Load barancer

CHANGELOG.md

@@ -2,6 +2,10 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+### Added
+- Load barancer
+
 ## [1.2.1] - 2016-05-21
 ### Fixed
 - Error on Login page renderer

README.md

@@ -154,14 +154,15 @@ Specify proxy routes by array in descending order of priority.
 
 Each of route is specified in an object consisting of the following keys:
 
-| key     | type            | description                                                                                   |
-|---------|-----------------|-----------------------------------------------------------------------------------------------|
-| host    | string          | Host name matcher                                                                             |
-| url     | string (regexp) | URL matcher. optional. e.g. `"^/foo/bar[0-9]+$"`                                              |
-| methods | array of string | Arrowed methods                                                                               |
-| app     | string          | Application ID                                                                                |
-| etcd    | string          | Key of the target address in etcd. Specified by `--env APP=<vlalue>` in [Connect](#Connect).  |
-| public  | boolean         | Set `true` to disable authentication. (Default: `false`)                                      |
+| key      | type            | description                                                                                   |
+|----------|-----------------|-----------------------------------------------------------------------------------------------|
+| host     | string          | Host name matcher                                                                             |
+| url      | string (regexp) | URL matcher. optional. e.g. `"^/foo/bar[0-9]+$"`                                              |
+| methods  | array of string | Arrowed methods                                                                               |
+| app      | string          | Application ID                                                                                |
+| etcd     | string          | Key of the target address in etcd. Specified by `--env APP=<vlalue>` in [Connect](#Connect).  |
+| public   | boolean         | Set `true` to disable authentication. (Default: `false`)                                      |
+| backends | number          | Set number of backend instances to enable load barancing. Set null or 0 to disable LB.         |
 
 Route configurations can be write under `route` key of [configuration file](#Configuration).
 
@@ -171,6 +172,10 @@ You have to register JSON value of route configurations into etcd to Live-Config
 $ docker exec -i etcd /etcdctl set /routes "$(cat /path/to/routes.json)"
 ```
 
+#### Load barancing
+Backend applications must be named `app-N` and registerd into etcd.
+N is an integral number from 1 on up.
+
 #### Example of `routes.json`
 ```json
 [
@@ -190,7 +195,8 @@ $ docker exec -i etcd /etcdctl set /routes "$(cat /path/to/routes.json)"
   {
     "host": "bar.b.example.com",
     "app": "b",
-    "etcd": "bar"
+    "etcd": "bar",
+    "backends": 3
   }
 ]
 ```

src/server/__tests__/test-router.js

@@ -28,6 +28,12 @@ describe('Router', () => {
             host: 'app2.example.com',
             etcd: 'app2',
         },
+        {
+            app: 'app4',
+            host: 'app4.example.com',
+            etcd: 'app4',
+            backends: 3,
+        },
     ];
 
     let etcd, router;
@@ -118,4 +124,20 @@ describe('Router', () => {
                 expect(route).toEqual(routes[1]);
             });
     });
+
+    pit('routes as loadbarancer', () => {
+        Math.random = jest.fn().mockReturnValue((3.2 - 1) / 3);
+
+        etcd.get.mockReturnValueOnce(
+            Promise.resolve({ value: 'http://etcd-target-app4.example.com' })
+        );
+
+        return router.route('app4.example.com', '/', 'GET').then((route) => {
+                expect(route).toEqual({
+                    ...routes[4],
+                    target: 'http://etcd-target-app4.example.com',
+                });
+                expect(etcd.get).toBeCalledWith('backends/app4-3', true);
+            });
+    });
 });

src/server/router.js

@@ -44,7 +44,11 @@ export class Router {
                     return route;
                 }
 
-                return this.etcd.get(`backends/${route.etcd}`, true)
+                const n = route.backends &&
+                    Math.floor(Math.random() * route.backends) + 1;
+                const backend = n ? `${route.etcd}-${n}` : route.etcd;
+
+                return this.etcd.get(`backends/${backend}`, true)
                     .then((node) => ({
                         ...route,
                         target: node.value,