Port legacy perl TO extension checks from perl to go

[guzzijason]

What does this PR (Pull Request) do?

• This change ports (most) of the legacy perl server checks to go.
• Performance (and logic problems) of the original DSCP check script was the primary motivation - in our environment, the DSCP scan was taking ~20 hours to run, and the results were unreliable.
• ADD support for performing DSCP checks of SSL delivery services, which was previously missing.
• ADD option to FQDN check for validating PTR records
• Other scripts were ported over for sake of consistency.

Standalone programs only, and no changes are made to existing Traffic Ops API components, hence no integrated testing is included.

Which Traffic Control components are affected by this PR?

• Traffic Ops Extensions (server checks)

What is the best way to verify this PR?

If this is a bug fix, what versions of Traffic Control are affected?

The following criteria are ALL met by this PR

• [x] This PR includes tests OR I have explained why tests are unnecessary
• [x] This PR includes documentation OR I have explained why documentation is unnecessary
• [x] This PR includes an update to CHANGELOG.md OR such an update is not necessary
• [x] This PR includes any and all required license headers
• [x] This PR ensures that database migration sequence is correct OR this PR does not include a database migration
• [x] This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information

[asf-ci]

Can one of the admins verify this patch?

[ocket8888]

What's the motivation for this? Check extensions just run as scripts with no actual dependency on the Perl TO codebase, right?

[ocket8888]

ok to test

[guzzijason]

@ocket8888 I just emailed the dev/users lists with some more info regarding motivation.

The only dependency was an update to the go client library (https://github.com/apache/trafficcontrol/pull/3470) which has already been merged.

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4607/

[smalenfant]

Can we add those to the Traffic Ops build? Would be nice to be available and compiled when installing traffic_ops RPM.

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4644/

[guzzijason]

Do not merge - there were changes in ccff78a that broke the code in this PR, that I was not anticipating. I need to sort that out now.

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4654/

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4656/

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4659/

[guzzijason]

I'm satisfied that the code in this PR is now building and running satisfactorily with the go client library version that are in currently master.

[asf-ci]

Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/trafficcontrol-PR/4660/

[ocket8888]

Can you rebase to fix those conflicts?

I also think you probably have a better chance of getting this reviewed if each extension is a separate PR, but that's just my opinion.

[smalenfant]

@guzzijason Can we rebase this on master again please? Some issues with the Traffic Ops client versioning (my guess)

[guzzijason]

@smalenfant yes, I've recently updated the ones we're using internally here. I'll work on updating this PR.

[smalenfant]

@guzzijason In light of TC 6 to remove the API 1.x API, could we resolve the conflict on this one?

[smalenfant]

How do we build those components? I tried to "wget" them but I can't figure how to compile them. I would like to install them on a different server than my Traffic Ops as well.

[smalenfant]

It actually looks like they would be packaged in the Traffic Ops RPM. But the build failed.

github.com/apache/trafficcontrol/traffic_ops/app/bin/checks imports
	github.com/apache/trafficcontrol/traffic_ops/client: no matching versions for query "latest"
+ echo 'Could not vendor go module dependencies'

[ocket8888]

The unversioned client import path was deprecated in 4.0 or 4.1 and disabled/removed in 5.0, I believe. Needs to add a version prefix - should probably just use v4- since it's packaged with TO.