etcd playground

A safe place to experiment with etcd distributed key value store.

Description

This is a safe workspace and playground open to anyone looking to experiment with etcd distributed key value store. The environment targets dev/test usage and is not adviced to be used in production.

Dependencies

The workspace depneds on:

• etcd
• direnv
• goreman
• curl

What is etcd ?

"etcd is an open-source distributed key value store that provides shared configuration and service discovery for Container Linux clusters. etcd runs on each machine in a cluster and gracefully handles leader election during network partitions and the loss of the current leader"ref.

How to

Initialise the workspace

$ direnv allow 

Initialization will create the '${PWD}/bin/' folder and will download any required binaries e.g etcd, goreman etc.

Below there are some very basic tasks you may need to test against.

Start a single etcd server

$ etcd
2018-12-22 21:37:52.042182 I | etcdmain: etcd Version: ...

Start an etcd cluster

$ goreman start
goreman start                                                                                                                                   git:(master↓5↑2|✚2…
21:28:50 etcd2 | Starting etcd2 on port 5001                                                                                                                                                         
21:28:50 proxy | Starting proxy on port 5003                                                                                                                                                         
21:28:50 etcd1 | Starting etcd1 on port 5000                                                                                                                                                         
21:28:50 etcd3 | Starting etcd3 on port 5002 
...                                                                                        

NOTE: by default a three node cluster is spawn please advice procfile

Verify the server/cluster status

$ curl -L http://127.0.0.1:2379/health 
member 8211f1d0f64f3269 is healthy: got healthy result from http://127.0.0.1:3379
member 91bc3c398fb3c146 is healthy: got healthy result from http://127.0.0.1:4379
member fd422379fda50e48 is healthy: got healthy result from http://127.0.0.1:5379

Enumerate all cluster members

$ etcdctl member list 
8211f1d0f64f3269: name=infra1 peerURLs=http://127.0.0.1:12380 clientURLs=http://127.0.0.1:3379 isLeader=false
91bc3c398fb3c146: name=infra2 peerURLs=http://127.0.0.1:22380 clientURLs=http://127.0.0.1:4379 isLeader=false
fd422379fda50e48: name=infra3 peerURLs=http://127.0.0.1:32380 clientURLs=http://127.0.0.1:5379 isLeader=true

Verify clusters health

$ etcdctl cluster-health                                                                                                                           

Set the value of an example key

$ etcdctl set /key1 "value1"
value1

Retrieve example key value

$ etcdctl get /key1
value1

Delete example key

etcdctl rm /key1

Set the value of an example key using the HTTP-based API

$ curl -L -X PUT http://127.0.0.1:2379/v2/keys/key2 -d value="value2"

Retrive example key vaue using the HTTP-based API

$ curl -L http://127.0.0.1:2379/v2/keys/key2
{"action":"get","node":{"key":"/key2","value":"value2","modifiedIndex":19,"createdIndex":19}}

Create a directory

$ etcdctl mkdir /tdir 

Verify dir creation

$ etcdctl ls
/tdir

Create a timed key with 30 sec time-to-live

$ etcdctl mk /timedkey "It's going to expire in 30 sec" --ttl 30

Check afer a couple seconds and after 30 seconds using the command below:

$ etcdctl get /timedkey "It's going to expire in 30 sec" --ttl 30

References and links

• etcd
• etcd documentation (latest)
• Getting started with etcd
• etcd @ github
• goreman