Fix support for sub-process (process pool)

trains/backend_interface/metrics/reporter.py

@@ -1,8 +1,8 @@
 import collections
 import json
 
-import cv2
 import six
+from threading import Thread, Event
 
 from ..base import InterfaceBase
 from ..setupuploadmixin import SetupUploadMixin
@@ -47,6 +47,13 @@ class Reporter(InterfaceBase, AbstractContextManager, SetupUploadMixin, AsyncMan
         self._bucket_config = None
         self._storage_uri = None
         self._async_enable = async_enable
+        self._flush_frequency = 30.0
+        self._exit_flag = False
+        self._flush_event = Event()
+        self._flush_event.clear()
+        self._thread = Thread(target=self._daemon)
+        self._thread.daemon = True
+        self._thread.start()
 
     def _set_storage_uri(self, value):
         value = '/'.join(x for x in (value.rstrip('/'), self._metrics.storage_key_prefix) if x)
@@ -70,10 +77,19 @@ class Reporter(InterfaceBase, AbstractContextManager, SetupUploadMixin, AsyncMan
     def async_enable(self, value):
         self._async_enable = bool(value)
 
+    def _daemon(self):
+        while not self._exit_flag:
+            self._flush_event.wait(self._flush_frequency)
+            self._flush_event.clear()
+            self._write()
+            # wait for all reports
+            if self.get_num_results() > 0:
+                self.wait_for_results()
+
     def _report(self, ev):
         self._events.append(ev)
         if len(self._events) >= self._flush_threshold:
-            self._write()
+            self.flush()
 
     def _write(self):
         if not self._events:
@@ -88,10 +104,12 @@ class Reporter(InterfaceBase, AbstractContextManager, SetupUploadMixin, AsyncMan
         """
         Flush cached reports to backend.
         """
-        self._write()
-        # wait for all reports
-        if self.get_num_results() > 0:
-            self.wait_for_results()
+        self._flush_event.set()
+
+    def stop(self):
+        self._exit_flag = True
+        self._flush_event.set()
+        self._thread.join()
 
     def report_scalar(self, title, series, value, iter):
         """