No user-agent set when communicating via proxy

[abatkin]

Expected Behavior

When communicating via an explicit (non-transparent) HTTP Proxy, the User-Agent header should be set to something like aws-sdk-java/whatever... (see UserAgentUtils.UA_STRING for the template)

Current Behavior

The User-Agent header is set to an empty string:

http-outgoing-1 >> "CONNECT sts.us-east-1.amazonaws.com:443 HTTP/1.1[\r][\n]"
http-outgoing-1 >> "Host: sts.us-east-1.amazonaws.com[\r][\n]"
http-outgoing-1 >> "User-Agent: [\r][\n]"
http-outgoing-1 >> "[\r][\n]"
http-outgoing-1 << "HTTP/1.1 200 Connection established[\r][\n]"
http-outgoing-1 << "[\r][\n]"

I believe this is due to the .setUserAgent("") in ApacheHttpClient.createClient().

Possible Solution

It would be nice for the User-Agent header to be set to something sensible in the client itself instead of the empty string (as outlined above). Later on in the (normal) request processing, the AWS SDK will set the User-Agent header itself, but that's only for the portion of the request that it actually handles (i.e. the SDK explicitly sets the header when making a request, whereas the setUserAgent() sets a property on the client itself, and that property is needed by HttpClient when talking to a proxy).

Steps to Reproduce (for bugs)

1. Set up a proxy server
2. Tell the SDK to use the proxy (either using the JDK standard System Properties or by setting proxyConfiguration() on the ApacheHttpClient's builder)
3. Make a request to an AWS service (I used STS)
4. Notice that an empty string is sent for the User-Agent header (either by looking at the HttpClient's debug logs, or asking the proxy server to dump the traffic)

Context

Proxy servers may handle requests different depending on a number of factors, including the User Agent. Without an accurate User Agent header, proxy servers lose an important piece of information.

Your Environment

• AWS Java SDK version used: 2.9.14
• JDK version used: 1.8.x
• Operating System and version: Windows

[dagnir]

Thanks @abatkin. This applies to the Netty client and probably the URL connection client as well.

[h-hub]

@zoewangg Since this is tagged with hacktoberfest, can I give this a try?

[zoewangg]

@h-hub Absolutely! 😃 PRs are always welcome!

[h-hub]

Thanks @zoewangg 😃