Constructor
new Subscription(pubsub, name, optionsopt)
Parameters:
| Name | Type | Attributes | Description |
|---|---|---|---|
pubsub |
PubSub |
PubSub object. |
|
name |
string |
The name of the subscription. |
|
options |
SubscriberOptions |
<optional> |
Options for handling messages. |
Examples
From PubSub#getSubscriptions
```
const {PubSub} = require('@google-cloud/pubsub');
const pubsub = new PubSub();
pubsub.getSubscriptions((err, subscriptions) => {
// `subscriptions` is an array of Subscription objects.
});
```From Topic#getSubscriptions
```
const topic = pubsub.topic('my-topic');
topic.getSubscriptions((err, subscriptions) => {
// `subscriptions` is an array of Subscription objects.
});
```Topic#createSubscription
```
const topic = pubsub.topic('my-topic');
topic.createSubscription('new-subscription', (err, subscription) => {
// `subscription` is a Subscription object.
});
```Topic#subscription
```
const topic = pubsub.topic('my-topic');
const subscription = topic.subscription('my-subscription');
// `subscription` is a Subscription object.
```Once you have obtained a subscription object, you may begin to register listeners. This will automatically trigger pulling for messages.
```
// Register an error handler.
subscription.on('error', (err) => {});
// Register a debug handler, to catch non-fatal errors and other messages.
subscription.on('debug', msg => { console.log(msg.message); });
// Register a close handler in case the subscriber closes unexpectedly
subscription.on('close', () => {});
// Register a listener for `message` events.
function onMessage(message) {
// Called every time a message is received.
// message.id = ID of the message.
// message.ackId = ID used to acknowledge the message receival.
// message.data = Contents of the message.
// message.attributes = Attributes of the message.
// message.publishTime = Date when Pub/Sub received the message.
// Ack the message:
// message.ack();
// This doesn't ack the message, but allows more messages to be retrieved
// if your limit was hit or if you don't want to ack the message.
// message.nack();
}
subscription.on('message', onMessage);
// Remove the listener from receiving `message` events.
subscription.removeListener('message', onMessage);
```To apply a fine level of flow control, consider the following configuration
```
const subscription = topic.subscription('my-sub', {
flowControl: {
maxMessages: 1,
// this tells the client to manage and lock any excess messages
allowExcessMessages: false
}
});
```Members
iam
IAM (Identity and Access Management) allows you to set permissions on individual resources and offers a wider range of roles: editor, owner, publisher, subscriber, and viewer. This gives you greater flexibility and allows you to set more fine-grained access control.
The IAM access control features described in this document are Beta, including the API methods to get and set IAM policies, and to test IAM permissions. Cloud Pub/Sub's use of IAM features is not covered by any SLA or deprecation policy, and may be subject to backward-incompatible changes.
- Mixes In:
- See:
Example
```
//-
// Get the IAM policy for your subscription.
//-
subscription.iam.getPolicy((err, policy) => {
console.log(policy);
});
//-
// If the callback is omitted, we'll return a Promise.
//-
subscription.iam.getPolicy().then((data) => {
const policy = data[0];
const apiResponse = data[1];
});
```isOpen
Indicates if the Subscription is open and receiving messages.
projectId
Methods
open()
Opens the Subscription to receive messages. In general this method
shouldn't need to be called, unless you wish to receive messages after
calling Subscription#close. Alternatively one could just assign a
new message event listener which will also re-open the Subscription.
Example
```
subscription.on('message', message => message.ack());
// Close the subscription.
subscription.close(err => {
if (err) {
// Error handling omitted.
}
The subscription has been closed and messages will no longer be received.
});
// Resume receiving messages.
subscription.open();
```setOptions(options)
Sets the Subscription options.
Parameters:
| Name | Type | Description |
|---|---|---|
options |
SubscriberOptions |
The options. |
snapshot(name) → {Snapshot}
Create a Snapshot object. See Subscription#createSnapshot to create a snapshot.
Parameters:
| Name | Type | Description |
|---|---|---|
name |
string |
The name of the snapshot. |
Returns:
| Type | Description |
|---|---|
| Snapshot |
Throws:
-
If a name is not provided.
- Type
- Error