Extend Task with optional start time field.

Task start time will be updated when it's not set
or status update is ealier then current start time.

include/mesos/mesos.proto

@@ -1547,6 +1547,8 @@ message Task {
 
   // Specific user under which task is running.
   optional string user = 14;
+
+  optional double start_time = 15;
 }
 
 

src/common/http.cpp

@@ -360,6 +360,10 @@ JSON::Object model(const Task& task)
     object.values["container"] = JSON::protobuf(task.container());
   }
 
+  if (task.has_start_time()) {
+    object.values["start_time"] = task.start_time();
+  }
+
   return object;
 }
 

src/common/type_utils.cpp

@@ -392,7 +392,8 @@ bool operator==(const Task& left, const Task& right)
     left.status_update_uuid() == right.status_update_uuid() &&
     left.labels() == right.labels() &&
     left.discovery() == right.discovery() &&
-    left.user() == right.user();
+    left.user() == right.user() &&
+    left.start_time() == right.start_time();
 }
 
 

src/master/master.cpp

@@ -7822,6 +7822,12 @@ void Master::updateTask(Task* task, const StatusUpdate& update)
   // task transitioned to a new state.
   bool sendSubscribersUpdate = false;
 
+  // Set start_time
+  if (status.state() != TASK_STAGING &&
+          (!task->has_start_time() || status.timestamp() < task->start_time())) {
+    task->set_start_time(status.timestamp());
+  }
+
   // Set 'terminated' to true if this is the first time the task
   // transitioned to terminal state. Also set the latest state.
   bool terminated;

src/tests/common/http_tests.cpp

@@ -91,6 +91,7 @@ TEST(HTTPTest, ModelTask)
 
   Task task = createTask(taskInfo, state, frameworkId);
   task.add_statuses()->CopyFrom(statuses[0]);
+  task.set_start_time(1482932544);
 
   JSON::Value object = model(task);
 
@@ -140,7 +141,8 @@ TEST(HTTPTest, ModelTask)
       "   },"
       "   \"visibility\":\"CLUSTER\""
       " },"
-      " \"user\":\"user1\""
+      " \"user\":\"user1\","
+      " \"start_time\":1482932544"
       "}");
 
   ASSERT_SOME(expected);