ARANGODB_UPGRADE_DURING_RESTORE env variable. (#10385)

neunhoef · web-flow · commit b318ca8084fc · 2019-11-13T10:00:48.000+01:00
* ARANGODB_UPGRADE_DURING_RESTORE env variable.

If this is set during startup, a database upgrade is performed
and an automatic restart (with the same process ID) is happening.

* Windows compatibility.

* Deactivate code for Windows. Back to unsetenv.
diff --git a/arangod/RestServer/UpgradeFeature.cpp b/arangod/RestServer/UpgradeFeature.cpp
@@ -74,7 +74,36 @@ void UpgradeFeature::collectOptions(std::shared_ptr<ProgramOptions> options) {
                      arangodb::options::makeFlags(arangodb::options::Flags::Hidden));
 }
 
+/// @brief This external is buried in RestServer/arangod.cpp.
+///        Used to perform one last action upon shutdown.
+extern std::function<int()> * restartAction;
+
+#ifndef _WIN32
+static std::string const UPGRADE_ENV = "ARANGODB_UPGRADE_DURING_RESTORE";
+
+static int upgradeRestart() {
+  unsetenv(UPGRADE_ENV.c_str());
+  return 0;
+}
+#endif
+
 void UpgradeFeature::validateOptions(std::shared_ptr<ProgramOptions> options) {
+#ifndef _WIN32
+  // The following environment variable is another way to run a database
+  // upgrade. If the environment variable is set, the system does a database
+  // upgrade and then restarts itself without the environment variable.
+  // This is used in hotbackup if a restore to a backup happens which is from
+  // an older database version. The restore process sets the environment
+  // variable at runtime and then does a restore. After the restart (with
+  // the old data) the database upgrade is run and another restart is
+  // happening afterwards with the environment variable being cleared.
+  char* upgrade = getenv(UPGRADE_ENV.c_str());
+  if (upgrade != nullptr) {
+    _upgrade = true;
+    restartAction = new std::function<int()>();
+    *restartAction = upgradeRestart;
+  }
+#endif
   if (_upgrade && !_upgradeCheck) {
     LOG_TOPIC("47698", FATAL, arangodb::Logger::FIXME)
         << "cannot specify both '--database.auto-upgrade true' and "
