vpp_papi: Context_id allocator for running forked.

When running forked, distinct copies of the 'get_context'
singleton are created for each process.  To run under forked processes,
(as with make test TEST_JOBS=10), we need to use a shared
memory value across the processes.

Type: fix

Change-Id: I9eab8ce46ec23584e5bd651735ad75fd3f018e1a
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>

2 files changed, 60 insertions, 5 deletions

diff --git a/src/vpp-api/python/vpp_papi/tests/test_vpp_papi.py b/src/vpp-api/python/vpp_papi/tests/test_vpp_papi.py
new file mode 100644
index 00000000000..774b4e1092c
--- /dev/null
+++ b/src/vpp-api/python/vpp_papi/tests/test_vpp_papi.py
@@ -0,0 +1,53 @@
+#  Copyright (c) 2019. Vinci Consulting Corp. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+import ctypes
+import multiprocessing as mp
+import unittest
+from vpp_papi import vpp_papi
+
+
+class TestVppPapiVPPApiClient(unittest.TestCase):
+
+    def test_getcontext(self):
+        vpp_papi.VPPApiClient.apidir = '.'
+        c = vpp_papi.VPPApiClient(testmode=True, use_socket=True)
+
+        # reset initialization at module load time.
+        c.get_context.context = mp.Value(ctypes.c_uint, 0)
+        for _ in range(10):
+            c.get_context()
+        self.assertEqual(11, c.get_context())
+
+
+class TestVppPapiVPPApiClientMp(unittest.TestCase):
+    # Test under multiple processes to simulate running forked under
+    # run_tests.py (eg. make test TEST_JOBS=10)
+
+    def test_get_context_mp(self):
+        vpp_papi.VPPApiClient.apidir = '.'
+        c = vpp_papi.VPPApiClient(testmode=True, use_socket=True)
+
+        # reset initialization at module load time.
+        c.get_context.context = mp.Value(ctypes.c_uint, 0)
+        procs = [mp.Process(target=c.get_context, args=()) for i in range(10)]
+
+        for p in procs:
+            p.start()
+        for p in procs:
+            p.join()
+
+        # AssertionError: 11 != 1
+        self.assertEqual(11, c.get_context())
+
diff --git a/src/vpp-api/python/vpp_papi/vpp_papi.py b/src/vpp-api/python/vpp_papi/vpp_papi.py
index 8f179a21a9d..1f5cce23a79 100644
--- a/src/vpp-api/python/vpp_papi/vpp_papi.py
+++ b/src/vpp-api/python/vpp_papi/vpp_papi.py
@@ -16,7 +16,9 @@
 
 from __future__ import print_function
 from __future__ import absolute_import
+import ctypes
 import sys
+import multiprocessing as mp
 import os
 import logging
 import collections
@@ -263,16 +265,16 @@ class VPPApiClient(object):
         atexit.register(vpp_atexit, weakref.ref(self))
 
     class ContextId(object):
-        """Thread-safe provider of unique context IDs."""
+        """Multiprocessing-safe provider of unique context IDs."""
         def __init__(self):
-            self.context = 0
-            self.lock = threading.Lock()
+            self.context = mp.Value(ctypes.c_uint, 0)
+            self.lock = mp.Lock()
 
         def __call__(self):
             """Get a new unique (or, at least, not recently used) context."""
             with self.lock:
-                self.context += 1
-                return self.context
+                self.context.value += 1
+                return self.context.value
     get_context = ContextId()
 
     def get_type(self, name):