onedari

onedari

Onedari is simple service discovery.

Data Model

The data model is simple. There are three types of entities: nodes, instances, and services.

• nodes a "server"
• instances represent a single instance of an application. An instance has an address and a port associated with it. "belongs" to a node
• services represent a collection of instances. instances are associated with a service via label queries.

instances and services have labels. Labels are just key/value pairs (strings only) and have no inherent meaning to the system. A service has a query defined which is also key/value pairs. These are used to query the instances. Note: all query keys and values must match.

Label queries were inspired by Kubernetes.

Installation

git clone https://github.com/bakins/onedari.git
cd cmd/onedari
go get .
go build

onedari will now be in $GOPATH/bin

Modes

onedari is a single binary that implements the following "modes":

• server A simple, stateless HTTP API server. It uses etcd as its backing store. All other "modes" use this API - nothing else communicates with etcd
• dns A simple DNS server for a single (sub)domain.
• announce A helper used to "announce" a single instance.

All of these are lightweight and can be ran on every node. It is suggested to run an etcd proxy on every node as well.

Example

A quick example.

Assuming you have etcd running on localhost.

Start the server:

$ onedari server
time="2015-04-14T16:42:39-04:00" level=warning msg="truncating hostname leoben.local to leoben"

Now, use curl to see the node:

$ curl -s http://127.0.0.1:63412/v0/nodes
[{"id":"leoben","ip":"10.191.63.72"}]

Now, announce an instance of an app. While leaving the server running, do:

$ onedari announce foo
time="2015-04-14T16:44:44-04:00" level=warning msg="truncating hostname leoben.local to leoben"

Now, use curl to see the instance:

 curl -s http://127.0.0.1:63412/v0/instances
 [{"id":"leoben-foo","node":"leoben","labels":{"app":"foo"},"ip":"10.191.63.72","port":0,"target":"","up":true}]

Notice that it automatically added the label {"app":"foo"}.

Ctrl+C the announce. Now, let's add some additional labels:

$ onedari announce foo track=dev
time="2015-04-14T16:47:15-04:00" level=warning msg="truncating hostname leoben.local to leoben"

Now, curl the instance:

$ curl -s http://127.0.0.1:63412/v0/node/instances
[{"id":"leoben-foo","node":"leoben","labels":{"app":"foo","track":"dev"},"ip":"10.191.63.72","port":0,"target":"","up":true}]

Notice the additional label.

Now, add a service:

$ curl  -H "Content-Type: application/json" -svo /dev/null -X PUT --data-binary '{"labels":{"hello":"world"}, "query": {"app":"foo"}}'  http://127.0.0.1:63412/v0/services/foo

Using curl on /services will give us a summary view:

$ curl http://127.0.0.1:63412/v0/services
[{"id":"foo","labels":{"hello":"world"},"query":{"app":"foo"}}]

While, getting the actual service will give us the instances:

$ curl http://127.0.0.1:63412/v0/services/foo
{"id":"foo","labels":{"hello":"world"},"query":{"app":"foo"},"instances":[{"id":"leoben-foo","node":"leoben","labels":{"app":"foo","track":"dev"},"ip":"10.191.63.72","port":0,"target":"","up":true}]}

Notice that the instance we created earlier is associated with the service via the label {"app":"foo"}} that we set as the query for the service.

We can also query instances by label as well:

$ curl -s http://127.0.0.1:63412/v0/node/instances?track=dev
[{"id":"leoben-foo","node":"leoben","labels":{"app":"foo","track":"dev"},"ip":"10.191.63.72","port":0,"target":"","up":true}]

 $ curl -s http://127.0.0.1:63412/v0/node/instances?track=prod
 []

We can also search "globally." /v0/node/ only gets/sets for instances associated with the local node. /v0/instances is across all nodes - this is effectively what the services use internally.

Server

DNS

Announce