How to Broadcast Server-Side Events in gRPC with Long-Polling?

Broadcasting Server-Side Events in gRPC

When building a chat application with gRPC, the need often arises for server-to-client broadcasting. The challenge lies in the server being able to identify connected clients and broadcast events to all of them simultaneously.

One approach to achieve this is through the use of an observer pattern. However, the server is unaware of who is connected and how to broadcast to specific clients.

An alternative solution is the application of server-side streaming. While each client possesses its own stream, it is impractical to subscribe to multiple streams.

Long-Polling Implementation for Broadcasting

A viable option for broadcasting events in gRPC is to implement a long-polling approach:

1. Protobuf Definitions: Define a protobuf interface for the "Updater" service, allowing clients to retrieve updates and the server to broadcast them.
2. Server Implementation: Implement a server that includes a condition variable to signal updates. When an update occurs, it notifies all waiting clients.
3. Client Implementation: Create a separate thread in each client that continuously polls the server for updates. When updates become available, the thread handles them and updates the request to retrieve the next set of updates.

This approach ensures that all clients receive updates as they occur, providing a reliable and scalable broadcast mechanism for server-side events in gRPC.

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