caas: cache the creds, otherwise we bombard the server

src/storage/s3.js

@@ -44,12 +44,17 @@ function mockRestore() {
     AWS = originalAWS;
 }
 
-// TODO: If we decide to use rsync backups for CaaS, we should cache the credentials below
+var gCachedCaasCredentials = { issueDate: null, credentials: null };
+
 function getCaasCredentials(apiConfig, callback) {
     assert.strictEqual(typeof apiConfig, 'object');
     assert.strictEqual(typeof callback, 'function');
     assert(apiConfig.token);
 
+    if ((new Date() - gCachedCaasCredentials.issueDate) <= (1.75 * 60 * 60 * 1000)) { // caas gives tokens with 2 hour limit
+        return gCachedCaasCredentials.credentials;
+    }
+
     var url = config.apiServerOrigin() + '/api/v1/boxes/' + config.fqdn() + '/awscredentials';
     superagent.post(url).query({ token: apiConfig.token }).timeout(30 * 1000).end(function (error, result) {
         if (error && !error.response) return callback(error);
@@ -66,6 +71,11 @@ function getCaasCredentials(apiConfig, callback) {
 
         if (apiConfig.endpoint) credentials.endpoint = new AWS.Endpoint(apiConfig.endpoint);
 
+        gCachedCaasCredentials = {
+            issueDate: new Date(),
+            credentials: credentials
+        };
+
         callback(null, credentials);
     });
 }