Support namespace API

[tisonkun]

It's convenient to put/get keys in a "namespace" for separating different usage, or it's even required to smoothly write concurrent tests share the same etcd cluster.

This concept, in ZooKeeper, is named as Chroot. I don't find it in etcd but it should be a client-side feature. I create this issue for discussing whether it's desired to implement in this crate.

The API should affect only the constructors for accepting a chroot parameter/options:

Client::connect(endpoints, chroot /* String */, options);
Client::connect(endpoints, options); // chroot in options

... and all the keys pass to this client will be prepended with the "chroot".

[davidli2010]

This crate is just an etcd api wrapper, it does not support features that etcd not support. If chroot is a client-side feature, then you can implement a KeyWrapper in your application.

[tisonkun]

Make sense. I'll wrap it in the application :D

[tisonkun]

And I found that #68 is useful to support this feature in client-side - may you take a look? #68 should be in the scope of this project.

[davidli2010]

And I found that #68 is useful to support this feature in client-side - may you take a look? #68 should be in the scope of this project.

I have already reviewed it.

[tisonkun]

@davidli2010 a possible argue is that etcd's client library implement namespace which is exactly what proposed here.

Do you think the namespace API is reasonable to be in the scope of this crate?

Ref - https://github.com/etcd-io/etcd/blob/v3.5.10/client/v3/namespace/doc.go

[davidli2010]

@davidli2010 a possible argue is that etcd's client library implement namespace which is exactly what proposed here.

Do you think the namespace API is reasonable to be in the scope of this crate?

Ref - https://github.com/etcd-io/etcd/blob/v3.5.10/client/v3/namespace/doc.go

I'd like to reivew a PR of the namespace API.

[tisonkun]

@davidli2010 Thanks for your reply! Then let's reopen this issue first, as it's valid.

I'll try to implement it, but it's not on my priority task list, so anyone please feel free to take it over.