Adds token refresh to MQTT example. (GoogleCloudPlatform#1197)

* Adds token refresh to MQTT example.

* Fixes lint error.

iot/api-client/mqtt_example/README.rst

@@ -0,0 +1,107 @@
+.. This file is automatically generated. Do not edit this file directly.
+
+Google Cloud IoT Core API Python Samples
+===============================================================================
+
+This directory contains samples for Google Cloud IoT Core API. `Google Cloud IoT Core`_ allows developers to easily integrate Publish and Subscribe functionality with devices and programmatically manage device authorization.
+The following example runs the sample using the project ID `blue-jet-123` and the device name `my-python-device`:
+
+    python cloudiot_mqtt_example.py \
+        --registry_id=my-registry \
+        --project_id=blue-jet-123 \
+        --device_id=my-python-device \
+        --algorithm=RS256 \
+        --private_key_file=../rsa_private.pem
+
+
+
+
+.. _Google Cloud IoT Core API: https://cloud.google.com/iot/docs 
+
+Setup
+-------------------------------------------------------------------------------
+
+
+Install Dependencies
+++++++++++++++++++++
+
+#. Install `pip`_ and `virtualenv`_ if you do not already have them. You may want to refer to the `Python Development Environment Setup Guide`_ for Google Cloud Platform for instructions.
+
+ .. _Python Development Environment Setup Guide:
+     https://cloud.google.com/python/setup
+
+#. Create a virtualenv. Samples are compatible with Python 2.7 and 3.4+.
+
+    .. code-block:: bash
+
+        $ virtualenv env
+        $ source env/bin/activate
+
+#. Install the dependencies needed to run the samples.
+
+    .. code-block:: bash
+
+        $ pip install -r requirements.txt
+
+.. _pip: https://pip.pypa.io/
+.. _virtualenv: https://virtualenv.pypa.io/
+
+Samples
+-------------------------------------------------------------------------------
+
+MQTT Device Client Example
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+
+
+To run this sample:
+
+.. code-block:: bash
+
+    $ python cloudiot_mqtt_example.py
+
+    usage: cloudiot_mqtt_example.py [-h] [--project_id PROJECT_ID] --registry_id
+                                    REGISTRY_ID --device_id DEVICE_ID
+                                    --private_key_file PRIVATE_KEY_FILE
+                                    --algorithm {RS256,ES256}
+                                    [--cloud_region CLOUD_REGION]
+                                    [--ca_certs CA_CERTS]
+                                    [--num_messages NUM_MESSAGES]
+                                    [--message_type {event,state}]
+                                    [--mqtt_bridge_hostname MQTT_BRIDGE_HOSTNAME]
+                                    [--mqtt_bridge_port {8883,443}]
+                                    [--jwt_expires_minutes JWT_EXPIRES_MINUTES]
+    
+    Example Google Cloud IoT Core MQTT device connection code.
+    
+    optional arguments:
+      -h, --help            show this help message and exit
+      --project_id PROJECT_ID
+                            GCP cloud project name
+      --registry_id REGISTRY_ID
+                            Cloud IoT Core registry id
+      --device_id DEVICE_ID
+                            Cloud IoT Core device id
+      --private_key_file PRIVATE_KEY_FILE
+                            Path to private key file.
+      --algorithm {RS256,ES256}
+                            Which encryption algorithm to use to generate the JWT.
+      --cloud_region CLOUD_REGION
+                            GCP cloud region
+      --ca_certs CA_CERTS   CA root from https://pki.google.com/roots.pem
+      --num_messages NUM_MESSAGES
+                            Number of messages to publish.
+      --message_type {event,state}
+                            Indicates whether the message to be published is a
+                            telemetry event or a device state message.
+      --mqtt_bridge_hostname MQTT_BRIDGE_HOSTNAME
+                            MQTT bridge hostname.
+      --mqtt_bridge_port {8883,443}
+                            MQTT bridge port.
+      --jwt_expires_minutes JWT_EXPIRES_MINUTES
+                            Expiration time, in minutes, for JWT tokens.
+
+
+
+
+.. _Google Cloud SDK: https://cloud.google.com/sdk/

iot/api-client/mqtt_example/README.rst.in

@@ -0,0 +1,30 @@
+# This file is used to generate README.rst
+
+product:
+  name: Google Cloud IoT Core API
+  short_name: Cloud IoT Core
+  url: https://cloud.google.com/iot/docs
+  description: >
+    `Google Cloud IoT Core`_ allows developers to easily integrate Publish and
+    Subscribe functionality with devices and programmatically manage device
+    authorization.
+
+    The following example runs the sample using the project ID `blue-jet-123`
+    and the device name `my-python-device`:
+
+        python cloudiot_mqtt_example.py \
+            --registry_id=my-registry \
+            --project_id=blue-jet-123 \
+            --device_id=my-python-device \
+            --algorithm=RS256 \
+            --private_key_file=../rsa_private.pem
+
+setup:
+- install_deps
+
+samples:
+- name: MQTT Device Client Example
+  file: cloudiot_mqtt_example.py
+  show_help: True
+
+cloud_client_library: false

iot/api-client/mqtt_example/cloudiot_mqtt_example.py

@@ -29,6 +29,7 @@
 import jwt
 import paho.mqtt.client as mqtt
 
+
 # [START iot_mqtt_jwt]
 def create_jwt(project_id, private_key_file, algorithm):
     """Creates a JWT (https://jwt.io) to establish an MQTT connection.
@@ -64,6 +65,8 @@ def create_jwt(project_id, private_key_file, algorithm):
     return jwt.encode(token, private_key, algorithm=algorithm)
 # [END iot_mqtt_jwt]
 
+
+# [START iot_mqtt_config]
 def error_str(rc):
     """Convert a Paho error to a human readable string."""
     return '{}: {}'.format(rc, mqtt.error_string(rc))
@@ -84,6 +87,46 @@ def on_publish(unused_client, unused_userdata, unused_mid):
     print('on_publish')
 
 
+def get_client(
+        project_id, cloud_region, registry_id, device_id, private_key_file,
+        algorithm, ca_certs, mqtt_bridge_hostname, mqtt_bridge_port):
+    """Create our MQTT client. The client_id is a unique string that identifies
+    this device. For Google Cloud IoT Core, it must be in the format below."""
+    client = mqtt.Client(
+            client_id=('projects/{}/locations/{}/registries/{}/devices/{}'
+                       .format(
+                               project_id,
+                               cloud_region,
+                               registry_id,
+                               device_id)))
+
+    # With Google Cloud IoT Core, the username field is ignored, and the
+    # password field is used to transmit a JWT to authorize the device.
+    client.username_pw_set(
+            username='unused',
+            password=create_jwt(
+                    project_id, private_key_file, algorithm))
+
+    # Enable SSL/TLS support.
+    client.tls_set(ca_certs=ca_certs)
+
+    # Register message callbacks. https://eclipse.org/paho/clients/python/docs/
+    # describes additional callbacks that Paho supports. In this example, the
+    # callbacks just print to standard out.
+    client.on_connect = on_connect
+    client.on_publish = on_publish
+    client.on_disconnect = on_disconnect
+
+    # Connect to the Google MQTT bridge.
+    client.connect(mqtt_bridge_hostname, mqtt_bridge_port)
+
+    # Start the network loop.
+    client.loop_start()
+
+    return client
+# [END iot_mqtt_config]
+
+
 def parse_command_line_args():
     """Parse command line arguments."""
     parser = argparse.ArgumentParser(description=(
@@ -131,57 +174,48 @@ def parse_command_line_args():
             default=8883,
             type=int,
             help='MQTT bridge port.')
+    parser.add_argument(
+            '--jwt_expires_minutes',
+            default=20,
+            type=int,
+            help=('Expiration time, in minutes, for JWT tokens.'))
 
     return parser.parse_args()
 
 
+# [START iot_mqtt_run]
 def main():
     args = parse_command_line_args()
 
-    # Create our MQTT client. The client_id is a unique string that identifies
-    # this device. For Google Cloud IoT Core, it must be in the format below.
-    client = mqtt.Client(
-            client_id=('projects/{}/locations/{}/registries/{}/devices/{}'
-                       .format(
-                               args.project_id,
-                               args.cloud_region,
-                               args.registry_id,
-                               args.device_id)))
-
-    # With Google Cloud IoT Core, the username field is ignored, and the
-    # password field is used to transmit a JWT to authorize the device.
-    client.username_pw_set(
-            username='unused',
-            password=create_jwt(
-                    args.project_id, args.private_key_file, args.algorithm))
-
-    # Enable SSL/TLS support.
-    client.tls_set(ca_certs=args.ca_certs)
-
-    # Register message callbacks. https://eclipse.org/paho/clients/python/docs/
-    # describes additional callbacks that Paho supports. In this example, the
-    # callbacks just print to standard out.
-    client.on_connect = on_connect
-    client.on_publish = on_publish
-    client.on_disconnect = on_disconnect
-
-    # Connect to the Google MQTT bridge.
-    client.connect(args.mqtt_bridge_hostname, args.mqtt_bridge_port)
-
-    # Start the network loop.
-    client.loop_start()
-
     # Publish to the events or state topic based on the flag.
     sub_topic = 'events' if args.message_type == 'event' else 'state'
 
     mqtt_topic = '/devices/{}/{}'.format(args.device_id, sub_topic)
 
+    jwt_iat = datetime.datetime.utcnow()
+    jwt_exp_mins = args.jwt_expires_minutes
+    client = get_client(
+        args.project_id, args.cloud_region, args.registry_id, args.device_id,
+        args.private_key_file, args.algorithm, args.ca_certs,
+        args.mqtt_bridge_hostname, args.mqtt_bridge_port)
+
     # Publish num_messages mesages to the MQTT bridge once per second.
     for i in range(1, args.num_messages + 1):
         payload = '{}/{}-payload-{}'.format(
                 args.registry_id, args.device_id, i)
         print('Publishing message {}/{}: \'{}\''.format(
                 i, args.num_messages, payload))
+        seconds_since_issue = (datetime.datetime.utcnow() - jwt_iat).seconds
+        if seconds_since_issue > 60 * jwt_exp_mins:
+            print('Refreshing token after {}s').format(seconds_since_issue)
+            client.loop_stop()
+            jwt_iat = datetime.datetime.utcnow()
+            client = get_client(
+                args.project_id, args.cloud_region,
+                args.registry_id, args.device_id, args.private_key_file,
+                args.algorithm, args.ca_certs, args.mqtt_bridge_hostname,
+                args.mqtt_bridge_port)
+
         # Publish "payload" to the MQTT topic. qos=1 means at least once
         # delivery. Cloud IoT Core also supports qos=0 for at most once
         # delivery.
@@ -193,6 +227,7 @@ def main():
     # End the network loop and finish.
     client.loop_stop()
     print('Finished.')
+# [END iot_mqtt_run]
 
 
 if __name__ == '__main__':