Adds token refresh to HTTP example. (GoogleCloudPlatform#517)

* Adds token refresh to HTTP example. * Review feedback

Author: gguuss

iot/http_example/README.md

@@ -34,6 +34,7 @@ Options:
   Either RS256 (RSA) or ES256 (Eliptic Curve)
  --cloud_region [region] GCP cloud region
  --num_messages [num] Number of messages to publish.
+ --token_exp_mins [num] Minutes to JWT token expiration.
  --http_bridge_address [address] HTTP bridge address.
  --message_type [events|state] The message type to publish.
 

iot/http_example/cloudiot_http_example_nodejs.js

@@ -66,6 +66,12 @@ var argv = require(`yargs`)
  requiresArg: true,
  type: 'number'
  },
+ token_exp_mins: {
+ default: 20,
+ description: 'Minutes to JWT token expiration.',
+ requiresArg: true,
+ type: 'number'
+ },
  http_bridge_address: {
  default: 'cloudiot-device.googleapis.com',
  description: 'HTTP bridge address.',
@@ -145,6 +151,14 @@ function publishAsync (messageCount, numMessages) {
  // If we have published fewer than numMessage messages, publish payload
  // messageCount + 1.
  setTimeout(function () {
+ let secsFromIssue = parseInt(Date.now() / 1000) - iatTime;
+ if (secsFromIssue > argv.token_exp_mins * 60) {
+ iatTime = parseInt(Date.now() / 1000);
+ console.log(`\tRefreshing token after ${secsFromIssue} seconds.`);
+
+ authToken = createJwt(argv.project_id, argv.private_key_file, argv.algorithm);
+ }
+
  publishAsync(messageCount + 1, numMessages);
  }, delayMs);
  }
@@ -161,7 +175,8 @@ const devicePath = `projects/${argv.project_id}/locations/${argv.cloud_region}/r
 const pathSuffix = argv.message_type === 'events'
  ? ':publishEvent' : ':setState';
 const url = `https://${argv.http_bridge_address}/v1beta1/${devicePath}${pathSuffix}`;
-const authToken = createJwt(argv.project_id, argv.private_key_file, argv.algorithm);
+let iatTime = parseInt(Date.now() / 1000);
+let authToken = createJwt(argv.project_id, argv.private_key_file, argv.algorithm);
 
 // Publish messages.
 publishAsync(1, argv.num_messages);