Oauth2 support in HTTP output plugin

[vikrant6]

Support for OAuth2 Authentication in http output plugin.
The golang client credentials librarty supports token reuse untill its expiry.

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[vikrant6]

fmt check done

[vikrant6]

dep ensure -vendor-only fixed

[vikrant6]

fixed test errors

[vikrant6]

test

[danielnelson]

@vikrant6 Thanks for the PR. I'll try to take a look soon, ping me when you have the tests passing on circleci or if you need help.

[vikrant6]

@danielnelson I very new to go and might be missing something basic here. Need your help

go vet $(go list ./... | grep -v ./plugins/parsers/influx)
plugins/outputs/http/http.go:17:2: cannot find package "golang.org/x/oauth2" in any of:
/go/src/github.com/influxdata/telegraf/vendor/golang.org/x/oauth2 (vendor tree)
/usr/local/go/src/golang.org/x/oauth2 (from $GOROOT)
/go/src/golang.org/x/oauth2 (from $GOPATH)
plugins/outputs/http/http.go:18:2: cannot find package "golang.org/x/oauth2/clientcredentials" in any of:
/go/src/github.com/influxdata/telegraf/vendor/golang.org/x/oauth2/clientcredentials (vendor tree)
/usr/local/go/src/golang.org/x/oauth2/clientcredentials (from $GOROOT)
/go/src/golang.org/x/oauth2/clientcredentials (from $GOPATH)

[danielnelson]

This error is due to the new dependency not being added to the lock file. You don't want to edit it by hand though, undo your changes to Gopkg.toml and run:

dep ensure -add golang.org/x/oauth2@master

Then make sure there are no errors when you run:

dep check

[vikrant6]

@danielnelson Thanks. vet is failing for some packages (existing) Any idea how to proceed?

[vikrant6]

@danielnelson - Any pointer on how to proceed from here?

[danielnelson]

@vikrant6 Is it alright if I fix it up and push to your fork?

[vikrant6]

@danielnelson - Please go ahead. Thanks.

[danielnelson]

I fixed up the dep issue, cleaned up some whitespace changes, and switch the client over to using the oauth2.Client and added some tests. I made some minor tweaks to the config file variable names as well.

Here is the rpm from CircleCI telegraf-1.8.0~f6efa1a9-0.x86_64.rpm

[vikrant6]

@danielnelson Thank you !

[vikrant6]

@danielnelson What's next for this to merge ? Is there a milestone identified?

[danielnelson]

We should be able to add this to 1.8. Since I don't have a real system to do a final testing, can you let me know if everything is working?

[vikrant6]

@danielnelson Found that it no longer honors the configuration "insecure_skip_verify=true"
For self signed certs it errors out as "x509: certificate signed by unknown authority"
I can test the windows and linux version extensively here.

[danielnelson]

I think this will fix it: c1dc2d0

Updated package: telegraf-1.8.0~c1dc2d06-0.x86_64.rpm