[AIRFLOW-908] Print hostname at the start of cli run

Closes #2329 from AllisonWang/master

airflow/bin/cli.py

@@ -19,6 +19,7 @@ import logging
 import reprlib
 
 import os
+import socket
 import subprocess
 import textwrap
 import warnings
@@ -384,6 +385,9 @@ def run(args, dag=None):
             level=settings.LOGGING_LEVEL,
             format=settings.LOG_FORMAT)
 
+    hostname = socket.getfqdn()
+    logging.info("Running on host {}".format(hostname))
+
     if not args.pickle and not dag:
         dag = get_dag(args)
     elif not dag: