Proxy from environment not working

[Fra-nk]

#92 added support for using proxy variables (HTTP_PROXY, HTTPS_PROXY & NO_PROXY) from the environment.
#173 removed this feature

This is not documented in the 0.6.0 release notes, so I assume it is a bug?

[brian-brazil]

As a general Prometheus principle, we don't technically support configuration from anything other than the config file. I will accept a PR to fix that over in common though.

[brian-brazil]

Actually the current behaviour matches Prometheus, so it'd be best to keep in sync.

[Fra-nk]

Well I'll happily submit a pull request, if there is a reasonable chance of getting it implemented.
So after the second comment I want to know if it's worth sending the pull request at all?

Just tested it successfully with directly modifying the vendored dependencies, but it's just copy, paste and a pull request to submit it to common:

diff --git vendor/github.com/prometheus/common/config/http_config.go vendor/github.com/prometheus/common/config/http_config.go
index ff5837f..5ff5668 100644
--- vendor/github.com/prometheus/common/config/http_config.go
+++ vendor/github.com/prometheus/common/config/http_config.go
@@ -121,9 +121,16 @@ func NewHTTPClientFromConfig(cfg *HTTPClientConfig) (*http.Client, error) {
                return nil, err
        }

+       var proxyFunc func(*http.Request) (*url.URL, error)
+       if cfg.ProxyURL.URL != nil {
+               proxyFunc = http.ProxyURL(cfg.ProxyURL.URL)
+       } else {
+               proxyFunc = http.ProxyFromEnvironment
+       }
+
        // It's the caller's job to handle timeouts
        var rt http.RoundTripper = &http.Transport{
-               Proxy:             http.ProxyURL(cfg.ProxyURL.URL),
+               Proxy:             proxyFunc,
                DisableKeepAlives: true,
                TLSClientConfig:   tlsConfig,
        }

Imho there are some more complex setups where the option of setting the values as environment variables may be beneficial, especially because of the presence/evaluation of NO_PROXY.
In general, explicitly defining the proxy in the module/configuration file is the better approach, though.

[brian-brazil]

We're keeping in sync with Prometheus, so the place to try to get this changed this is in Prometheus.

In general though, the config file is how you're meant to specify things.