- Author(s): murgatroid99
- Approver: wenbozhu
- Status: In Review
- Implemented in: Node.js
- Last updated: 2023-11-09
- Discussion at: https://groups.google.com/g/grpc-io/c/-md8UlWAtKY
Add a new method drain to the Server class to gracefully close all active connections on a specific port or all ports.
gRFC A36: xDS-Enabled Servers specifies that an update to a Listener resource causes all older connections on that Listener to be gracefully shut down with a grace period for long-lived RPCs.
A single method drain(port: string, graceTimeMs: number): void will be added to the Server class. When called, all open connections associated with the specified port will be closed gracefully. After graceTimeMs milliseconds, all open streams on those connections will be cancelled.
The port string will be handled the same as in gRFC L109: the name will be normalized, and then used to reference the existing list of bound ports. Port 0 is handled specially: a call to drain with port 0 will throw an error. After a call to bindAsync with a port number of 0 succeeds, and the specific bound port number is provided in the callback, drain can be called with the original port string with the bound port number substituted for port 0 to drain connections on that port.
When implementing gRFC A36, I intend to make the xDS server a subclass of the Server class. TypeScript supports using the protected keyword to make fields visible to subclasses. So, it would be possible to make the relevant internals protected to be able to implement this functionality directly in the xDS server class. However, doing so makes those fields visible to any user that wants to subclass Server, effectively making them part of the library's public API. That would put significant limits on how those fields could change in the future, which I am not currently willing to accept.
The specific use case described in gRFC A36 only calls for draining a specific port, and the grace period is always applied, so the API defined here fully handles that use case. The arguments could be made optional
I (murgatroid99) will implement this.