[takeda]

It still feels like a hack instead doing it properly. You're doing long pool instead what you should do in first place, which is push.

Again, I did not work with etcd yet, but in consul because it's "RESTful" i when you monitor multiple services you need to maintain multiple requests.

Edit: Reading more about http 2's frames and pipelining, looks like it's possible to use it similar way it's done in ZK[1]. If GRPC allows that then I suppose it indeed solves this problem.

[1] having a single long standing connection that's not closed after receiving a response. The request frames could be used to place watches and response frames would send the updates to the client.

[ideal0227]

etcd use bi-directional streams for watchers. One. TCP connections can maintains multiple streams. No matter what you need to keep at least one connection. ZooKeeper is not an exception.

[takeda]

That's good to hear. Seems like that would work the same way then.