For More Stable Repl Connections

Replit manages Session Success Rate as its core SLO (Service Level Objective), prioritizing the stable connection of client requests to the target Repl.

Previously, Conman, the container manager, simultaneously handled container execution and the reverse WebSocket proxy role. This caused a problem where updating Conman would shut down both the proxy and the containers at the same time, disconnecting users, and resource sharing also made it difficult to implement Autoscaling based on container count.

To solve this, Replit introduced Eval, a new reverse WebSocket proxy service positioned between the client and Conman.

With the new architecture, Conman can now focus solely on container management, while Eval takes full responsibility for the proxy role, resulting in the following benefits:

• Improved connection stability: Proxy connections can be maintained even during Conman updates
• Improved scalability: Independent Autoscaling based on container count is now possible
• Easier diagnostics: Separation of proxy and container management logic makes it easier to identify the cause of failures