Setting proxy parameters is not flexible enough

[denchenko]

Please answer these questions before submitting your issue.

What version of gRPC are you using?

bfaf042

What version of Go are you using (go version)?

go version go1.8.3 linux/amd64

What operating system (Linux, Windows, …) and version?

Linux

What did you do?

There are multiple grpc connections in my project at one time. One of them need proxy, another not. Proxy require credentials.

What did you see?

Currently, grpc-go takes proxy settings from ENV only once at the start of binary. In addition, it is a little bit buggy. It takes only host and ignores credentials.

What did you expect to see?

I want

• use credentials with proxy
• possibility to change proxy in runtime. Since grpc-go takes it only once from env, so it will be enough to add optional parameter ProxyURL. If it is not exist, then use value from ENV

[denchenko]

I am developing these features and will send PR today.

[EdSchouten]

It would have made sense if there was a grpc.WithProxy() or something that took a callback that has the same signature as http.ProxyFromEnvironment and http.ProxyURL. For a project of mine (bb-storage) it's a bit wacky that all of the gRPC settings are done through a config file, except for the proxy. That can only be configured through an environment variable.

[dfawley]

For more complex dialing protocols that don't work with our built-in proxy support, we would recommend using the WithContextDialer dial option.

[EdSchouten]

@dfawley If gRPC for Go is not going to provide any more flexible ways for doing this, could source file internal/transport/proxy.go please be released under the public domain? That way people copy-paste all of that code for their purpose. As all of that needs to be duplicated because of it. Thanks!

[dfawley]

As part of the CNCF, I believe we are required to keep this license on all code contributed to the project. Note that the terms for the Apache license we use are very flexible, so if you don't want to reimplement it yourself, you can still reuse it directly as long as you follow the requirements.