How to watch using http api in python?

[Summer Wang]

No sure if it's the right place to ask. I want to make a python client using http api(there are too many dependencies using grpcio), tried several methods but seems all not work with grpc-gateway.

Do anybody have examples successfully watch etcdv3 using http api? thanks....

[anthony...@coreos.com]

Hi,

The way to do it with curl (on key="foo") is:

curl http://localhost:2379/v3alpha/watch -X POST -d '{"create_request": {"key":"Zm9v"} }

However, it seems grpc-gateway will cancel the stream once the post request is completely sent; curl will exit before the watch receives any updates. I submitted a PR to grpc-gateway upstream with a potential fix.

[Aleksandr Kuzminsky]

Sorry for offtopic, but what is it etcdv3 API and how is it different from https://coreos.com/etcd/docs/latest/api.html ?

On 11/15/16 8:03 PM, Summer Wang wrote:

No sure if it's the right place to ask. I want to make a python client using http api(there are too many dependencies using grpcio), tried several methods but seems all not work with grpc-gateway.

Do anybody have examples successfully watch etcdv3 using http api? thanks....

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[anthony...@coreos.com]

That's the v2 API; it uses a json protocol. The v3 API is complete data model revamp (cf. https://coreos.com/etcd/docs/latest/dev-guide/api_reference_v3.html); it natively uses grpc but etcd also exposes a grpc gateway on `/v3alpha` to provide the grpc API through json requests as well. etcd 3.0.0 and newer supports both v2 and v3 APIs.

https://coreos.com/blog/etcd3-a-new-etcd.html gives an overview of the high-level differences.

[tobias.o...@gmail.com]

It seems I am missing something important: the curl line below returns immediately (it doesn't sit and wait for a change).

I would have expected the HTTP/REST gateway of etcd3 to leave the HTTP/POST request "open" (similar to long-polling) - not?

I tried the latest release (3.0.16) and the current release candidate (3.1-rc1) - same behavior.

So how do I do a watch using curl and on etcd3 with the HTTP/REST gateway?

Ultimately, I want to access etcd3 from Python/Twisted - and I don't want to use gRPC for reasons.

Any hint would be greatly appreciated,

Cheers,
/Tobias

[tobias.o...@gmail.com]

> However, it seems grpc-gateway will cancel the stream once the post request is completely sent; curl will exit before the watch receives any updates.

This one?

https://github.com/grpc-ecosystem/grpc-gateway/pull/262

Was closed without merging ..

How do I do a watch on etcd3 using curl? Can't get it working ..

Am Donnerstag, 17. November 2016 01:37:00 UTC+1 schrieb anthony...@coreos.com:

[anthony...@coreos.com]

Hi,

This was fixed in 9a20743190a796b6e22184d88936dbe8ff7cb056 on November 17th. It's available in master will be included in the 3.1 release.

There is now also a grpc-gateway watch example included in the documentation: https://github.com/coreos/etcd/blob/master/Documentation/dev-guide/api_grpc_gateway.md

[Tobias Oberstein]

> This was fixed in 9a20743190a796b6e22184d88936dbe8ff7cb056 on November
> 17th. It's available in master will be included in the 3.1 release.

Ahh, thanks!

3.1-rc1 does NOT contain this commit .. I just built from master, and it
works. Thanks.

>
> There is now also a grpc-gateway watch example included in the
> documentation:
> https://github.com/coreos/etcd/blob/master/Documentation/dev-guide/api_grpc_gateway.md

Yeah, I trying that .. it might be worth having a note in this doc that
it requires etcd 3.1 release (or master). I lost like 2h trying and
wondering ..

Cheers,
/Tobias