[xray] Implement timeline and profiling API. (#2306)

* Add profile table and store profiling information there.

* Code for dumping timeline.

* Improve color scheme.

* Push timeline events on driver only for raylet.

* Improvements to profiling and timeline visualization

* Some linting

* Small fix.

* Linting

* Propagate node IP address through profiling events.

* Fix test.

* object_id.hex() should return byte string in python 2.

* Include gcs.fbs in node_manager.fbs.

* Remove flatbuffer definition duplication.

* Decode to unicode in Python 3 and bytes in Python 2.

* Minor

* Submit profile events in a batch. Revert some CMake changes.

* Fix

* Workaround test failure.

* Fix linting

* Linting

* Don't return anything from chrome_tracing_dump when filename is provided.

* Remove some redundancy from profile table.

* Linting

* Move TODOs out of docstring.

* Minor

python/ray/gcs_utils.py

@@ -22,6 +22,7 @@ import ray.core.generated.ErrorTableData
 from ray.core.generated.GcsTableEntry import GcsTableEntry
 from ray.core.generated.ClientTableData import ClientTableData
 from ray.core.generated.ErrorTableData import ErrorTableData
+from ray.core.generated.ProfileTableData import ProfileTableData
 from ray.core.generated.HeartbeatTableData import HeartbeatTableData
 from ray.core.generated.ObjectTableData import ObjectTableData
 from ray.core.generated.ray.protocol.Task import Task
@@ -33,9 +34,9 @@ __all__ = [
     "SubscribeToNotificationsReply", "ResultTableReply",
     "TaskExecutionDependencies", "TaskReply", "DriverTableMessage",
     "LocalSchedulerInfoMessage", "SubscribeToDBClientTableReply", "TaskInfo",
-    "GcsTableEntry", "ClientTableData", "ErrorTableData", "HeartbeatTableData",
-    "ObjectTableData", "Task", "TablePrefix", "TablePubsub",
-    "construct_error_message"
+    "GcsTableEntry", "ClientTableData", "ErrorTableData", "ProfileTableData",
+    "HeartbeatTableData", "ObjectTableData", "Task", "TablePrefix",
+    "TablePubsub", "construct_error_message"
 ]
 
 # These prefixes must be kept up-to-date with the definitions in
@@ -53,6 +54,7 @@ FUNCTION_PREFIX = "RemoteFunction:"
 TablePrefix_RAYLET_TASK_string = "RAYLET_TASK"
 TablePrefix_OBJECT_string = "OBJECT"
 TablePrefix_ERROR_INFO_string = "ERROR_INFO"
+TablePrefix_PROFILE_string = "PROFILE"
 
 
 def construct_error_message(error_type, message, timestamp):