make ObjStore.GetObj wait until the object is present in the object store, other miscellaneous fixes

src/objstore.cc

@@ -1,4 +1,6 @@
 #include "objstore.h"
+#include <thread>
+#include <chrono>
 
 const size_t ObjStoreClient::CHUNK_SIZE = 8 * 1024;
 
@@ -84,13 +86,21 @@ Status ObjStoreService::GetObj(ServerContext* context, const GetObjRequest* requ
   // TODO(pcm): There is one remaining case where this can fail, i.e. if an object is
   // to be delivered from another store but hasn't yet arrived
   ObjRef objref = request->objref();
-  memory_lock_.lock();
+  while (true) {
+    // if the object has not been sent to the objstore, this has the potential to lead to an infinite loop
+    std::this_thread::sleep_for(std::chrono::milliseconds(10));
+    ORCH_LOG(ORCH_DEBUG, "looping in objstore " << objstoreid_ << " waiting for objref " << objref);
+    std::lock_guard<std::mutex> memory_lock(memory_lock_);
+    if (memory_.find(objref) != memory_.end()) {
+      break;
+    }
+  }
+  std::lock_guard<std::mutex> memory_lock(memory_lock_);
   shared_object& object = memory_[objref];
   reply->set_bucket(object.name);
   auto handle = object.memory->get_handle_from_address(object.ptr.data);
   reply->set_handle(handle);
   reply->set_size(object.ptr.len);
-  memory_lock_.unlock();
   return Status::OK;
 }
 

src/orchpylib.cc

@@ -393,7 +393,7 @@ PyObject* pull_object(PyObject* self, PyObject* args) {
   if (!PyArg_ParseTuple(args, "O&O&", &PyObjectToWorker, &worker, &PyObjectToObjRef, &objref)) {
     return NULL;
   }
-  slice s = worker->get_object(objref);
+  slice s = worker->pull_object(objref);
   Obj* obj = new Obj(); // TODO: Make sure this will get deleted
   obj->ParseFromString(std::string(s.data, s.len));
   return PyCapsule_New(static_cast<void*>(obj), "obj", NULL);

src/scheduler.cc

@@ -16,9 +16,9 @@ Status SchedulerService::RemoteCall(ServerContext* context, const RemoteCallRequ
     task->add_result(result);
   }
 
-  tasks_lock_.lock();
-  tasks_.emplace_back(std::move(task));
-  tasks_lock_.unlock();
+  task_queue_lock_.lock();
+  task_queue_.emplace_back(std::move(task));
+  task_queue_lock_.unlock();
 
   schedule();
   return Status::OK;
@@ -33,18 +33,25 @@ Status SchedulerService::PushObj(ServerContext* context, const PushObjRequest* r
 }
 
 Status SchedulerService::PullObj(ServerContext* context, const PullObjRequest* request, AckReply* reply) {
-  std::lock_guard<std::mutex> objtable_lock(objtable_lock_);
+  objtable_lock_.lock();
+  size_t size = objtable_.size();
+  objtable_lock_.unlock();
+
   ObjRef objref = request->objref();
-  if (objref >= objtable_.size() || objtable_[objref].size() == 0) {
+  if (objref >= size) {
     ORCH_LOG(ORCH_FATAL, "internal error: no object with objref " << objref << " exists");
   }
-  ObjStoreId objstoreid = pick_objstore(objref);
-  deliver_object(objref, objstoreid, get_store(request->workerid()));
+
+  pull_queue_lock_.lock();
+  pull_queue_.push_back(std::make_pair(request->workerid(), objref));
+  pull_queue_lock_.unlock();
+
+  schedule();
   return Status::OK;
 }
 
 Status SchedulerService::RegisterObjStore(ServerContext* context, const RegisterObjStoreRequest* request, RegisterObjStoreReply* reply) {
-  std::lock_guard<std::mutex> lock();
+  std::lock_guard<std::mutex> objstore_lock(objstores_lock_);
   ObjStoreId objstoreid = objstores_.size();
   auto channel = grpc::CreateChannel(request->address(), grpc::InsecureChannelCredentials());
   objstores_.push_back(ObjStoreHandle());
@@ -93,6 +100,9 @@ Status SchedulerService::SchedulerDebugInfo(ServerContext* context, const Schedu
 }
 
 void SchedulerService::deliver_object(ObjRef objref, ObjStoreId from, ObjStoreId to) {
+  if (from == to) {
+    ORCH_LOG(ORCH_FATAL, "attempting to deliver objref " << objref << " from objstore " << from << " to itself.");
+  }
   ClientContext context;
   AckReply reply;
   DeliverObjRequest request;
@@ -104,21 +114,49 @@ void SchedulerService::deliver_object(ObjRef objref, ObjStoreId from, ObjStoreId
 
 void SchedulerService::schedule() {
   // TODO: don't recheck if nothing changed
-  std::lock_guard<std::mutex> avail_workers_lock(avail_workers_lock_);
-  std::lock_guard<std::mutex> fntable_lock(fntable_lock_);
-  std::lock_guard<std::mutex> tasks_lock(tasks_lock_);
-  for (int i = 0; i < avail_workers_.size(); ++i) {
-    WorkerId workerid = avail_workers_[i];
-    for (auto it = tasks_.begin(); it != tasks_.end(); ++it) {
-      const Call& task = *(*it);
-      auto& workers = fntable_[task.name()].workers();
-      if (std::binary_search(workers.begin(), workers.end(), workerid) && can_run(task)) {
-        submit_task(std::move(*it), workerid);
-        tasks_.erase(it);
-        std::swap(avail_workers_[i], avail_workers_[avail_workers_.size() - 1]);
-        avail_workers_.pop_back();
+  {
+    std::lock_guard<std::mutex> objtable_lock(objtable_lock_);
+    std::lock_guard<std::mutex> pull_queue_lock(pull_queue_lock_);
+    // Complete all pull tasks that can be completed.
+    for (int i = 0; i < pull_queue_.size(); ++i) {
+      const std::pair<WorkerId, ObjRef>& pull = pull_queue_[i];
+      WorkerId workerid = pull.first;
+      ObjRef objref = pull.second;
+      if (objtable_[objref].size() > 0) {
+        if (!std::binary_search(objtable_[objref].begin(), objtable_[objref].end(), get_store(workerid))) {
+          // The worker's local object store does not already contain objref, so ship
+          // it there from an object store that does have it.
+          ObjStoreId objstoreid = pick_objstore(objref);
+          deliver_object(objref, objstoreid, get_store(workerid));
+        }
+        // Remove the pull task from the queue
+        std::swap(pull_queue_[i], pull_queue_[pull_queue_.size() - 1]);
+        pull_queue_.pop_back();
         i -= 1;
-        break;
+      }
+    }
+  }
+  {
+    std::lock_guard<std::mutex> fntable_lock(fntable_lock_);
+    std::lock_guard<std::mutex> avail_workers_lock(avail_workers_lock_);
+    std::lock_guard<std::mutex> task_queue_lock(task_queue_lock_);
+    for (int i = 0; i < avail_workers_.size(); ++i) {
+      // Submit all tasks whose arguments are ready.
+      WorkerId workerid = avail_workers_[i];
+      for (auto it = task_queue_.begin(); it != task_queue_.end(); ++it) {
+        // The use of erase(it) below invalidates the iterator, but we
+        // immediately break out of the inner loop, so the iterator is not used
+        // after the erase
+        const Call& task = *(*it);
+        auto& workers = fntable_[task.name()].workers();
+        if (std::binary_search(workers.begin(), workers.end(), workerid) && can_run(task)) {
+          submit_task(std::move(*it), workerid);
+          task_queue_.erase(it);
+          std::swap(avail_workers_[i], avail_workers_[avail_workers_.size() - 1]);
+          avail_workers_.pop_back();
+          i -= 1;
+          break;
+        }
       }
     }
   }
@@ -231,12 +269,12 @@ void SchedulerService::debug_info(const SchedulerDebugInfoRequest& request, Sche
     }
   }
   fntable_lock_.unlock();
-  tasks_lock_.lock();
-  for (const auto& entry : tasks_) {
+  task_queue_lock_.lock();
+  for (const auto& entry : task_queue_) {
     Call* call = reply->add_task();
     call->CopyFrom(*entry);
   }
-  tasks_lock_.unlock();
+  task_queue_lock_.unlock();
   avail_workers_lock_.lock();
   for (const WorkerId& entry : avail_workers_) {
     reply->add_avail_worker(entry);

src/scheduler.h

@@ -89,8 +89,11 @@ private:
   FnTable fntable_;
   std::mutex fntable_lock_;
   // List of pending tasks.
-  std::deque<std::unique_ptr<Call> > tasks_;
-  std::mutex tasks_lock_;
+  std::deque<std::unique_ptr<Call> > task_queue_;
+  std::mutex task_queue_lock_;
+  // List of pending pull calls.
+  std::vector<std::pair<WorkerId, ObjRef> > pull_queue_;
+  std::mutex pull_queue_lock_;
 };
 
 #endif

src/worker.cc

@@ -1,6 +1,9 @@
 # include "worker.h"
 
 Status WorkerServiceImpl::InvokeCall(ServerContext* context, const InvokeCallRequest* request, InvokeCallReply* reply) {
+  // TODO(rkn): This method opens a message_queue, which may consume a
+  // filehandle. This should be changed to only open a queue once in the
+  // constructor.
   call_ = request->call(); // Copy call
   ORCH_LOG(ORCH_INFO, "invoked task " << request->call().name());
   try {
@@ -13,10 +16,24 @@ Status WorkerServiceImpl::InvokeCall(ServerContext* context, const InvokeCallReq
     std::cout << ex.what() << std::endl;
     // TODO: return Status;
   }
-  message_queue::remove(worker_address_.c_str());
   return Status::OK;
 }
 
+Worker::Worker(const std::string& worker_address, std::shared_ptr<Channel> scheduler_channel, std::shared_ptr<Channel> objstore_channel)
+    : worker_address_(worker_address),
+      scheduler_stub_(Scheduler::NewStub(scheduler_channel)),
+      objstore_stub_(ObjStore::NewStub(objstore_channel)) {
+  try {
+    // This creates the receive message queue.
+    const char* message_queue_name = worker_address_.c_str();
+    message_queue::remove(message_queue_name);
+    receive_queue_ = std::unique_ptr<message_queue>(new message_queue(create_only, message_queue_name, 1, sizeof(Call*)));
+  }
+  catch(interprocess_exception &ex) {
+    std::cout << ex.what() << std::endl;
+  }
+}
+
 RemoteCallReply Worker::remote_call(RemoteCallRequest* request) {
   RemoteCallReply reply;
   ClientContext context;
@@ -108,18 +125,15 @@ void Worker::register_function(const std::string& name, size_t num_return_vals)
 Call* Worker::receive_next_task() {
   const char* message_queue_name = worker_address_.c_str();
   try {
-    message_queue::remove(message_queue_name);
-    message_queue mq(create_only, message_queue_name, 1, sizeof(Call*));
     unsigned int priority;
     message_queue::size_type recvd_size;
     Call* call;
     while (true) {
-      mq.receive(&call, sizeof(Call*), recvd_size, priority);
+      receive_queue_->receive(&call, sizeof(Call*), recvd_size, priority);
       return call;
     }
   }
   catch(interprocess_exception &ex){
-  	message_queue::remove(message_queue_name);
     std::cout << ex.what() << std::endl;
   }
 }

src/worker.h

@@ -37,11 +37,7 @@ private:
 
 class Worker {
  public:
-  Worker(const std::string& worker_address, std::shared_ptr<Channel> scheduler_channel, std::shared_ptr<Channel> objstore_channel)
-      : worker_address_(worker_address),
-        scheduler_stub_(Scheduler::NewStub(scheduler_channel)),
-        objstore_stub_(ObjStore::NewStub(objstore_channel))
-    {}
+  Worker(const std::string& worker_address, std::shared_ptr<Channel> scheduler_channel, std::shared_ptr<Channel> objstore_channel);
 
   // submit a remote call to the scheduler
   RemoteCallReply remote_call(RemoteCallRequest* request);
@@ -71,6 +67,7 @@ class Worker {
   std::unique_ptr<ObjStore::Stub> objstore_stub_;
   std::thread worker_server_thread_;
   std::thread other_thread_;
+  std::unique_ptr<message_queue> receive_queue_;
   managed_shared_memory segment_;
   WorkerId workerid_;
   std::string worker_address_;