Reconnect exponential backoff

HISTORY.md

@@ -1,3 +1,9 @@
+# [1.1.0](https://github.com/dpatty/eventsource/compare/v1.0.8...v1.1.0)
+* Allow configuring of the reconnection interval using an exponential backoff ([#126](https://github.com/EventSource/eventsource/pull/126) David Patty)
+
+# [1.0.8](https://github.com/dpatty/eventsource/compare/v1.0.7...v1.0.8)
+* Prevent simultaneous reconnection attempts on multiple errors ([#125](https://github.com/EventSource/eventsource/pull/125) David Patty)
+
 # [1.0.7](https://github.com/EventSource/eventsource/compare/v1.0.6...v1.0.7)
 
 * Add dispatchEvent to EventSource ([#101](https://github.com/EventSource/eventsource/pull/101) Ali Afroozeh)

lib/eventsource.js

@@ -44,7 +44,7 @@ function EventSource (url, eventSourceInitDict) {
   })
 
   var self = this
-  self.reconnectInterval = 1000
+  self.reconnectInterval = startingReconnectInterval
   self.connectionInProgress = false
 
   function onConnectionClosed (message) {
@@ -65,6 +65,13 @@ function EventSource (url, eventSourceInitDict) {
       self.connectionInProgress = true
       connect()
     }, self.reconnectInterval)
+
+    increaseReconnectInterval()
+  }
+
+  function increaseReconnectInterval () {
+    self.reconnectInterval *= reconnectIntervalBackoffMultiple
+    self.reconnectInterval = Math.min(maxReconnectInterval, self.reconnectInterval)
   }
 
   var req
@@ -133,7 +140,9 @@ function EventSource (url, eventSourceInitDict) {
     }
 
     req = (isSecure ? https : http).request(options, function (res) {
+      // release the lock on making connections
       self.connectionInProgress = false
+
       // Handle HTTP errors
       if (res.statusCode === 500 || res.statusCode === 502 || res.statusCode === 503 || res.statusCode === 504) {
         _emit('error', new Event('error', {status: res.statusCode, message: res.statusMessage}))
@@ -160,6 +169,9 @@ function EventSource (url, eventSourceInitDict) {
       }
 
       readyState = EventSource.OPEN
+      // reset reconnect interval now that we've actually made a connection
+      self.reconnectInterval = startingReconnectInterval
+
       res.on('close', function () {
         res.removeAllListeners('close')
         res.removeAllListeners('end')
@@ -351,6 +363,25 @@ EventSource.prototype.close = function () {
   this._close()
 }
 
+// set defaults to 30s max, and exponentially back off @ 2^n
+var startingReconnectInterval = 1000
+var maxReconnectInterval = 1000 * 30
+var reconnectIntervalBackoffMultiple = 2
+// setMaxReconnectInterval allows consumers to configure the max reconnect interval, and the backoff
+EventSource.prototype.setupReconnectInterval = function (starting, max, multiple) {
+  if (Number.isInteger(starting) && starting >= 0) {
+    startingReconnectInterval = starting
+  }
+  if (Number.isInteger(max) && max >= 0) {
+    maxReconnectInterval = max
+  }
+  if (Number.isFinite(multiple) && multiple > 0) {
+    reconnectIntervalBackoffMultiple = multiple
+  }
+
+  this.reconnectInterval = startingReconnectInterval
+}
+
 /**
  * Emulates the W3C Browser based WebSocket interface using addEventListener.
  *

package.json

@@ -1,7 +1,8 @@
 {
   "name": "eventsource2",
-  "version": "1.0.8",
-  "description": "W3C compliant EventSource client for Node.js and browser (polyfill). Forked from http://github.com/EventSource/eventsource",
+  "version": "1.1.0",
+  "description": "W3C compliant EventSource client for Node.js and browser (polyfill) Forked from http://github.com/EventSource/eventsource",
+
   "keywords": [
     "eventsource",
     "http",

test/eventsource_test.js

@@ -646,7 +646,7 @@ describe('HTTPS Client Certificate Support', function () {
 describe('Reconnection', function () {
   it('is attempted when server is down', function (done) {
     var es = new EventSource('http://localhost:' + _port)
-    es.reconnectInterval = 0
+    es.setupReconnectInterval(0)
 
     es.onerror = function () {
       es.onerror = null
@@ -669,7 +669,7 @@ describe('Reconnection', function () {
 
       server.on('request', writeEvents(['data: hello\n\n']))
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onmessage = function (m) {
         assert.equal('hello', m.data)
@@ -701,7 +701,7 @@ describe('Reconnection', function () {
       })
 
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       var errored = false
 
@@ -732,7 +732,7 @@ describe('Reconnection', function () {
 
       server.on('request', writeEvents(['data: hello\n\n']))
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onmessage = function (m) {
         assert.equal('hello', m.data)
@@ -777,7 +777,7 @@ describe('Reconnection', function () {
       })
 
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onerror = function (e) {
         assert.equal(e.status, 204)
@@ -814,7 +814,7 @@ describe('Reconnection', function () {
       server.on('request', writeEvents(['id: 10\ndata: Hello\n\n']))
 
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onmessage = function () {
         server.close(function (err) {
@@ -854,7 +854,7 @@ describe('Reconnection', function () {
       server.on('request', writeEvents(['data: Hello\n\n']))
 
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onmessage = function () {
         server.close(function (err) {
@@ -885,7 +885,7 @@ describe('Reconnection', function () {
           var fn = writeEvents(events)
           fn(req, res)
           eventsSent++
-          // now cause a parse error!
+          // now cause a few errors
           fn(req, res)
           eventsSent++
         } else {
@@ -897,13 +897,64 @@ describe('Reconnection', function () {
 
       var es = new EventSource(server.url)
       assert.equal(EventSource.CONNECTING, es.readyState)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
       es.onerror = function (err) {
-        console.log(err);
         errorOccurred = !!(errorOccurred || err)
       }
     })
   })
+
+  it('should allow configurability of reconnect interval', function (done) {
+    createServer(function (err, server) {
+      if (err) return done(err)
+
+      server.on('request', function (req, res) {
+        res.writeHead(500)
+        res.end()
+      })
+
+      var es = new EventSource(server.url)
+      es.setupReconnectInterval(5, 60, 1.5)
+      assert.equal(es.reconnectInterval, 5)
+
+      var errored = false
+      es.onerror = function () {
+        if (errored) return
+        errored = true
+        server.close(function (err) {
+          if (err) return done(err)
+          assert.equal(es.reconnectInterval, 5 * 1.5)
+          done()
+        })
+      }
+    })
+  })
+
+  it('attempts to reconnect should increase the reconnect interval exponentially', function (done) {
+    createServer(function (err, server) {
+      if (err) return done(err)
+      var eventsSent = 0
+      server.on('request', function (req, res) {
+        if (eventsSent === 0) {
+          res.writeHead(500)
+          res.end()
+        }
+      })
+
+      var es = new EventSource(server.url)
+      es.setupReconnectInterval(5, 25, 10)
+      var errored = false
+      es.onerror = function () {
+        if (errored) return
+        errored = true
+        server.close(function (err) {
+          if (err) return done(err)
+          assert.equal(es.reconnectInterval, 25)
+          done()
+        })
+      }
+    })
+  })
 })
 
 describe('readyState', function () {
@@ -946,7 +997,7 @@ describe('readyState', function () {
 
       server.on('request', writeEvents([]))
       var es = new EventSource(server.url)
-      es.reconnectInterval = 0
+      es.setupReconnectInterval(0)
 
       es.onopen = function (m) {
         server.close(function (err) {