AliceO2Group · ktf · Oct 2, 2019 · Sep 26, 2019
@@ -195,6 +195,32 @@ class CcdbApi //: public DatabaseInterface
  */
  void retrieveBlob(std::string const& path, std::string const& targetdir, std::map<std::string, std::string> const& metadata, long timestamp) const;

+  /**
+   * A helper function to extract an object from an existing in-memory TFile
+   * @param file a TFile instance
+   * @param objname name of serialized object
+   * @param cl The TClass object describing the serialized type
+   * @return raw pointer to created object
+   */
+  static void* extractFromTFile(TFile& file, std::string const& objname, TClass const* cl);
+
+  /** Get headers associated to a given CCDBEntry on the server. 
+   * @param url the url which refers to the objects
+   * @param etag of the previous reply
+   * @param headers the headers found in the request. Will be emptied when we return false.
+   * @return true if the headers where updated WRT last time, false if the previous results can still be used.
+   */
+  static bool getCCDBEntryHeaders(std::string const& url, std::string const& etag, std::vector<std::string>& headers);
+
+  /**
+   * Extract the possible locations for a file and check whether or not
+   * the current cached object is still valid.
+   * @param headers the headers to be parsed
+   * @param pfns the vector of pfns to be filled.
+   * @param etag the etag to be updated with the new value
+   */
+  static void parseCCDBHeaders(std::vector<std::string> const& headers, std::vector<std::string>& pfns, std::string& etag);
+
 private:
  /**
   * Initialize in local mode; Objects will be retrieved from snapshot
@@ -258,14 +284,6 @@ class CcdbApi //: public DatabaseInterface
   */
  void* extractFromLocalFile(std::string const& filename, std::string const& objname, TClass const* cl) const;

-  /**
-   * A helper function to extract an object from an existing in-memory TFile
-   * @param file a TFile instance
-   * @param objname name of serialized object
-   * @param cl The TClass object describing the serialized type
-   * @return raw pointer to created object
-   */
-  static void* extractFromTFile(TFile& file, std::string const& objname, TClass const* cl);

  /**
   * Initialization of CURL

@@ -824,6 +824,60 @@ std::vector<std::string> CcdbApi::parseSubFolders(std::string const& reply) cons
  return folders;
 }

+namespace
+{
+size_t header_callback(char* buffer, size_t size, size_t nitems, void* userdata)
+{
+  std::vector<std::string>* headers = static_cast<std::vector<std::string>*>(userdata);
+  auto header = std::string(buffer, size * nitems);
+  headers->emplace_back(std::string(header.data()));
+  return size * nitems;
+}
+} // namespace
+
+bool CcdbApi::getCCDBEntryHeaders(std::string const& url, std::string const& etag, std::vector<std::string>& headers)
+{
+  auto curl = curl_easy_init();
+  headers.clear();
+  if (!curl) {
+    return true;
+  }
+
+  struct curl_slist* list = nullptr;
+  list = curl_slist_append(list, ("If-None-Match: " + etag).c_str());
+
+  curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
+
+  curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
+  /* get us the resource without a body! */
+  curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);
+  curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
+  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);
+  curl_easy_setopt(curl, CURLOPT_HEADERDATA, &headers);
+
+  /* Perform the request */
+  curl_easy_perform(curl);
+  long http_code = 0;
+  curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
+  if (http_code == 304) {
+    return false;
+  }
+  return true;
+}
+
+void CcdbApi::parseCCDBHeaders(std::vector<std::string> const& headers, std::vector<std::string>& pfns, std::string& etag)
+{
+  static std::string etagHeader = "ETag: ";
+  static std::string locationHeader = "Content-Location: ";
+  for (auto h : headers) {
+    if (h.find(etagHeader) == 0) {
+      etag = std::string(h.data() + etagHeader.size());
+    } else if (h.find(locationHeader) == 0) {
+      pfns.emplace_back(std::string(h.data() + locationHeader.size(), h.size() - locationHeader.size()));
+    }
+  }
+}
+
 namespace
 {
 void traverseAndFillFolders(CcdbApi const& api, std::string const& top, std::vector<std::string>& folders)

@@ -368,3 +368,45 @@ BOOST_AUTO_TEST_CASE(list_test, *utf::precondition(if_reachable()))
  countItems(s, countObjects, countSubfolders);
  BOOST_CHECK_EQUAL(countObjects, 1);
 }
+
+BOOST_AUTO_TEST_CASE(TestHeaderParsing)
+{
+  std::vector<std::string> headers = {
+    "HTTP/1.1 200",
+    "Content-Location: /download/6dcb77c0-ca56-11e9-a807-200114580202",
+    "Date: Thu, 26 Sep 2019 08:09:20 GMT",
+    "Valid-Until: 1567771311999",
+    "Valid-From: 1567080816927",
+    "InitialValidityLimit: 1598616816927",
+    "Created: 1567080816956",
+    "ETag: \"6dcb77c0-ca56-11e9-a807-200114580202\"",
+    "Last-Modified: Thu, 29 Aug 2019 12:13:36 GMT",
+    "UpdatedFrom: 2001:1458:202:28:0:0:100:35",
+    "partName: send",
+    "Content-Disposition: inline;filename=\"o2::dataformats::CalibLHCphaseTOF_1567080816916.root\"",
+    "Accept-Ranges: bytes",
+    "Content-MD5: 9481c9d036660f80e21dae5943c2096f",
+    "Content-Type: application/octet-stream",
+    "Content-Length: 2097152"};
+  std::vector<std::string> results;
+  std::string etag;
+  CcdbApi::parseCCDBHeaders(headers, results, etag);
+  BOOST_CHECK_EQUAL(etag, "\"6dcb77c0-ca56-11e9-a807-200114580202\"");
+  BOOST_REQUIRE_EQUAL(results.size(), 1);
+  BOOST_CHECK_EQUAL(results[0], "/download/6dcb77c0-ca56-11e9-a807-200114580202");
+}
+
+BOOST_AUTO_TEST_CASE(TestFetchingHeaders, *utf::precondition(if_reachable()))
+{
+  std::string etag;
+  std::vector<std::string> headers;
+  std::vector<std::string> pfns;
+  auto updated = CcdbApi::getCCDBEntryHeaders("http://ccdb-test.cern.ch:8080/TOF/LHCphase/1567080816927", etag, headers);
+  BOOST_CHECK_EQUAL(updated, true);
+  BOOST_REQUIRE(headers.size() != 0);
+  CcdbApi::parseCCDBHeaders(headers, pfns, etag);
+  BOOST_REQUIRE(etag != "");
+  BOOST_REQUIRE(pfns.size());
+  updated = CcdbApi::getCCDBEntryHeaders("http://ccdb-test.cern.ch:8080/TOF/LHCphase/1567080816927", etag, headers);
+  BOOST_CHECK_EQUAL(updated, false);
+}