Backport PR jupyter#437: Avoid kernel failures with multiple processes

jupyter_client/client.py

@@ -51,7 +51,7 @@ class KernelClient(ConnectionFileMixin):
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context)
     def _context_default(self):
-        return zmq.Context.instance()
+        return zmq.Context()
 
     # The classes to use for the various channels
     shell_channel_class = Type(ChannelABC)

jupyter_client/tests/test_kernelmanager.py

@@ -11,6 +11,9 @@
 from subprocess import PIPE
 import sys
 import time
+import threading
+import multiprocessing as mp
+import pytest
 from unittest import TestCase
 
 from traitlets.config.loader import Config
@@ -28,7 +31,7 @@ def setUp(self):
 
     def tearDown(self):
         self.env_patch.stop()
-    
+
     def _install_test_kernel(self):
         kernel_dir = pjoin(paths.jupyter_data_dir(), 'kernels', 'signaltest')
         os.makedirs(kernel_dir)
@@ -127,3 +130,118 @@ def test_start_new_kernel(self):
 
         self.assertTrue(km.is_alive())
         self.assertTrue(kc.is_alive())
+
+@pytest.mark.parallel
+class TestParallel:
+
+    @pytest.fixture(autouse=True)
+    def env(self):
+        env_patch = test_env()
+        env_patch.start()
+        yield
+        env_patch.stop()
+
+    @pytest.fixture(params=['tcp', 'ipc'])
+    def transport(self, request):
+        return request.param
+
+    @pytest.fixture
+    def config(self, transport):
+        c = Config()
+        c.transport = transport
+        if transport == 'ipc':
+            c.ip = 'test'
+        return c
+
+    def _install_test_kernel(self):
+        kernel_dir = pjoin(paths.jupyter_data_dir(), 'kernels', 'signaltest')
+        os.makedirs(kernel_dir)
+        with open(pjoin(kernel_dir, 'kernel.json'), 'w') as f:
+            f.write(json.dumps({
+                'argv': [sys.executable,
+                         '-m', 'jupyter_client.tests.signalkernel',
+                         '-f', '{connection_file}'],
+                'display_name': "Signal Test Kernel",
+            }))
+
+    def test_start_sequence_kernels(self, config):
+        """Ensure that a sequence of kernel startups doesn't break anything."""
+
+        self._install_test_kernel()
+        self._run_signaltest_lifecycle(config)
+        self._run_signaltest_lifecycle(config)
+        self._run_signaltest_lifecycle(config)
+
+    def test_start_parallel_thread_kernels(self, config):
+        self._install_test_kernel()
+        self._run_signaltest_lifecycle(config)
+
+        thread = threading.Thread(target=self._run_signaltest_lifecycle, args=(config,))
+        thread2 = threading.Thread(target=self._run_signaltest_lifecycle, args=(config,))
+        try:
+            thread.start()
+            thread2.start()
+        finally:
+            thread.join()
+            thread2.join()
+
+    def test_start_parallel_process_kernels(self, config):
+        self._install_test_kernel()
+
+        self._run_signaltest_lifecycle(config)
+        thread = threading.Thread(target=self._run_signaltest_lifecycle, args=(config,))
+        proc = mp.Process(target=self._run_signaltest_lifecycle, args=(config,))
+        try:
+            thread.start()
+            proc.start()
+        finally:
+            thread.join()
+            proc.join()
+
+        assert proc.exitcode == 0
+
+    def test_start_sequence_process_kernels(self, config):
+        self._install_test_kernel()
+        self._run_signaltest_lifecycle(config)
+        proc = mp.Process(target=self._run_signaltest_lifecycle, args=(config,))
+        try:
+            proc.start()
+        finally:
+            proc.join()
+
+        assert proc.exitcode == 0
+
+    def _prepare_kernel(self, km, startup_timeout=TIMEOUT, **kwargs):
+        km.start_kernel(**kwargs)
+        kc = km.client()
+        kc.start_channels()
+        try:
+            kc.wait_for_ready(timeout=startup_timeout)
+        except RuntimeError:
+            kc.stop_channels()
+            km.shutdown_kernel()
+            raise
+
+        return kc
+
+    def _run_signaltest_lifecycle(self, config=None):
+        km = KernelManager(config=config, kernel_name='signaltest')
+        kc = self._prepare_kernel(km, stdout=PIPE, stderr=PIPE)
+
+        def execute(cmd):
+            kc.execute(cmd)
+            reply = kc.get_shell_msg(TIMEOUT)
+            content = reply['content']
+            assert content['status'] == 'ok'
+            return content
+
+        execute("start")
+        assert km.is_alive()
+        execute('check')
+        assert km.is_alive()
+
+        km.restart_kernel(now=True)
+        assert km.is_alive()
+        execute('check')
+
+        km.shutdown_kernel()