Check if port is occupied before starting Kolibri

kolibri/utils/cli.py

@@ -24,6 +24,7 @@
 
 from . import server  # noqa
 from .system import become_daemon  # noqa
+from .sanity_checks import check_other_kolibri_running  # noqa
 
 USAGE = """
 Kolibri
@@ -262,12 +263,9 @@ def start(port=None, daemon=True):
     # https://github.com/learningequality/kolibri/issues/1615
     update()
 
-    if port is None:
-        try:
-            port = int(os.environ['KOLIBRI_LISTEN_PORT'])
-        except ValueError:
-            logger.error("Invalid KOLIBRI_LISTEN_PORT, must be an integer")
-            raise
+    # In case that some tests run start() function only
+    if not isinstance(port, int):
+        port = _get_port(port)
 
     if not daemon:
         logger.info("Running 'kolibri start' in foreground...")
@@ -314,6 +312,7 @@ def stop():
         pid, __, __ = server.get_status()
         server.stop(pid=pid)
         stopped = True
+        logger.info("Kolibri server has successfully been stoppped.")
     except server.NotRunning as e:
         verbose_status = "{msg:s} ({code:d})".format(
             code=e.status_code,
@@ -576,6 +575,17 @@ def parse_args(args=None):
     return docopt(USAGE, **docopt_kwargs), django_args
 
 
+def _get_port(port):
+    port = int(port) if port else None
+    if port is None:
+        try:
+            port = int(os.environ['KOLIBRI_LISTEN_PORT'])
+        except ValueError:
+            logger.error("Invalid KOLIBRI_LISTEN_PORT, must be an integer")
+            raise
+    return port
+
+
 def main(args=None):
     """
     Kolibri's main function. Parses arguments and calls utility functions.
@@ -589,6 +599,10 @@ def main(args=None):
 
     debug = arguments['--debug']
 
+    if arguments['start']:
+        port = _get_port(arguments['--port'])
+        check_other_kolibri_running(port)
+
     initialize(debug=debug)
 
     # Alias
@@ -607,8 +621,6 @@ def main(args=None):
         return
 
     if arguments['start']:
-        port = arguments['--port']
-        port = int(port) if port else None
         daemon = not arguments['--foreground']
         if sys.platform == 'darwin':
             daemon = False

kolibri/utils/sanity_checks.py

@@ -0,0 +1,44 @@
+import logging
+import socket
+import sys
+
+from .server import get_status
+from .server import NotRunning
+
+logger = logging.getLogger(__name__)
+
+def check_other_kolibri_running(port):
+    try:
+        # Check if there are other kolibri instances running
+        # If there are, then we need to stop users from starting kolibri again.
+        pid, listen_address, listen_port = get_status()
+        logger.error(
+            "There is another Kolibri server running. "
+            "Please use `kolibri stop` and try again."
+        )
+        sys.exit(1)
+
+    except NotRunning:
+        # In case that something other than Kolibri occupies the port,
+        # check the port's availability.
+        check_port_availability('127.0.0.1', port)
+
+
+def check_port_availability(host, port):
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    # This is to prevent the previous execution has left the socket
+    # in a TIME_WAIT start, and can't be immediately reused.
+    # From the bottom of https://docs.python.org/2/library/socket.html#example
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    try:
+        s.bind((host, port))
+        s.close()
+    except socket.error:
+        # Port is occupied
+        logger.error(
+            "Port {} is occupied.\n"
+            "Please check that you do not have other processes "
+            "running on this port and try again.\n".format(port)
+        )
+        s.close()
+        sys.exit(1)