Implemented caching for sas response if a validity period is provided…

client/js/azure/get-sas.js

@@ -21,22 +21,44 @@ qq.azure.GetSas = function(o) {
 
  qq.extend(options, o);
 
- function sasResponseReceived(id, xhr, isError) {
- var promise = requestPromises[id];
+ function sasResponseReceived(params, xhr, isError) {
+ var promise = requestPromises[params.id];
 
  if (isError) {
  promise.failure("Received response code " + xhr.status, xhr);
  }
  else {
  if (xhr.responseText.length) {
- promise.success(xhr.responseText);
+
+ var responseJson;
+
+ try {
+ responseJson = JSON.parse(xhr.responseText);
+ } catch (error) {
+ options.log(qq.format("Validity period not provided for SAS for file ID {}. SAS request will be sent for each chunk. JSON parse error: '{}'", params.id, error));
+ }
+
+ if (responseJson) {
+ var sasData = {
+ sasUrl: responseJson.sasUrl,
+ validFor: responseJson.validFor - 15, // extract 15 seconds from validity time to cater for latency between client and server
+ requestedAtTimestamp: parseInt((new Date().getTime()) / 1000) // current timestamp (in seconds)
+ };
+
+ localStorage['qqazure_sas_' + params.blobUri] = JSON.stringify(sasData);
+
+ promise.success(sasData.sasUrl);
+ } else {
+ // fallback; only the sas is returned without expiration time
+ promise.success(xhr.responseText);
+ }
  }
  else {
  promise.failure("Empty response.", xhr);
  }
  }
 
- delete requestPromises[id];
+ delete requestPromises[params.id];
  }
 
  requester = qq.extend(this, new qq.AjaxRequester({
@@ -59,17 +81,36 @@ qq.azure.GetSas = function(o) {
  var requestPromise = new qq.Promise(),
  restVerb = options.restRequestVerb;
 
- options.log(qq.format("Submitting GET SAS request for a {} REST request related to file ID {}.", restVerb, id));
-
  requestPromises[id] = requestPromise;
 
- requester.initTransport(id)
- .withParams({
- bloburi: blobUri,
- _method: restVerb
- })
- .withCacheBuster()
- .send();
+ var cachedSasData = localStorage['qqazure_sas_' + blobUri];
+ var sasUrl;
+
+ if (cachedSasData) {
+ cachedSasData = JSON.parse(cachedSasData);
+ var currentTimestamp = parseInt((new Date().getTime()) / 1000);
+
+ // check if sas is valid based on timestamps
+ if (cachedSasData.validFor > (currentTimestamp - cachedSasData.requestedAtTimestamp)) {
+ sasUrl = cachedSasData.sasUrl;
+ }
+ }
+
+ if (sasUrl) {
+ options.log(qq.format("Ignoring GET SAS request for file ID {} because the previous request is still valid.", id)); 
+ requestPromise.success(sasUrl);
+ } else { 
+ options.log(qq.format("Submitting GET SAS request for a {} REST request related to file ID {}.", restVerb, id)); 
+ var params = { id: id, blobUri: blobUri };
+ requester.initTransport(params)
+ .withParams({
+ bloburi: blobUri,
+ _method: restVerb
+ })
+ .withCacheBuster()
+ .send();
+ }
+
 
  return requestPromise;
  }