Cassandra on Docker

This is a collection of images and scripts to help you run Cassandra in Docker containers. These images are great to provision ephemeral Cassandra topologies for testing and development purpose.

Currently supported:
- A single Cassandra node
- A client container to run tools such as cqlsh, nodetool, etc.
- A multi-node cluster - running on a single Docker host
- Monitored cluster using OpsCenter
Work in progress:
- A small cluster for production - running on multiple Docker hosts
  - The missing puzzle piece here is how to expose Cassandra on the real outside network so that peers running on different hosts can connect.

If you'd like to help, please get in touch with me, and/or send me pull requests.

Prerequisites

A host running Docker - See https://www.docker.io/gettingstarted/#h_installation
You need to be able to run the docker command successfully as the currently logged in user. For example:
```
  $ docker version
  Client version: 0.7.4
```
...
If you're running as a user that can't run docker, add yourself to the docker group, or checkout out the project as root before you proceed. sudo might work too.

Build the docker and opscenter images (optional)

  ./cassandra/build.sh
  ./opscenter/build.sh

The last step is optional because Docker will automatically pull the images from index.docker.io if you don't already have them. The build process needs an Internet connection, but it is executed only once and then cached on Docker. If you modify the scripts, this is how you can re-build the images with your changes.

Single Cassandra node

Launch a server called cass1:
```
 docker run -d -name cass1 poklet/cassandra
```
You can also add the -p 9042:9042 option to bind container's 9042 port (CQL / native transport port) to host's 9042 port.

Connect to it using cqlsh:

 docker run -i -t poklet/cassandra cqlsh $(./scripts/ipof.sh cass1)

You should see something like:

Connected to Test Cluster at 172.17.0.25:9160.
[cqlsh 4.1.0 | Cassandra 2.0.3 | CQL spec 3.1.1 | Thrift protocol 19.38.0]
Use HELP for help.
cqlsh>

3-node Cassandra cluster

Launch three containers:

 docker run -d -name cass1 poklet/cassandra start
 docker run -d -name cass2 poklet/cassandra start $(./scripts/ipof.sh cass1)
 docker run -d -name cass3 poklet/cassandra start $(./scripts/ipof.sh cass1)
 # and so on...

The start script is passed the list of seeds - in this case, just the cass1's IP

Connect to it using nodetool:

 docker run -i -t poklet/cassandra nodetool -h $(./scripts/ipof.sh cass1) status

Create some data on the first container:

Launch cqlsh:

 docker run -i -t poklet/cassandra cqlsh $(./scripts/ipof.sh cass1)

Paste this in:

 create keyspace demo with replication = {'class':'SimpleStrategy', 'replication_factor':2};
 use demo;
 create table names ( id int primary key, name text );
 insert into names (id,name) values (1, 'gibberish');
 quit

Connect to the second container, and check if it can see your data:

Start up cqlsh (on cass2 this time):

 docker run -i -t poklet/cassandra cqlsh $(./scripts/ipof.sh cass2)

Paste in:

 select * from demo.names;

You should see:

 cqlsh> select * from demo.names;

  id | name
 ----+-----------
   1 | gibberish

 (1 rows)

10-node Cassandra cluster (scripted!)

Right, lets dive right in with some shell scripts in the scripts directory to help us:
```
 ./scripts/run.sh 10
```

That will start 10 nodes. Lets see what they're called:

 ./scripts/ips.sh

 172.17.0.10 cass6
 172.17.0.12 cass4
 172.17.0.11 cass5
 172.17.0.6 cass10
 172.17.0.7 cass9
 172.17.0.9 cass7
 172.17.0.8 cass8
 172.17.0.4 cass2
 172.17.0.3 cass3
 172.17.0.2 cass1

Same, but with the nodetool:

 ./scripts/nodetool.sh cass1 status

 Datacenter: datacenter1
 =======================
 Status=Up/Down
 |/ State=Normal/Leaving/Joining/Moving
 --  Address      Load       Tokens  Owns (effective)  Host ID                               Rack
 UN  172.17.0.11  74.19 KB   256     21.4%             dfd44ca5-bf73-4487-bcb2-db882d0a9231  rack1
 UN  172.17.0.10  74.21 KB   256     19.6%             f479a4e6-55ac-4533-8ce5-d137a93f2cc4  rack1
 UN  172.17.0.9   74.34 KB   256     20.4%             0bb389a0-f111-459c-9620-0faccc75cbc0  rack1
 UN  172.17.0.8   74.19 KB   256     20.1%             2eb4a4dd-2bbc-46a3-9f64-4e761509307d  rack1
 UN  172.17.0.12  74.14 KB   256     20.2%             a2547289-0c6a-458f-b982-823711c5293e  rack1
 UN  172.17.0.3   74.19 KB   256     20.3%             3667cc1a-1f63-4cd1-bebc-841f428a0f4d  rack1
 UN  172.17.0.2   74.24 KB   256     20.3%             2b48c8ac-ad68-48a0-9c41-c8f2fb7f38e6  rack1
 UN  172.17.0.7   67.7 KB    256     19.2%             e361f6d8-28ef-4cf8-baa1-88c2d1fec094  rack1
 UN  172.17.0.6   74.15 KB   256     19.6%             230f13b1-a27b-44e8-9b51-5ebdb1c4cb13  rack1
 UN  172.17.0.4   74.18 KB   256     18.8%             6c90cbaa-e5b3-41de-a160-3ecaf59b8856  rack1

When you're tired of your cluster, nuke them with:
```
 ./scripts/nuke.sh 10
```

Cassandra cluster + OpsCenter monitoring

Start a Cassandra cluster with 3 nodes:
```
 ./scripts/run.sh 3
```
Start the OpsCenter container:
```
 docker run -d -name opscenter poklet/opscenter
```
You can also add the -p 8888:8888 option to bind container's 8888 port to host's 8888 port
Connect and configure OpsCenter:
- Open a browser and connect to http://replace.me:8888 - replace the host by the result returned by ./scripts/ipof.sh opscenter.
- Click on the "Use Existing Cluster" button and put at least the IP of one node in the cluster in the host text box. The result of ./scripts/ipof.sh cass1 is a good candidate. Click "Save Cluster" button. OpsCenter start gathering data from the cluster but you do not get full-set metrics yet.
- You should see a "0 of 3 agents connected" message on the top of the GUI. Click the "Fix" link aside.
- In the popup, click "Enter Credentials" link and fill form with username opscenter and password opscenter. Click "Done".
- Click "Install on all nodes" and then "Accept Fingerprints". OpsCenter installs agent on cluster'snodes remotly.
- Once done, you should see the "All agents connected" message.