serve favicons over hashed paths for improved caching

lib/servers.js

@@ -1,3 +1,5 @@
+const crypto = require('crypto')
+
 const TimeTracker = require('./time')
 
 const config = require('../config')
@@ -61,11 +63,8 @@ class ServerRegistration {
         update.recordData = this.recordData
       }
 
-      // Compare against this.data.favicon to support favicon overrides
-      const newFavicon = resp.favicon || this.data.favicon
-      if (this.updateFavicon(newFavicon)) {
-        // Append an updated favicon
-        update.favicon = newFavicon
+      if (this.updateFavicon(resp.favicon)) {
+        update.favicon = this.getFaviconUrl()
       }
 
       // Append a result object
@@ -101,7 +100,7 @@ class ServerRegistration {
       const payload = {
         versions: this.versions,
         recordData: this.recordData,
-        favicon: this.lastFavicon
+        favicon: this.getFaviconUrl()
       }
 
       // Only append graphPeakData if defined
@@ -134,7 +133,8 @@ class ServerRegistration {
         message: 'Pinging...'
       },
       recordData: this.recordData,
-      graphPeakData: this.getGraphPeak()
+      graphPeakData: this.getGraphPeak(),
+      favicon: this.data.favicon
     }
   }
 
@@ -216,13 +216,35 @@ class ServerRegistration {
   }
 
   updateFavicon (favicon) {
+    // If data.favicon is defined, then a favicon override is present
+    // Disregard the incoming favicon, regardless if it is different
+    if (this.data.favicon) {
+      return false
+    }
+
     if (favicon && favicon !== this.lastFavicon) {
       this.lastFavicon = favicon
+
+      // Generate an updated hash
+      // This is used by #getFaviconUrl
+      if (!this._faviconHasher) {
+        this._faviconHasher = crypto.createHash('md5')
+      }
+      this.faviconHash = this._faviconHasher.update(favicon).digest('hex').toString()
+
       return true
     }
     return false
   }
 
+  getFaviconUrl () {
+    if (this.faviconHash) {
+      return '/hashedfavicon?' + this.faviconHash
+    } else if (this.data.favicon) {
+      return this.data.favicon
+    }
+  }
+
   updateProtocolVersionCompat (incomingId, outgoingId, protocolIndex) {
     // If the result version matches the attempted version, the version is supported
     const isSuccess = incomingId === outgoingId