Updates Sigv4 signer to only cache up to 50 service clients at a time

Author: chrisradek

lib/signers/v4.js

@@ -6,6 +6,16 @@ var inherit = AWS.util.inherit;
  */
 var cachedSecret = {};
 
+/**
+ * @api private
+ */
+var cacheQueue = [];
+
+/**
+ * @api private
+ */
+var maxCacheEntries = 50;
+
 /**
  * @api private
  */
@@ -100,6 +110,15 @@ AWS.Signers.V4 = inherit(AWS.Signers.RequestSigner, {
     var cacheIdentifier = this.serviceName + (this.getServiceClientId() ? '_' + this.getServiceClientId() : '');
     if (this.signatureCache) {
       var cache = cachedSecret[cacheIdentifier];
+      // If there isn't already a cache entry, we'll be adding one
+      if (!cache) {
+        cacheQueue.push(cacheIdentifier);
+        if (cacheQueue.length > maxCacheEntries) {
+          // remove the oldest entry (may not be last one used)
+          delete cachedSecret[cacheQueue.shift()];
+        }
+      }
+
     }
     var date = datetime.substr(0, 8);
 

test/signers/v4.spec.coffee

@@ -84,7 +84,25 @@ describe 'AWS.Signers.V4', ->
         calls = AWS.util.crypto.hmac.calls
         callCount = calls.length
 
-
+      it 'will cache a maximum of 50 clients', (done) ->
+        maxCacheEntries = 50
+        clientSigners = (buildSignerFromService() for i in [0..maxCacheEntries-1])
+        callCount = calls.length
+        #Get signature for all clients to store them in cache
+        (clientSigners[i].signature(creds, datetime) for i in [0..clientSigners.length-1])
+        expect(calls.length).to.equal(callCount + (5 * maxCacheEntries))
+        #Signer should use cache
+        callCount = calls.length
+        clientSigners[0].signature(creds, datetime)
+        expect(calls.length).to.equal(callCount + 1)
+        #add a new signer, pushing past cache limit
+        newestSigner = buildSignerFromService()
+        #old signer shouldn't be using cache anymore
+        callCount = calls.length
+        clientSigners[0].signature(creds, datetime)
+        expect(calls.length).to.equal(callCount + 5)
+        done()
+        
       #Calling signer.signature should call hmac 1 time when caching, and 5 times when not caching
       it 'caches subsequent requests', ->
         signer.signature(creds, datetime)