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https://github.com/killme2008/lighthouse
leader election and node register/discover/balance in a service cluster by zookeeper in clojure
https://github.com/killme2008/lighthouse
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leader election and node register/discover/balance in a service cluster by zookeeper in clojure
- Host: GitHub
- URL: https://github.com/killme2008/lighthouse
- Owner: killme2008
- License: epl-1.0
- Created: 2015-05-19T06:08:21.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2015-07-30T08:53:45.000Z (over 9 years ago)
- Last Synced: 2024-04-14T16:06:36.039Z (7 months ago)
- Language: Clojure
- Homepage:
- Size: 156 KB
- Stars: 6
- Watchers: 4
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# lighthouse
A Clojure library designed to leader election and node register/discover/balance in a service cluster by zookeeper.
## Usage
Add dependency in your project:
```clj
[lighthouse "0.1.0"]
```
Create a [curator](http://curator.apache.org/) framework client:
```clj
(require '[lighthouse.zk :as zk])
(def cli (zk/mk-client "localhost:2181"))
```
### Service register/discover/balance
In a service node:
```clj
(require '[lighthouse.discover :refer :all])
;;register a node to zookeeper
(register cli "user-service")
```
Every service node can register itself to zookeeper by above code.
The default registerd node id and data is the node's machine hostname,but you can special them by:
```clj
(def node (register cli "user-service" :id "node-1" :data "192.168.1.20:8080"))
```
When you shutdown the node, you can unregister it by `(unregister node)`.
In a service consumer, you can create a balancer for `user-service`:
```clj
(require '[lighthouse.discover :refer :all])
(def user-service-balancer (create-service-balancer cli "user-service"))
```
Then You can get an alive `user-service` node:
```
(user-service-balancer)
```
It returns a node value map: `{:id "node-1" :data "192.168.1.20:8080"}`。
The default balance type is `:round-robin`,you can create other balancer type:
```
(def user-service-balancer (create-service-balancer cli "user-service" :balancer-type :random))
(def user-service-balancer (create-service-balancer cli "user-service" :balancer-type :hash))
```
When you use `:hash` strategy, you must pass a key to balancer for hashing:
```clj
(user-service-balancer "a")
(user-service-balancer "b")
;;pass a default value that returned when can not find an alive node.
(user-service-balancer "a" {:id "default-node" :data "node1.ip"})
```
Stop the balancer:
```clj
(stop-service-balancer user-service-balancer)
```
### Leader election
Every node trys to elect a leader:
```clj
(require '[lighthouse.leader :refer :all])
(start-election cli "/leader_election"
(fn [cli path id]
(println id "got leadership."))
(fn [cli path id]
(println id "released leadership."))
:id "node-1")
```
Each node pass it's id,if not present, the default id is the node's matchine hostname.
```clj
(start-election client path on-aquired on-released & {:keys [id]})
```
When the node got the leadership, the `on-aquired` would be called with curator client,path and itself id.
And when the node released the leadership, the `on-released` would be called with curator client,path and itself id.
The `start-election` returns a resettable promise, you can deliver it a true value to stop the election, or a false value to
release the leadership but still be in queue for next election:
```clj
(def p (start-election ......))
;;release the leadership,but still be in queue for next election
(deliver p false)
;;stop current node in election
(deliver p true)
```
When election starts, you can get current leader or participants:
```clj
(get-leader cli "/leader_election")
(get-participants cli "/leader_election")
```
Stop current node in election:
```
(stop)
```
## License
Copyright © 2015 dennis zhuang
Distributed under the Eclipse Public License either version 1.0 or (at
your option) any later version.