In this lesson, we will explore real-time communication in GraphQL using subscriptions. GraphQL subscriptions enable clients to receive live updates from the server whenever specific events occur. This feature is particularly useful in applications where data changes frequently, and clients need to stay up-to-date with the latest information.
What is a Subscription?
A subscription is a GraphQL operation that enables clients to receive real-time updates when specific events occur on the server. Subscriptions are similar to queries and mutations, but they use the WebSocket protocol to maintain a persistent connection between the client and the server. This connection allows the server to push updates to the client when specific events occur, such as creating or deleting data, which can help create a more interactive and engaging user experience.
How do Subscriptions work internally?
Subscriptions work by maintaining a persistent connection between the client and server, usually using the WebSocket protocol. When a client subscribes to an event, it sends a subscription request to the server. The server then adds the client's subscription to an internal list and listens for the specified events.
When an event occurs, the server processes the event, resolves the subscription's payload, and pushes the data to all subscribed clients over the WebSocket connection. This process ensures that clients receive real-time updates for events they have subscribed to.
