[tune] Experiment Management API (#1328)

* init for exposing external interface

* revisions

* http server

* small

* simplify

* ui

* fixes

* test

* nit

* nit

* merge

* untested

* nits

* nit

* init tests

* tests

* more tests

* nit

* fix hyperband

* cleanup

* nits

* good stuff

* cleanup

* comments and need to test

* nit

* notebook

* testing

* test and expose server

* server_tests

* docs

* periods

* fix tests

* committing test

* fi

python/ray/tune/trial_scheduler.py

@@ -26,14 +26,24 @@ class TrialScheduler(object):
         """Called on each intermediate result returned by a trial.
 
         At this point, the trial scheduler can make a decision by returning
-        one of CONTINUE, PAUSE, and STOP."""
+        one of CONTINUE, PAUSE, and STOP. This will only be called when the
+        trial is in the RUNNING state."""
 
         raise NotImplementedError
 
     def on_trial_complete(self, trial_runner, trial, result):
         """Notification for the completion of trial.
 
-        This will only be called when the trial completes naturally."""
+        This will only be called when the trial is in the RUNNING state and
+        either completes naturally or by manual termination."""
+
+        raise NotImplementedError
+
+    def on_trial_remove(self, trial_runner, trial):
+        """Called to remove trial.
+
+        This is called when the trial is in PAUSED or PENDING state. Otherwise,
+        call `on_trial_complete`."""
 
         raise NotImplementedError
 
@@ -66,6 +76,9 @@ class FIFOScheduler(TrialScheduler):
     def on_trial_complete(self, trial_runner, trial, result):
         pass
 
+    def on_trial_remove(self, trial_runner, trial):
+        pass
+
     def choose_trial_to_run(self, trial_runner):
         for trial in trial_runner.get_trials():
             if (trial.status == Trial.PENDING and