Changes to local scheduler client protocol. (#435)

* Make local scheduler clients receive reply upon registration.

* Fix tests and linting.

python/ray/global_scheduler/test/test.py

@@ -23,6 +23,7 @@
 ID_SIZE = 20
 NUM_CLUSTER_NODES = 2
 
+NIL_WORKER_ID = 20 * b"\xff"
 NIL_ACTOR_ID = 20 * b"\xff"
 
 # These constants must match the scheduling state enum in task.h.
@@ -101,7 +102,7 @@ def setUp(self):
           static_resource_list=[10, 0])
       # Connect to the scheduler.
       local_scheduler_client = local_scheduler.LocalSchedulerClient(
-          local_scheduler_name, NIL_ACTOR_ID, False)
+          local_scheduler_name, NIL_WORKER_ID, NIL_ACTOR_ID, False)
       self.local_scheduler_clients.append(local_scheduler_client)
       self.local_scheduler_pids.append(p4)
 

python/ray/local_scheduler/test/test.py

@@ -16,6 +16,7 @@
 USE_VALGRIND = False
 ID_SIZE = 20
 
+NIL_WORKER_ID = 20 * b"\xff"
 NIL_ACTOR_ID = 20 * b"\xff"
 
 
@@ -47,7 +48,7 @@ def setUp(self):
         plasma_store_name, use_valgrind=USE_VALGRIND)
     # Connect to the scheduler.
     self.local_scheduler_client = local_scheduler.LocalSchedulerClient(
-        scheduler_name, NIL_ACTOR_ID, False)
+        scheduler_name, NIL_WORKER_ID, NIL_ACTOR_ID, False)
 
   def tearDown(self):
     # Check that the processes are still alive.

python/ray/worker.py

@@ -1400,7 +1400,8 @@ def connect(info, object_id_seed=None, mode=WORKER_MODE, worker=global_worker,
                                                  info["manager_socket_name"])
   # Create the local scheduler client.
   worker.local_scheduler_client = ray.local_scheduler.LocalSchedulerClient(
-      info["local_scheduler_socket_name"], worker.actor_id, is_worker)
+      info["local_scheduler_socket_name"], worker.worker_id, worker.actor_id,
+      is_worker)
 
   # If this is a driver, set the current task ID, the task driver ID, and set
   # the task index to 0.

src/common/task.h

@@ -16,6 +16,7 @@ struct TaskBuilder;
 #define NIL_TASK_ID NIL_ID
 #define NIL_ACTOR_ID NIL_ID
 #define NIL_FUNCTION_ID NIL_ID
+#define NIL_WORKER_ID NIL_ID
 
 typedef UniqueID FunctionID;
 

src/local_scheduler/format/local_scheduler.fbs

@@ -10,10 +10,12 @@ enum MessageType:int {
   // Log a message to the event table. This is sent from a worker to a local
   // scheduler.
   EventLogMessage,
-  // Send an initial connection message to the local scheduler. This is ent from
-  // a worker to a local scheduler.
-  // This contains the worker's process ID and actor ID.
-  RegisterWorkerInfo,
+  // Send an initial connection message to the local scheduler. This is sent
+  // from a worker or driver to a local scheduler.
+  RegisterClientRequest,
+  // Send a reply confirming the successful registration of a worker or driver.
+  // This is sent from the local scheduler to a worker or driver.
+  RegisterClientReply,
   // Get a new task from the local scheduler. This is sent from a worker to a
   // local scheduler.
   GetTask,
@@ -31,21 +33,33 @@ enum MessageType:int {
   PutObject
 }
 
+// This message is sent from the local scheduler to a worker.
+table GetTaskReply {
+  // A string of bytes representing the task specification.
+  task_spec: string;
+}
+
 table EventLogMessage {
   key: string;
   value: string;
 }
 
 // This struct is used to register a new worker with the local scheduler.
 // It is shipped as part of local_scheduler_connect.
-table RegisterWorkerInfo {
-  // The ID of the actor.
-  // This is NIL_ACTOR_ID if the worker is not an actor.
+table RegisterClientRequest {
+  // True if the client is a worker and false if the client is a driver.
+  is_worker: bool;
+  // The ID of the worker or driver.
+  client_id: string;
+  // The ID of the actor. This is NIL_ACTOR_ID if the worker is not an actor.
   actor_id: string;
   // The process ID of this worker.
   worker_pid: long;
 }
 
+table RegisterClientReply {
+}
+
 table ReconstructObject {
   // Object ID of the object that needs to be reconstructed.
   object_id: string;

src/local_scheduler/local_scheduler.cc

@@ -458,8 +458,14 @@ void assign_task_to_worker(LocalSchedulerState *state,
                            TaskSpec *spec,
                            int64_t task_spec_size,
                            LocalSchedulerClient *worker) {
-  if (write_message(worker->sock, MessageType_ExecuteTask, task_spec_size,
-                    (uint8_t *) spec) < 0) {
+  /* Construct a flatbuffer object to send to the worker. */
+  flatbuffers::FlatBufferBuilder fbb;
+  auto message =
+      CreateGetTaskReply(fbb, fbb.CreateString((char *) spec, task_spec_size));
+  fbb.Finish(message);
+
+  if (write_message(worker->sock, MessageType_ExecuteTask, fbb.GetSize(),
+                    (uint8_t *) fbb.GetBufferPointer()) < 0) {
     if (errno == EPIPE || errno == EBADF) {
       /* TODO(rkn): If this happens, the task should be added back to the task
        * queue. */
@@ -646,6 +652,80 @@ void reconstruct_object(LocalSchedulerState *state,
                       reconstruct_object_lookup_callback, (void *) state);
 }
 
+void send_client_register_reply(LocalSchedulerState *state,
+                                LocalSchedulerClient *worker) {
+  flatbuffers::FlatBufferBuilder fbb;
+  auto message = CreateRegisterClientReply(fbb);
+  fbb.Finish(message);
+
+  /* Send the message to the client. */
+  if (write_message(worker->sock, MessageType_RegisterClientReply,
+                    fbb.GetSize(), fbb.GetBufferPointer()) < 0) {
+    if (errno == EPIPE || errno == EBADF || errno == ECONNRESET) {
+      /* Something went wrong, so kill the worker. */
+      kill_worker(worker, false);
+      LOG_WARN(
+          "Failed to give send register client reply to worker on fd %d. The "
+          "client may have hung up.",
+          worker->sock);
+    } else {
+      LOG_FATAL("Failed to send register client reply to client on fd %d.",
+                worker->sock);
+    }
+  }
+}
+
+void handle_client_register(LocalSchedulerState *state,
+                            LocalSchedulerClient *worker,
+                            const RegisterClientRequest *message) {
+  /* Register the worker or driver. */
+  if (message->is_worker()) {
+    /* Update the actor mapping with the actor ID of the worker (if an actor is
+     * running on the worker). */
+    int64_t worker_pid = message->worker_pid();
+    ActorID actor_id = from_flatbuf(message->actor_id());
+    if (!ActorID_equal(actor_id, NIL_ACTOR_ID)) {
+      /* Make sure that the local scheduler is aware that it is responsible for
+       * this actor. */
+      actor_map_entry *entry;
+      HASH_FIND(hh, state->actor_mapping, &actor_id, sizeof(actor_id), entry);
+      CHECK(entry != NULL);
+      CHECK(DBClientID_equal(entry->local_scheduler_id,
+                             get_db_client_id(state->db)));
+      /* Update the worker struct with this actor ID. */
+      CHECK(ActorID_equal(worker->actor_id, NIL_ACTOR_ID));
+      worker->actor_id = actor_id;
+      /* Let the scheduling algorithm process the presence of this new
+       * worker. */
+      handle_actor_worker_connect(state, state->algorithm_state, actor_id,
+                                  worker);
+    }
+
+    /* Register worker process id with the scheduler. */
+    worker->pid = worker_pid;
+    /* Determine if this worker is one of our child processes. */
+    LOG_DEBUG("PID is %d", worker_pid);
+    pid_t *child_pid;
+    int index = 0;
+    for (child_pid = (pid_t *) utarray_front(state->child_pids);
+         child_pid != NULL;
+         child_pid = (pid_t *) utarray_next(state->child_pids, child_pid)) {
+      if (*child_pid == worker_pid) {
+        /* If this worker is one of our child processes, mark it as a child so
+         * that we know that we can wait for the process to exit during
+         * cleanup. */
+        worker->is_child = true;
+        utarray_erase(state->child_pids, index, 1);
+        LOG_DEBUG("Found matching child pid %d", worker_pid);
+        break;
+      }
+      ++index;
+    }
+  } else {
+    /* Register the driver. Currently we don't do anything here. */
+  }
+}
+
 void process_message(event_loop *loop,
                      int client_sock,
                      void *context,
@@ -692,50 +772,11 @@ void process_message(event_loop *loop,
           (uint8_t *) message->value()->data(), message->value()->size());
     }
   } break;
-  case MessageType_RegisterWorkerInfo: {
-    /* Update the actor mapping with the actor ID of the worker (if an actor is
-     * running on the worker). */
-    auto message = flatbuffers::GetRoot<RegisterWorkerInfo>(
+  case MessageType_RegisterClientRequest: {
+    auto message = flatbuffers::GetRoot<RegisterClientRequest>(
         utarray_front(state->input_buffer));
-    int64_t worker_pid = message->worker_pid();
-    ActorID actor_id = from_flatbuf(message->actor_id());
-    if (!ActorID_equal(actor_id, NIL_ACTOR_ID)) {
-      /* Make sure that the local scheduler is aware that it is responsible for
-       * this actor. */
-      actor_map_entry *entry;
-      HASH_FIND(hh, state->actor_mapping, &actor_id, sizeof(actor_id), entry);
-      CHECK(entry != NULL);
-      CHECK(DBClientID_equal(entry->local_scheduler_id,
-                             get_db_client_id(state->db)));
-      /* Update the worker struct with this actor ID. */
-      CHECK(ActorID_equal(worker->actor_id, NIL_ACTOR_ID));
-      worker->actor_id = actor_id;
-      /* Let the scheduling algorithm process the presence of this new
-       * worker. */
-      handle_actor_worker_connect(state, state->algorithm_state, actor_id,
-                                  worker);
-    }
-
-    /* Register worker process id with the scheduler. */
-    worker->pid = worker_pid;
-    /* Determine if this worker is one of our child processes. */
-    LOG_DEBUG("PID is %d", worker_pid);
-    pid_t *child_pid;
-    int index = 0;
-    for (child_pid = (pid_t *) utarray_front(state->child_pids);
-         child_pid != NULL;
-         child_pid = (pid_t *) utarray_next(state->child_pids, child_pid)) {
-      if (*child_pid == worker_pid) {
-        /* If this worker is one of our child processes, mark it as a child so
-         * that we know that we can wait for the process to exit during
-         * cleanup. */
-        worker->is_child = true;
-        utarray_erase(state->child_pids, index, 1);
-        LOG_DEBUG("Found matching child pid %d", worker_pid);
-        break;
-      }
-      ++index;
-    }
+    handle_client_register(state, worker, message);
+    send_client_register_reply(state, worker);
   } break;
   case MessageType_GetTask: {
     /* If this worker reports a completed task: account for resources. */

src/local_scheduler/local_scheduler_client.cc

@@ -9,25 +9,40 @@
 
 LocalSchedulerConnection *LocalSchedulerConnection_init(
     const char *local_scheduler_socket,
+    UniqueID client_id,
     ActorID actor_id,
     bool is_worker) {
   LocalSchedulerConnection *result =
       (LocalSchedulerConnection *) malloc(sizeof(LocalSchedulerConnection));
   result->conn = connect_ipc_sock_retry(local_scheduler_socket, -1, -1);
 
-  if (is_worker) {
-    /* If we are a worker, register with the local scheduler.
-     * NOTE(swang): If the local scheduler exits and we are registered as a
-     * worker, we will get killed. */
-    flatbuffers::FlatBufferBuilder fbb;
-    auto message =
-        CreateRegisterWorkerInfo(fbb, to_flatbuf(fbb, actor_id), getpid());
-    fbb.Finish(message);
-    /* Register the process ID with the local scheduler. */
-    int success = write_message(result->conn, MessageType_RegisterWorkerInfo,
-                                fbb.GetSize(), fbb.GetBufferPointer());
-    CHECKM(success == 0, "Unable to register worker with local scheduler");
+  /* Register with the local scheduler.
+   * NOTE(swang): If the local scheduler exits and we are registered as a
+   * worker, we will get killed. */
+  flatbuffers::FlatBufferBuilder fbb;
+  auto message =
+      CreateRegisterClientRequest(fbb, is_worker, to_flatbuf(fbb, client_id),
+                                  to_flatbuf(fbb, actor_id), getpid());
+  fbb.Finish(message);
+  /* Register the process ID with the local scheduler. */
+  int success = write_message(result->conn, MessageType_RegisterClientRequest,
+                              fbb.GetSize(), fbb.GetBufferPointer());
+  CHECKM(success == 0, "Unable to register worker with local scheduler");
+
+  /* Wait for a confirmation from the local scheduler. */
+  int64_t type;
+  int64_t reply_size;
+  uint8_t *reply;
+  read_message(result->conn, &type, &reply_size, &reply);
+  if (type == DISCONNECT_CLIENT) {
+    LOG_WARN("Exiting because local scheduler closed connection.");
+    exit(1);
   }
+  CHECK(type == MessageType_RegisterClientReply);
+
+  /* Parse the reply object. We currently don't do anything with it. */
+  auto reply_message = flatbuffers::GetRoot<RegisterClientReply>(reply);
+  free(reply);
 
   return result;
 }
@@ -62,13 +77,27 @@ TaskSpec *local_scheduler_get_task(LocalSchedulerConnection *conn,
                                    int64_t *task_size) {
   write_message(conn->conn, MessageType_GetTask, 0, NULL);
   int64_t type;
+  int64_t message_size;
   uint8_t *message;
   /* Receive a task from the local scheduler. This will block until the local
    * scheduler gives this client a task. */
-  read_message(conn->conn, &type, task_size, &message);
+  read_message(conn->conn, &type, &message_size, &message);
+  if (type == DISCONNECT_CLIENT) {
+    LOG_WARN("Exiting because local scheduler closed connection.");
+    exit(1);
+  }
   CHECK(type == MessageType_ExecuteTask);
-  TaskSpec *task = (TaskSpec *) message;
-  return task;
+
+  /* Parse the flatbuffer object. */
+  auto reply_message = flatbuffers::GetRoot<GetTaskReply>(message);
+  /* Create a copy of the task spec so we can free the reply. */
+  *task_size = reply_message->task_spec()->size();
+  TaskSpec *spec = (TaskSpec *) malloc(*task_size);
+  memcpy(spec, reply_message->task_spec()->data(), *task_size);
+  /* Free the original message from the local scheduler. */
+  free(message);
+  /* Return the copy of the task spec and pass ownership to the caller. */
+  return spec;
 }
 
 void local_scheduler_task_done(LocalSchedulerConnection *conn) {

src/local_scheduler/local_scheduler_client.h

@@ -23,6 +23,7 @@ typedef struct {
  */
 LocalSchedulerConnection *LocalSchedulerConnection_init(
     const char *local_scheduler_socket,
+    UniqueID worker_id,
     ActorID actor_id,
     bool is_worker);
 

src/local_scheduler/local_scheduler_extension.cc

@@ -17,21 +17,25 @@ static int PyLocalSchedulerClient_init(PyLocalSchedulerClient *self,
                                        PyObject *args,
                                        PyObject *kwds) {
   char *socket_name;
+  UniqueID client_id;
   ActorID actor_id;
   PyObject *is_worker;
-  if (!PyArg_ParseTuple(args, "sO&O", &socket_name, PyStringToUniqueID,
-                        &actor_id, &is_worker)) {
+  self->local_scheduler_connection = NULL;
+  if (!PyArg_ParseTuple(args, "sO&O&O", &socket_name, PyStringToUniqueID,
+                        &client_id, PyStringToUniqueID, &actor_id,
+                        &is_worker)) {
     return -1;
   }
   /* Connect to the local scheduler. */
   self->local_scheduler_connection = LocalSchedulerConnection_init(
-      socket_name, actor_id, (bool) PyObject_IsTrue(is_worker));
+      socket_name, client_id, actor_id, (bool) PyObject_IsTrue(is_worker));
   return 0;
 }
 
 static void PyLocalSchedulerClient_dealloc(PyLocalSchedulerClient *self) {
-  LocalSchedulerConnection_free(
-      ((PyLocalSchedulerClient *) self)->local_scheduler_connection);
+  if (self->local_scheduler_connection != NULL) {
+    LocalSchedulerConnection_free(self->local_scheduler_connection);
+  }
   Py_TYPE(self)->tp_free((PyObject *) self);
 }