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Showing posts from March, 2015

ETCD: POST vs. PUT understanding

ETCD is distributed key value store used as a core component in CoreOS. I've already send a post earlier this week. Here is a page describing how to use ETCD basic commands = ETCD API. Code snippets placed in a page mostly use put, but ETCD allows to use post as well. Most of us understand differences between those two commands in a notion of a REST(ful) service, but how does it work in key value store?

POSTExample over many words.

curl -v http://127.0.0.1:2379/v2/keys/test -XPOST -D value="some value"
curl -v http://127.0.0.1:2379/v2/keys/test -XPOST -D value="some value"
Two same command result into following content:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23{ "action": "get", "node": { "key": "/test", "dir": true, "nodes": [ { "key": "/test/194", "value": "", "modifiedIndex"…

Playing with ETCD cluster in Docker on Local

I've started to write some management component last week. We would like to utilize CoreOs with the whole stack, as much as possible, at least within such early phase of our project.

The core component of our solution is ETCD - distributed key value store. Something like my favorite piece of software - Redis. Word 'distributed' means that the core of all things within your solution needs to be synchronized or 'consensused'. ETCD uses Raft. I'd love to know how my desired component works in real environment where everything can die.

In the age of docker - where every piece of software is docker-ized, it's pretty simple to start ETCD cluster on local in a second. Following piece of code starts three etcd instances linked together in one cluster.

docker run -d -p 4001:4001 -p 2380:2380 -p 2379:2379 --net=host --name etcd0 quay.io/coreos/etcd:v2.0.3 \
 -name etcd0 \
 -advertise-client-urls http://localhost:2379,http://localhost:4001 \
 -listen-client-urls http://lo…