docker-riak

This is a Docker project to bring up a local Riak cluster.

Prerequisites

Install Docker

Follow the instructions on Docker's website to install Docker.

Many (but not all) Docker environments set the DOCKER_HOST environment variable to help the client find the Docker host. Some environments use a Unix domain socket by default.

If your Docker client connects to the Docker host via TCP, ensure that your DOCKER_HOST environmental variable is set correctly:

$ export DOCKER_HOST="tcp://127.0.0.1:2375"

Note: If you're using boot2docker ensure that you forward the virtual machine port range (49000-49900). If you want to set DOCKER_RIAK_BASE_HTTP_PORT, ensure that you forward that port range instead:

$ for i in {49000..49900}; do
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port$i,tcp,,$i,,$i";
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "udp-port$i,udp,,$i,,$i";
done

sysctl

In order to tune the Docker host housing Riak containers, consider applying the following sysctl settings:

vm.swappiness = 0
net.ipv4.tcp_max_syn_backlog = 40000
net.core.somaxconn = 40000
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_fin_timeout = 15
net.ipv4.tcp_keepalive_intvl = 30
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_moderate_rcvbuf = 1

Running

Clone repository and build Riak image

$ git clone https://github.com/hectcastro/docker-riak.git
$ cd docker-riak
$ make build

Environmental variables

• DOCKER_RIAK_CLUSTER_SIZE – The number of nodes in your Riak cluster (default: 5)
• DOCKER_RIAK_AUTOMATIC_CLUSTERING – A flag to automatically cluster Riak (default: false)
• DOCKER_RIAK_DEBUG – A flag to set -x on the cluster management scripts (default: false)
• DOCKER_RIAK_BASE_HTTP_PORT - A flag to use fixed port assignment. If set, manually forward port DOCKER_RIAK_BASE_HTTP_PORT + $index to 8098 (Riak's HTTP port) and forward DOCKER_RIAK_BASE_HTTP_PORT + $index + DOCKER_RIAK_PROTO_BUF_PORT_OFFSET to 8087 (Riak's Protocol Buffers port).
• DOCKER_RIAK_PROTO_BUF_PORT_OFFSET - Optional port offset (default: 100)
• DOCKER_RIAK_BACKEND - Optional Riak backend to use (default: bitcask)
• DOCKER_RIAK_STRONG_CONSISTENCY - Enables strong consistency subsystem (values: on or off, default: off)
• DOCKER_RIAK_SEARCH - Enables search (values: on or off, default: off)

Launch cluster

$ DOCKER_RIAK_AUTOMATIC_CLUSTERING=1 DOCKER_RIAK_CLUSTER_SIZE=5 DOCKER_RIAK_BACKEND=leveldb make start-cluster
./bin/start-cluster.sh

Bringing up cluster nodes:

Starting riak01..... Completed
Starting riak02..... Completed
Starting riak03..... Completed
Starting riak04..... Completed
Starting riak05..... Completed

Please wait approximately 30 seconds for the cluster to stabilize.

Testing

From outside the container, we can interact with the HTTP or Protocol Buffers interfaces.

HTTP

The HTTP interface has an endpoint called /stats that emits Riak statistics. The test-cluster Makefile target hits a random container's /stats endpoint and pretty-prints its output to the console.

The most interesting attributes for testing cluster membership are ring_members:

$ make test-cluster | egrep -A6 "ring_members"
    "ring_members": [
        "riak@172.17.0.2",
        "riak@172.17.0.3",
        "riak@172.17.0.4",
        "riak@172.17.0.5",
        "riak@172.17.0.6"
    ],

And ring_ownership:

$ make test-cluster | egrep "ring_ownership"
    "ring_ownership": "[{'riak@172.17.0.20',3},\n {'riak@172.17.0.10',4},\n {'riak@172.17.0.21',3},\n {'riak@172.17.0.11',4},\n {'riak@172.17.0.2',3},\n {'riak@172.17.0.12',4},\n {'riak@172.17.0.3',3},\n {'riak@172.17.0.13',4},\n {'riak@172.17.0.4',3},\n {'riak@172.17.0.14',3},\n {'riak@172.17.0.5',3},\n {'riak@172.17.0.15',3},\n {'riak@172.17.0.6',3},\n {'riak@172.17.0.16',3},\n {'riak@172.17.0.7',3},\n {'riak@172.17.0.17',3},\n {'riak@172.17.0.8',3},\n {'riak@172.17.0.18',3},\n {'riak@172.17.0.9',3},\n {'riak@172.17.0.19',3}]",

Together, these attributes let us know that this particular Riak node knows about all of the other Riak instances.

SSH

The phusion/baseimage-docker image has the ability to enable an insecure key for conveniently logging into a container via SSH. It is enabled in the Dockerfile by default here:

RUN /usr/sbin/enable_insecure_key

In order to login to the container via SSH using the insecure key, follow the steps below.

Use docker inspect to determine the container IP address:

$ docker inspect $CONTAINER_ID | grep IPAddress
        "IPAddress": "172.17.0.2",

Download the insecure key, alter its permissions, and use it to SSH into the container via its IP address:

$ curl -o insecure_key -fSL https://github.com/phusion/baseimage-docker/raw/master/image/services/sshd/keys/insecure_key
$ chmod 600 insecure_key
$ ssh -i insecure_key root@172.17.0.2

Note: If you're using boot2docker, ensure that you're issuing the SSH command from within the virtual machine running boot2docker.

Stopping

$ make stop-cluster
./bin/stop-cluster.sh
Stopped all of the running containers.

Destroying

$ make remove-cluster
./bin/remove-cluster.sh
Stopped the cluster and cleared all of the running containers.