Added drain example

Signed-off-by: Waldemar Quevedo <[email protected]>

examples/drain-example.py

@@ -0,0 +1,68 @@
+# coding: utf-8
+# Copyright 2015-2018 The NATS Authors
+# 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 tornado.gen
+import tornado.concurrent
+
+from nats.io import Client as NATS
+from nats.io.errors import ErrNoServers
+from tornado.ioloop import IOLoop as loop
+
+@tornado.gen.coroutine
+def main():
+    nc = NATS()
+
+    conn_closed = tornado.concurrent.Future()
+
+    def closed_cb():
+        conn_closed.set_result(True)
+
+    # Set pool servers in the cluster and give a name to the client.
+    yield nc.connect("127.0.0.1:4222", closed_cb=closed_cb)
+
+    @tornado.gen.coroutine
+    def handler(msg):
+        # Can check whether client is in draining state
+        if nc.is_draining:
+            print("[Status  ] Draining, will disconnect soon...")
+
+        print("[Received] {}".format(msg.data))
+        yield nc.publish(msg.reply, b'I can help')
+
+    yield nc.subscribe("help", "workers", cb=handler)
+
+    responses = []
+
+    @tornado.gen.coroutine
+    def send_requests():
+        # Send 100 async requests and wait for all the responses.
+        for i in range(0, 1000):
+            try:
+                response = yield nc.request("help", '[{}] help!'.format(i), timeout=0.1)
+                responses.append(response)
+            except:
+                break
+
+    loop.current().spawn_callback(send_requests)
+    yield tornado.gen.sleep(1)
+
+    # Gracefully close the connection and wait for closed callback to be signaled.
+    yield nc.drain()
+    yield conn_closed
+
+    print("Received {} responses".format(len(responses)))
+
+if __name__ == '__main__':
+    loop.current().run_sync(main)