Catch all exceptions to prevent maintenance workers from crashing. (#6645)

* Catch all exceptions to prevent maintenance workers from crashing.
* Please don't free this.
* Unified code paths.
* Remove dub comment.
* Removed debug output.
* Deleted unneeded constructors.
* Assignment operator deleted.

arangod/Agency/Supervision.cpp

@@ -974,8 +974,6 @@ void Supervision::cleanupLostCollections(Node const& snapshot, AgentInterface *a
 
   auto const& trx = builder->slice();
 
-  LOG_TOPIC(ERR, Logger::FIXME) << "Trx: " << trx.toJson();
-
   if(trx.length() > 0) {
     // do it! fire and forget!
     agent->write(builder);

arangod/Cluster/Action.h

@@ -51,6 +51,11 @@ public:
   /// @brief construct with description
   Action(MaintenanceFeature&, std::shared_ptr<ActionDescription> const&);
 
+  Action(Action const&) = delete;
+  Action(Action &&) = delete;
+  Action() = delete;
+  Action& operator=(Action const&) = delete;
+
   /**
    * @brief construct with concrete action base
    * @param feature  Maintenance feature

arangod/Cluster/MaintenanceWorker.cpp

@@ -57,6 +57,7 @@ void MaintenanceWorker::run() {
 
   while(eSTOP != _loopState && !_feature.isShuttingDown()){
 
+    try {
       switch(_loopState) {
         case eFIND_ACTION:
           _curAction = _feature.findReadyAction(_labels);
@@ -79,9 +80,36 @@ void MaintenanceWorker::run() {
 
       } // switch
 
+    } catch(std::exception const& ex) {
+      if (_curAction) {
+        LOG_TOPIC(ERR, Logger::CLUSTER)
+          << "MaintenanceWorkerRun:  caught exception (" << ex.what() << ")"
+          << " state:" << _loopState
+          << " action:" << *_curAction;
+
+        _curAction->setState(FAILED);
+      } else {
+        LOG_TOPIC(ERR, Logger::CLUSTER)
+          << "MaintenanceWorkerRun:  caught exception (" << ex.what() << ")"
+          << " state:" << _loopState;
+      }
+    } catch(...) {
+      if (_curAction) {
+        LOG_TOPIC(ERR, Logger::CLUSTER)
+          << "MaintenanceWorkerRun: caught error, state: " << _loopState
+          << " state:" << _loopState
+          << " action:" << *_curAction;
+
+        _curAction->setState(FAILED);
+      } else {
+        LOG_TOPIC(ERR, Logger::CLUSTER)
+          << "MaintenanceWorkerRun: caught error, state: " << _loopState
+          << " state:" << _loopState;
+      }
+    }
+
     // determine next loop state
     nextState(more);
-
   } // while
 
 } // MaintenanceWorker::run
@@ -145,7 +173,6 @@ void MaintenanceWorker::nextState(bool actionMore) {
         } // else
       } else {
         std::shared_ptr<Action> failAction(_curAction);
-
         // fail all actions that would follow
         do {
           failAction->setState(FAILED);