Unsubscribing in GraphQL

Introduction

Unsubscribing stops receiving updates or messages you no longer want. It helps keep your data and notifications clean and relevant.

You no longer want to get live updates about a chat or news feed.

You want to stop receiving notifications from a specific topic or event.

You want to save resources by stopping unnecessary data flow.

You want to clean up your active subscriptions to avoid confusion.

You want to control what information your app listens to.

Syntax

GraphQL

subscription MySubscription {
  newMessages {
    id
    content
  }
}

// To unsubscribe, call the unsubscribe method on the subscription object returned by the client.

GraphQL subscriptions are usually started via a client method that returns a subscription object.

To stop receiving updates, you call unsubscribe() on that subscription object.

Examples

This example shows starting a subscription and then stopping it by calling unsubscribe().

GraphQL

// Start subscription
const subscription = client.subscribe({ query: MY_SUBSCRIPTION }).subscribe({});

// Later, to unsubscribe
subscription.unsubscribe();

Unsubscribing stops the flow of new comment data.

GraphQL

const subscription = client.subscribe({ query: NEW_COMMENTS }).subscribe({});

// Stop receiving new comments
subscription.unsubscribe();

Sample Program

This code starts a GraphQL subscription to listen for new messages. It prints each new message received. After 5 seconds, it stops the subscription to stop receiving updates.

GraphQL

const { ApolloClient, InMemoryCache, gql } = require('@apollo/client/core');
const { WebSocketLink } = require('@apollo/client/link/ws');
const ws = require('ws');

const link = new WebSocketLink({
  uri: 'ws://localhost:4000/graphql',
  options: { reconnect: true },
  webSocketImpl: ws
});

const client = new ApolloClient({
  link,
  cache: new InMemoryCache()
});

const NEW_MESSAGES = gql`
  subscription {
    newMessages {
      id
      content
    }
  }
`;

const subscription = client.subscribe({ query: NEW_MESSAGES }).subscribe({
  next(data) {
    console.log('New message:', data.data.newMessages);
  },
  error(err) {
    console.error('Subscription error:', err);
  }
});

// Unsubscribe after 5 seconds
setTimeout(() => {
  subscription.unsubscribe();
  console.log('Unsubscribed from newMessages');
}, 5000);

Important Notes

Always unsubscribe when you no longer need updates to save bandwidth and resources.

Failing to unsubscribe can cause memory leaks or unwanted data processing.

Summary

Unsubscribing stops live updates from a GraphQL subscription.

Call unsubscribe() on the subscription object to stop.

This keeps your app efficient and avoids unwanted data.

Practice

1.

What does calling unsubscribe() on a GraphQL subscription do?

easy

A. It pauses the subscription but keeps the connection alive.

B. It restarts the subscription to receive updates again.

C. It deletes the subscription from the server permanently.

D. It stops receiving live updates from the subscription.

Solution

1. Step 1: Understand the purpose of unsubscribe()

   The unsubscribe() method is designed to stop live updates from a GraphQL subscription.

2. Step 2: Differentiate from other actions

   It does not restart, delete permanently, or pause the subscription; it simply stops updates.

3. Final Answer:

   It stops receiving live updates from the subscription. -> Option D

4. Quick Check:

   Unsubscribe() stops updates = D [OK]

Hint: Remember: unsubscribe() means stop updates completely [OK]

Common Mistakes:

• Thinking unsubscribe() restarts the subscription
• Confusing unsubscribe() with deleting the subscription
• Assuming unsubscribe() only pauses updates

2.

Which of the following is the correct syntax to stop a GraphQL subscription stored in variable sub?

const sub = client.subscribe({ query: MY_SUBSCRIPTION });
// Stop subscription here

easy

A. sub.stop();

B. unsubscribe(sub);

C. sub.unsubscribe();

D. client.unsubscribe(sub);

Solution

1. Step 1: Identify the unsubscribe method on subscription object

   The subscription object returned by client.subscribe() has an unsubscribe() method to stop it.

2. Step 2: Match correct syntax

   Calling sub.unsubscribe(); correctly stops the subscription. Other options are invalid method calls.

3. Final Answer:

   sub.unsubscribe(); -> Option C

4. Quick Check:

   Call unsubscribe() on subscription object = A [OK]

Hint: Use unsubscribe() method on the subscription variable [OK]

Common Mistakes:

• Using unsubscribe() as a standalone function
• Calling stop() instead of unsubscribe()
• Trying to unsubscribe via client object

3.

Given the code below, what will be logged after sub.unsubscribe() is called?

const sub = client.subscribe({ query: MY_SUBSCRIPTION });
sub.subscribe({
  next(data) { console.log('Received:', data); },
  error(err) { console.error('Error:', err); }
});

sub.unsubscribe();

// Later, server sends new data

medium

A. An error will be logged because subscription is closed.

B. No logs will appear after unsubscribe is called.

C. Logs will continue showing 'Received:' with new data.

D. Logs will show 'Received:' once more then stop.

Solution

1. Step 1: Understand unsubscribe effect on subscription callbacks

   Calling unsubscribe() stops the subscription and prevents further next callbacks.

2. Step 2: Predict logging behavior after unsubscribe

   Since subscription is stopped, no new data triggers console.log, so no logs appear after unsubscribe.

3. Final Answer:

   No logs will appear after unsubscribe is called. -> Option B

4. Quick Check:

   Unsubscribe stops callbacks = C [OK]

Hint: After unsubscribe, no more data callbacks occur [OK]

Common Mistakes:

• Expecting data logs after unsubscribe
• Assuming unsubscribe triggers an error
• Thinking one last data event logs after unsubscribe

4.

Identify the error in the code below that prevents unsubscribing correctly:

const subscription = client.subscribe({ query: NEW_MESSAGES });
subscription.next({
  next(data) { console.log(data); }
});

subscription.unsubscribe();

medium

A. Using subscription.next() instead of subscription.subscribe().

B. Calling unsubscribe() before subscribing.

C. Missing error callback in subscription.

D. Not assigning subscription to a variable.

Solution

1. Step 1: Check subscription method usage

   The subscription object uses subscribe() to listen for data, not next().

2. Step 2: Identify correct method to receive data

   Replacing subscription.next() with subscription.subscribe() fixes the issue and allows unsubscribe to work properly.

3. Final Answer:

   Using subscription.next() instead of subscription.subscribe(). -> Option A

4. Quick Check:

   Use subscribe(), not next(), to listen = B [OK]

Hint: Use subscribe() method to listen, not next() [OK]

Common Mistakes:

• Calling next() instead of subscribe()
• Unsubscribing before subscribing
• Ignoring error callback (not critical here)

5.

You have multiple active subscriptions stored in an array subs. How do you efficiently unsubscribe from all of them?

const subs = [sub1, sub2, sub3];
// Your code here

hard

A. subs.forEach(s => s.unsubscribe());

B. subs.unsubscribe();

C. for (let i = 0; i < subs.length; i++) { unsubscribe(subs[i]); }

D. subs.map(s => s.stop());

Solution

1. Step 1: Understand unsubscribing multiple subscriptions

   Each subscription object has an unsubscribe() method to stop it individually.

2. Step 2: Use array iteration to call unsubscribe on each

   Using subs.forEach(s => s.unsubscribe()); calls unsubscribe on all subscriptions efficiently.

3. Final Answer:

   subs.forEach(s => s.unsubscribe()); -> Option A

4. Quick Check:

   Call unsubscribe() on each subscription in array = A [OK]

Hint: Use forEach to unsubscribe all in array [OK]

Common Mistakes:

• Calling unsubscribe() on the array itself
• Using stop() method which does not exist
• Trying to call unsubscribe() without iteration