Return http client and scheme?

[nishanttotla]

Currently, the engine-api client does not export or allow a way to get the underlying http client and scheme.

Would it be possible to add a function to do this?

[vdemeester]

Hi @nishanttotla , what would be the use case ? (/me curious 👼)

[nishanttotla]

@vdemeester in Swarm, we have this function

func closeIdleConnections(client *http.Client) {
    if tr, ok := client.Transport.(*http.Transport); ok {
        tr.CloseIdleConnections()
    }
}

that needs the http client. At a couple of other places, we also pass requests to the agent Engines directly. Perhaps @vieux or @dongluochen know better about the reasoning behind that.

[dongluochen]

There are several use cases to set HTTP client parameters:

1. Users want to set MaxIdleConnsPerHost and DisableKeepAlives to control the number of TCP connections for a cluster. The manager becomes a bottleneck in a large cluster.
2. TCP dead peer detection. If a receiver disappears abruptly, it'd take very long (15 min on Linux default settings) to detect connection failure. TCP user timeout can reduce this detection time. See Accelerate dead peer detection with user timeout option samalba/dockerclient#202.

[calavera]

You can initialize a client outside and pass it to the API:

https://github.com/docker/engine-api/blob/master/client/client.go#L69

You can do whatever you want with it without having to expose it again from within the API.

[nishanttotla]

@calavera that's pretty much what we currently do - create the client using samalba/dockerclient, then pass it on to engine-api, and were hoping to only use the latter.

[nishanttotla]

Closing this issue, because we're fixing it in Swarm: docker-archive/classicswarm#2206