Region ID
The REGION_ID
is an abbreviated code that Google assigns
based on the region you select when you create your app. The code does not
correspond to a country or province, even though some region IDs may appear
similar to commonly used country and province codes. Including
REGION_ID.r
in App Engine URLs is optional for
existing apps and will soon be required for all new apps.
To ensure a smooth transition, we are slowly updating App Engine to use region IDs. If we haven't updated your Google Cloud project yet, you won't see a region ID for your app. Since the ID is optional for existing apps, you don't need to update URLs or make other changes once the region ID is available for your existing apps.
Learn more about region IDs.
Pub/Sub provides reliable, many-to-many, asynchronous messaging between applications. Publisher applications can send messages to a topic, and other applications can subscribe to that topic to receive the messages.
This document describes how to use the Cloud Client Library to send and receive Pub/Sub messages in a Node.js app.
Prerequisites
- Follow the instructions in "Hello, World!" for Node.js on App Engine to set up your environment and project, and to understand how App Engine Node.js apps are structured.
- Write down and save your project ID, because you will need it to run the sample application described in this document.
Cloning the sample app
Copy the sample apps to your local machine, and navigate to the pubsub
directory:
git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples
cd nodejs-docs-samples/appengine/pubsub
Creating a topic and subscription
Create a topic and subscription, which includes specifying the endpoint to which the Pub/Sub server should send requests:
gcloud pubsub topics create YOUR_TOPIC_NAME gcloud pubsub subscriptions create YOUR_SUBSCRIPTION_NAME \ --topic YOUR_TOPIC_NAME \ --push-endpoint \ https://YOUR_PROJECT_ID.REGION_ID.r.appspot.com/pubsub/push?token=YOUR_TOKEN \ --ack-deadline 10
Replace YOUR_TOKEN
with a secret random token. The push endpoint uses this
to verify requests.
Setting environment variables
Edit app.flexible.yaml
to set the environment variables for your project ID,
topic, and verification token:
Code review
The sample app uses the Cloud Client Libraries.
The sample app uses the values you set in the app.flexible.yaml
file to
configure environment variables. The push request handler uses these values to
confirm that the request came from Pub/Sub and originated from a trusted source:
// The following environment variables are set by app.flexible.yaml when
// running on App Engine, but will need to be manually set when running locally.
var PUBSUB_VERIFICATION_TOKEN = process.env.PUBSUB_VERIFICATION_TOKEN;
var pubsub = gcloud.pubsub({
projectId: process.env.GOOGLE_CLOUD_PROJECT
});
var topic = pubsub.topic(process.env.PUBSUB_TOPIC);
The sample app maintains a global list to store messages received by this instance:
// List of all messages received by this instance
var messages = [];
This method receives pushed messages and adds them to the messages
global list:
This method interacts with the App Engine web app to publish new messages and display received messages:
Running the sample locally
When running locally, you can use the Cloud SDK to provide authentication
to use Google Cloud APIs. Assuming you set up your environment as described in
Prerequisites, you have already run the gcloud init
command,
which provides this authentication.
Then set environment variables before starting your application:
export GOOGLE_CLOUD_PROJECT=[your-project-id]
export PUBSUB_VERIFICATION_TOKEN=[your-verification-token]
export PUBSUB_TOPIC=[your-topic]
npm install
npm start
Simulating push notifications
The application can send messages locally, but it is not able to receive push
messages locally. You can, however, simulate a push message by making an HTTP
request to the local push notification endpoint. The sample includes the file
sample_message.json
.
You can use curl
or
a httpie
client to
send an HTTP POST
request:
curl -H "Content-Type: application/json" -i --data @sample_message.json "localhost:8080/pubsub/push?token=[your-token]"
Or
http POST ":8080/pubsub/push?token=[your-token]" < sample_message.json
Response:
HTTP/1.1 200 OK
Connection: keep-alive
Date: Mon, 31 Aug 2015 22:19:50 GMT
Transfer-Encoding: chunked
X-Powered-By: Express
After the request completes, you can refresh localhost:8080
and see the
message in the list of received messages.
Running on App Engine
To deploy the demo app to App Engine by using the gcloud
command-line
tool, you run the following command from the directory where your
app.flexible.yaml
is located:
gcloud app deploy app.flexible.yaml
You can now access the application at
https://PROJECT_ID.REGION_ID.r.appspot.com
.
You can use the form to submit messages, but there's no guarantee of which
instance of your application will receive the notification. You can send
multiple messages and refresh the page to see the received message.