[tune] Better Serialization for Server (#3708)

* Add cloudpickle for serialization

* Fix tests

python/ray/tune/test/tune_server_test.py

@@ -6,6 +6,7 @@ import unittest
 import socket
 
 import ray
+from ray import tune
 from ray.rllib import _register_all
 from ray.tune.trial import Trial, Resources
 from ray.tune.web_server import TuneClient
@@ -87,6 +88,27 @@ class TuneServerSuite(unittest.TestCase):
         runner.step()
         self.assertEqual(len(all_trials), 2)
 
+    def testGetTrialsWithFunction(self):
+        runner, client = self.basicSetup()
+        test_trial = Trial(
+            "__fake",
+            trial_id="function_trial",
+            stopping_criterion={"training_iteration": 3},
+            config={
+                "callbacks": {
+                    "on_episode_start": tune.function(lambda x: None)
+                }
+            })
+        runner.add_trial(test_trial)
+
+        for i in range(3):
+            runner.step()
+        all_trials = client.get_all_trials()["trials"]
+        self.assertEqual(len(all_trials), 3)
+        client.get_trial("function_trial")
+        runner.step()
+        self.assertEqual(len(all_trials), 3)
+
     def testStopTrial(self):
         """Check if Stop Trial works."""
         runner, client = self.basicSetup()

python/ray/tune/web_server.py

@@ -7,8 +7,10 @@ import logging
 import sys
 import threading
 
+import ray.cloudpickle as cloudpickle
 from ray.tune.error import TuneError, TuneManagerError
 from ray.tune.suggest import BasicVariantGenerator
+from ray.utils import binary_to_hex, hex_to_binary
 
 if sys.version_info[0] == 2:
     from SimpleHTTPServer import SimpleHTTPRequestHandler
@@ -26,6 +28,13 @@ except ImportError:
                      "Be sure to install it on the client side.")
 
 
+def load_trial_info(trial_info):
+    trial_info["config"] = cloudpickle.loads(
+        hex_to_binary(trial_info["config"]))
+    trial_info["result"] = cloudpickle.loads(
+        hex_to_binary(trial_info["result"]))
+
+
 class TuneClient(object):
     """Client to interact with ongoing Tune experiment.
 
@@ -71,6 +80,13 @@ class TuneClient(object):
         payload = json.dumps(data).encode()
         response = requests.get(self._path, data=payload)
         parsed = response.json()
+
+        if "trial_info" in parsed:
+            load_trial_info(parsed["trial_info"])
+        elif "trials" in parsed:
+            for trial_info in parsed["trials"]:
+                load_trial_info(trial_info)
+
         return parsed
 
 
@@ -96,9 +112,9 @@ def RunnerHandler(runner):
             info_dict = {
                 "id": trial.trial_id,
                 "trainable_name": trial.trainable_name,
-                "config": trial.config,
+                "config": binary_to_hex(cloudpickle.dumps(trial.config)),
                 "status": trial.status,
-                "result": result
+                "result": binary_to_hex(cloudpickle.dumps(result))
             }
             return info_dict