guides/http: document Java Jetty client integration

[odeke-em]

Document the Java Jetty client integration with a guide,
an end-to-end example and screenshots.

Updates #562

[rghetia]

Looks good. Couple of things.

1. Would it not be better to use same example as it is in the repo. If the example in repo is not sufficient then we can enhance or change.
2. An example with client and server both would be better than standalone client.

[odeke-em]

Thank you for listing out your concerns @rghetia! Please see my responses below:

1. Would it not be better to use same example as it is in the repo. If the example in repo is not sufficient then we can enhance or change.

The example in the OpenCensus-Java repo is a full copy and pastable example for both the server and client but here we are documenting step by step for those who just want to use the client integration and the same for those who want to use the server integration. Otherwise, we'd just be dumping for them source code to go inspect. Please see what we've done for Go's net/http https://opencensus.io/guides/http/go/net_http/

An example with client and server both would be better than standalone client.

Sure for running source code but not for prescriptive steps when users are integrating it to parts of their apps, when someone just wants to focus on the client, them reverse engineering source code yet not everyone runs both client and server.

[rghetia]

I didn't mean to dump the source code from the example directory but rather use code snippets from the example directory. Your step by step instructions are great.

[odeke-em]

I didn't mean to dump the source code from the example directory but rather use code snippets from the example directory. Your step by step instructions are great.

Oh I see. You have great examples in the OpenCensus-Java repo, but for this guide, the differences that I made were:
a) not using the log4j logger
b) used two different URLs to demonstrate it capturing status codes: 200 and 404 by fetching from https://opencensus.io/community and https://opencensus.io/non-existent respectively which are then shown in the trace and stats screenshots to demonstrate how the integration enhances and captures observability from requests

[rghetia]

what about gradle?

[odeke-em]

Roger that, I've added:

• Gradle
• Buildr
• Ivy

for the minimum additions of *http-jetty-client and *http-util dependencies.

[rghetia]

I didn't mean to dump the source code from the example directory but rather use code snippets from the example directory. Your step by step instructions are great.

Oh I see. You have great examples in the OpenCensus-Java repo, but for this guide, the differences that I made were:
a) not using the log4j logger
b) used two different URLs to demonstrate it capturing status codes: 200 and 404 by fetching from https://opencensus.io/community and https://opencensus.io/non-existent respectively which are then shown in the trace and stats screenshots to demonstrate how the integration enhances and captures observability from requests

SG.

[odeke-em]

Please take a look at the update @rghetia and thanks for the initial review!

[rghetia]

LGTM

[odeke-em]

Thank you for the review @rghetia!