Understanding Subscriptions per Connection Limit in AWS AppSync
AWS AppSync is a powerful service that allows developers to build scalable and secure GraphQL APIs. One of the key features of AppSync is the ability to use WebSockets to establish long-lived connections between clients and the API. This enables real-time data updates and push notifications. However, it's important to understand that there is a limit to the number of subscriptions that can be active on a single WebSocket connection.
Subscriptions per Connection Limit
The subscriptions per connection limit in AWS AppSync refers to the number of subscription code statements that can be active on a single WebSocket connection. This limit is in place to ensure that the connection is not overloaded and that the API remains responsive. The current limit is 100 subscriptions per connection.
Key Concepts
To understand the subscriptions per connection limit, it's important to first understand some key concepts:
- GraphQL: A query language for APIs that allows clients to request specific data and shapes from the server.
- WebSocket: A protocol for establishing long-lived, two-way connections between clients and servers.
- Subscription: A GraphQL operation that allows clients to request real-time updates for a specific piece of data.
Applications
The subscriptions per connection limit is important to consider when building real-time applications with AWS AppSync. Some examples of applications that may be affected by this limit include:
- Chat applications, where multiple users may be subscribed to the same channel or room
- Collaborative editing tools, where multiple users may be editing the same document in real-time
- Real-time analytics dashboards, where multiple data points may be updated in real-time
Significance
Understanding the subscriptions per connection limit is important for ensuring that your application is performant and scalable. Exceeding this limit can result in slower data updates and increased latency. It's important to design your application in such a way that the number of active subscriptions per connection is kept below the limit. This may involve splitting up subscriptions across multiple connections, or using a different method for real-time updates, such as server-sent events.
Code Example
Here is an example of how to create a subscription in AWS AppSync using the AWS Amplify library:
import { API, graphqlOperation } from 'aws-amplify';
import { onCreateMessage } from './graphql/subscriptions';
const subscription = API.graphql(
graphqlOperation(onCreateMessage)
).subscribe({
next: (data) => {
console.log(data);
},
error: (error) => {
console.log(error);
}
});
In summary, the subscriptions per connection limit in AWS AppSync is an important consideration for building real-time applications. By understanding this limit and designing your application accordingly, you can ensure that your application is performant and scalable. Some key takeaways:
- The subscriptions per connection limit is 100 subscriptions per connection
- Exceeding this limit can result in slower data updates and increased latency
- Design your application to keep the number of active subscriptions per connection below the limit