.
Support for older versions (down to 1.6) is provided on a best-effort basis.
Please see the Docker installation documentation for details on how to upgrade your Docker daemon.
If you have any problems with or questions about this image, please contact us through a GitHub issue. If the issue is related to a CVE, please check for a
cve-tracker issue on the
official-images repository first.
You can also reach many of the official image maintainers via the
#docker-library IRC channel on Freenode.
You are invited to contribute new features, fixes, or updates, large or small; we are always thrilled to receive pull requests, and do our best to process them as fast as we can.
Before you start to code, we recommend discussing your plans through a GitHub issue, especially for more ambitious contributions. This gives other contributors a chance to point you in the right direction, give you feedback on your design, and help you find out if someone else is working on the same thing.
Documentation for this image is stored in the
cassandra/ directory of the
docker-library/docs GitHub repo. Be sure to familiarize yourself with the repository’s
README.md file before attempting a pull request.