Docker executor: better handling of the log produced inside the container

beat/core/execution/docker.py

@@ -417,9 +417,18 @@ class DockerExecutor(BaseExecutor):
 
 
         # Collects final information and returns to caller
+        container_log = self.host.stderr(algorithm_container)
+
+        stderr = ''
+        if status != 0:
+            stderr = container_log
+
+        if logger.getEffectiveLevel() <= logging.DEBUG:
+            logger.debug("Log of the container: " + container_log)
+
         retval = dict(
             stdout = self.host.stdout(algorithm_container),
-            stderr = self.host.stderr(algorithm_container),
+            stderr = stderr,
             status = status,
             timed_out = timed_out,
             statistics = self.host.statistics(algorithm_container),
@@ -434,7 +443,8 @@ class DockerExecutor(BaseExecutor):
 
         if databases_container is not None:
             retval['stdout'] += '\n' + self.host.stdout(databases_container)
-            retval['stderr'] += '\n' + self.host.stderr(databases_container)
+            if status != 0:
+                retval['stderr'] += '\n' + self.host.stderr(databases_container)
             self.host.rm(databases_container)
             self.db_socket.setsockopt(zmq.LINGER, 0)
             self.db_socket.close()