Added dedicated startup phase

arangod/Pregel/Conductor.cpp

@@ -168,7 +168,7 @@ void Conductor::start() {
 
     auto body = std::make_shared<std::string const>(b.toJson());
     requests.emplace_back("server:" + it.first, rest::RequestType::POST,
-                          baseUrl + Utils::nextGSSPath, body);
+                          baseUrl + Utils::startExecutionPath, body);
   }
   size_t nrDone = 0;
   cc->performRequests(requests, 120.0, nrDone, LogTopic("Pregel Conductor"));
@@ -176,6 +176,34 @@ void Conductor::start() {
             << _vertexCollections[0]->name();
   // look at results
   printResults(requests);
+  
+  if (nrDone == requests.size()) {
+    startGlobalStep();
+  } else {
+    LOG(ERR) << "Not all DBServers started the execution";
+  }
+}
+
+void Conductor::startGlobalStep() {
+  
+  VPackBuilder b;
+  b.openObject();
+  b.add(Utils::executionNumberKey, VPackValue(_executionNumber));
+  b.add(Utils::globalSuperstepKey, VPackValue(_globalSuperstep));
+  b.add(Utils::aggregatorValuesKey, VPackValue(VPackValueType::Object));
+  for (std::unique_ptr<Aggregator>& aggregator : _aggregators) {
+    aggregator->serializeValue(b);
+  }
+  b.close();
+  b.close();
+  
+  std::string baseUrl = Utils::baseUrl(_vocbaseGuard.vocbase()->name());
+  sendToAllDBServers(baseUrl + Utils::startGSSPath, b.slice());
+  
+  for (std::unique_ptr<Aggregator>& aggregator : _aggregators) {
+    aggregator->reset();
+  }
+  LOG(INFO) << "Conductor started new gss " << _globalSuperstep;
 }
 
 void Conductor::finishedGlobalStep(VPackSlice& data) {
@@ -207,8 +235,8 @@ void Conductor::finishedGlobalStep(VPackSlice& data) {
     LOG(INFO) << "Finished gss " << _globalSuperstep;
     _globalSuperstep++;
 
-    std::string baseUrl = Utils::baseUrl(_vocbaseGuard.vocbase()->name());
     if (_doneCount == _dbServerCount || _globalSuperstep == 101) {
+      std::string baseUrl = Utils::baseUrl(_vocbaseGuard.vocbase()->name());
       LOG(INFO) << "Done. We did " << _globalSuperstep - 1 << " rounds";
       VPackBuilder b;
       b.openObject();
@@ -217,24 +245,8 @@ void Conductor::finishedGlobalStep(VPackSlice& data) {
       b.close();
       sendToAllDBServers(baseUrl + Utils::finalizeExecutionPath, b.slice());
       _state = ExecutionState::FINISHED;
-
     } else {  // trigger next superstep
-      VPackBuilder b;
-      b.openObject();
-      b.add(Utils::executionNumberKey, VPackValue(_executionNumber));
-      b.add(Utils::globalSuperstepKey, VPackValue(_globalSuperstep));
-      b.add(Utils::aggregatorValuesKey, VPackValue(VPackValueType::Object));
-      for (std::unique_ptr<Aggregator>& aggregator : _aggregators) {
-        aggregator->serializeValue(b);
-      }
-      b.close();
-      b.close();
-      sendToAllDBServers(baseUrl + Utils::nextGSSPath, b.slice());
-
-      for (std::unique_ptr<Aggregator>& aggregator : _aggregators) {
-        aggregator->reset();
-      }
-      LOG(INFO) << "Conductor started new gss " << _globalSuperstep;
+      startGlobalStep();
     }
   }
 }
@@ -248,7 +260,7 @@ int Conductor::sendToAllDBServers(std::string path, VPackSlice const& config) {
   _doneCount = 0;
 
   if (_dbServerCount == 0) {
-    LOG(WARN) << "No shards registered for " << _vertexCollections[0]->name();
+    LOG(WARN) << "No servers registered";
     return TRI_ERROR_FAILED;
   }
 
@@ -261,8 +273,7 @@ int Conductor::sendToAllDBServers(std::string path, VPackSlice const& config) {
 
   size_t nrDone = 0;
   cc->performRequests(requests, 120.0, nrDone, LogTopic("Pregel Conductor"));
-  LOG(INFO) << "Send messages to " << nrDone << " shards of "
-            << _vertexCollections[0]->name();
+  LOG(INFO) << "Send messages to " << nrDone << " servers";
   printResults(requests);
 
   return TRI_ERROR_NO_ERROR;

arangod/Pregel/Conductor.h

@@ -53,10 +53,10 @@ class Conductor {
 
  private:
   Mutex _finishedGSSMutex;  // prevents concurrent calls to finishedGlobalStep
+  
   VocbaseGuard _vocbaseGuard;
   const unsigned int _executionNumber;
   std::string _algorithm;
-
   ExecutionState _state = ExecutionState::RUNNING;
 
   std::vector<std::unique_ptr<Aggregator>> _aggregators;
@@ -69,7 +69,7 @@ class Conductor {
   int32_t _responseCount = 0;
   int32_t _doneCount = 0;
 
-  // convenience method
+  void startGlobalStep();
   int sendToAllDBServers(std::string url, VPackSlice const& body);
 };
 }

arangod/Pregel/OutgoingCache.cpp

@@ -134,7 +134,7 @@ void OutgoingCache<V, E, M>::sendMessageTo(std::string const& toValue,
 
 template <typename V, typename E, typename M>
 void OutgoingCache<V, E, M>::sendMessages() {
-  LOG(INFO) << "Beggining to send messages to other machines";
+  LOG(INFO) << "Beginning to send messages to other machines";
 
   std::vector<ClusterCommRequest> requests;
   for (auto const& it : _map) {

arangod/Pregel/PregelFeature.cpp

@@ -23,13 +23,13 @@
 #include "PregelFeature.h"
 #include "Conductor.h"
 #include "Worker.h"
+#include "Cluster/ClusterInfo.h"
 
 using namespace arangodb::pregel;
 
 static PregelFeature* Instance;
 
-static unsigned int _exeI = 0;
-unsigned int PregelFeature::createExecutionNumber() { return ++_exeI; }
+unsigned int PregelFeature::createExecutionNumber() { return ClusterInfo::instance()->uniqid(); }
 
 PregelFeature::PregelFeature(application_features::ApplicationServer* server)
     : ApplicationFeature(server, "Pregel") {

arangod/Pregel/Utils.cpp

@@ -33,7 +33,8 @@ using namespace arangodb::pregel;
 
 std::string const Utils::apiPrefix = "/_api/pregel/";
 
-std::string const Utils::nextGSSPath = "nextGSS";
+std::string const Utils::startExecutionPath = "startExecution";
+std::string const Utils::startGSSPath = "startGSS";
 std::string const Utils::finishedGSSPath = "finishedGSS";
 std::string const Utils::messagesPath = "messages";
 std::string const Utils::finalizeExecutionPath = "finalizeExecution";

arangod/Pregel/Utils.h

@@ -38,7 +38,8 @@ class Utils {
   // constants
   static std::string const apiPrefix;
 
-  static std::string const nextGSSPath;
+  static std::string const startExecutionPath;
+  static std::string const startGSSPath;
   static std::string const finishedGSSPath;
   static std::string const messagesPath;
   static std::string const finalizeExecutionPath;

arangod/Pregel/Worker.cpp

@@ -100,7 +100,7 @@ Worker<V, E, M>::~Worker() {
 
 /// @brief Setup next superstep
 template <typename V, typename E, typename M>
-void Worker<V, E, M>::nextGlobalStep(VPackSlice data) {
+void Worker<V, E, M>::startGlobalStep(VPackSlice data) {
   LOG(INFO) << "Called next global step: " << data.toJson();
 
   // TODO do some work?
@@ -121,10 +121,12 @@ void Worker<V, E, M>::nextGlobalStep(VPackSlice data) {
 
   // parse aggregated values
   VPackSlice aggregatedValues = data.get(Utils::aggregatorValuesKey);
-  for (auto const& pair : _aggregators) {
-    VPackSlice val = aggregatedValues.get(pair.second->name());
-    if (!val.isNone()) {
-      pair.second->setAggregatedValue(val);
+  if (aggregatedValues.isObject()) {
+    for (auto const& pair : _aggregators) {
+      VPackSlice val = aggregatedValues.get(pair.second->name());
+      if (!val.isNone()) {
+        pair.second->setAggregatedValue(val);
+      }
     }
   }
 

arangod/Pregel/Worker.h

@@ -34,7 +34,7 @@ namespace pregel {
 class IWorker {
  public:
   virtual ~IWorker(){};
-  virtual void nextGlobalStep(VPackSlice data) = 0;  // called by coordinator
+  virtual void startGlobalStep(VPackSlice data) = 0;  // called by coordinator
   virtual void receivedMessages(VPackSlice data) = 0;
   virtual void finalizeExecution(VPackSlice data) = 0;
 
@@ -51,7 +51,7 @@ class Worker : public IWorker {
          std::shared_ptr<WorkerState<V, E, M>> context);
   ~Worker();
 
-  void nextGlobalStep(VPackSlice data) override;  // called by coordinator
+  void startGlobalStep(VPackSlice data) override;  // called by coordinator
   void receivedMessages(VPackSlice data) override;
   void finalizeExecution(VPackSlice data) override;
 

arangod/RestHandler/RestPregelHandler.cpp

@@ -68,6 +68,27 @@ RestStatus RestPregelHandler::execute() {
         generateError(rest::ResponseCode::NOT_FOUND,
                       TRI_ERROR_HTTP_NOT_FOUND);
         return RestStatus::DONE;
+      } else if (suffix[0] == Utils::startExecutionPath) {
+        IWorker *w = PregelFeature::instance()->worker(executionNumber);
+        if (w) {
+          LOG(ERR) << "Worker with this execution number already exists.";
+          generateError(rest::ResponseCode::BAD,
+                        TRI_ERROR_HTTP_FORBIDDEN);
+          return RestStatus::DONE;
+        }
+        LOG(INFO) << "creating worker";
+        w = IWorker::createWorker(_vocbase, body);
+        PregelFeature::instance()->addWorker(w, executionNumber);
+      } else if (suffix[0] == Utils::startGSSPath) {
+        IWorker *w = PregelFeature::instance()->worker(executionNumber);
+        if (w) {
+          w->startGlobalStep(body);
+        } else {
+          LOG(ERR) << "Invalid execution number, worker does not exist.";
+          generateError(rest::ResponseCode::NOT_FOUND,
+                        TRI_ERROR_HTTP_NOT_FOUND);
+          return RestStatus::DONE;
+        }
       } else if (suffix[0] == Utils::finishedGSSPath) {
         Conductor *exe = PregelFeature::instance()->conductor(executionNumber);
         if (exe) {
@@ -75,14 +96,6 @@ RestStatus RestPregelHandler::execute() {
         } else {
           LOG(ERR) << "Conductor not found: " << executionNumber;
         }
-      } else if (suffix[0] == Utils::nextGSSPath) {
-        IWorker *w = PregelFeature::instance()->worker(executionNumber);
-        if (!w) {// can happen if gss == 0
-          LOG(INFO) << "creating worker";
-          w = IWorker::createWorker(_vocbase, body);
-          PregelFeature::instance()->addWorker(w, executionNumber);
-        }
-        w->nextGlobalStep(body);
       } else if (suffix[0] == Utils::messagesPath) {
         LOG(INFO) << "messages";
         IWorker *exe = PregelFeature::instance()->worker(executionNumber);