Add ability to pass ignoreErrors to the configuration options.

When ignoreErrors is true, if an error is encountered connecting to redis the next() middleware is called.

README.md

@@ -46,6 +46,8 @@ limiter(options)
  - `expire`: `Number` amount of time in `ms` before the rate-limited is reset
  - `whitelist`: `function(req)` optional param allowing the ability to whitelist. return `boolean`, `true` to whitelist, `false` to passthru to limiter.
  - `skipHeaders`: `Boolean` whether to skip sending HTTP headers for rate limits ()
+ - `ignoreErrors`: `Boolean` whether errors generated from redis should allow the middleware to call next().  Defaults to false.
+
 ### Examples
 
 ``` js

index.js

@@ -12,6 +12,7 @@ module.exports = function (app, db) {
 
       var key = 'ratelimit:' + opts.path + ':' + opts.method + ':' + lookups
       db.get(key, function (err, limit) {
+        if (err && opts.ignoreErrors) return next()
         var now = Date.now()
         limit = limit ? JSON.parse(limit) : {
           total: opts.total,

tests/index.js

@@ -93,5 +93,28 @@ describe('rate-limiter', function () {
           .expect(function(res) { if ('Retry-After' in res.headers) return 'Retry-After not to be set' })
           .expect(429, done)
     })
+
+    it('should process ignoreErrors', function (done) {
+      limiter({
+        path: '/route',
+        method: 'get',
+        lookup: ['connection.remoteAddress'],
+        total: 10,
+        expire: 1000 * 60 * 60,
+        ignoreErrors: true
+      })
+
+      app.get('/route', function (req, res) {
+        res.send(200, 'hello')
+      })
+
+      sinon.stub(redis, 'get', function(key, callback) {
+        callback({err: true})
+      })
+
+      request(app)
+        .get('/route')
+          .expect(200, done)
+    })
   })
 })