Add effective url options to slice plugin.

[traeak]

Initial slice plugin used pristine url to virtually call back into the same rule. This allows using a single remap line, but it has a disadvantage of rerunning all plugin rules for each slice transaction in addition to the incoming request transaction. Also it makes log analysis more difficult, the only difference being that the callback comes in on port '0'. http and https get a bit confusing as well with using the pristine url as the loopback is connected with the https url if the incoming rule is https.

This changes the default remap behaviour of the slice plugin to use a virtual remap parent point, allowing separate remap lines.

the way to set up the slice plugin with effective url: (option --remap-host= or -r )

# Base remap rule (non GET requests pass through)
map http://ats/ http://parent/ @plugin=uri_signing.so @pparam=foo_uri.config @plugin=slice.so @pparam=--remap-host=loopback

# Virtual forward proxy slice block leg (cached)
map http://loopback/ http://parent/ @plugin=header_rewrite.so @pparam=reject_non_php0.config @plugin=cache_range_requests.so

Previous configuration is still default behavior (uri_signs for incoming AND each sliced up block):

map http://ats/ http://parent/ @plugin=uri_signing.so @pparam=foo_uri.config @plugin=slice.so @plugin=cache_range_requests.so

[traeak]

Dealing with head requests for the effective url path...solve with virtual forward proxy rule...

[bryancall]

[approve ci]

[jrushford]

Looks good

[jrushford]

[approve ci ubuntu]

[jrushford]

[approve ci ubuntu]

[zwoop]

Do you want this for 9.0.x ?

[jrushford]

Yes please. From: Leif Hedstrom <notifications@github.com> Reply-To: apache/trafficserver <reply@reply.github.com> Date: Wednesday, November 13, 2019 at 8:53 PM To: apache/trafficserver <trafficserver@noreply.github.com> Cc: John Rushford <John_Rushford@cable.comcast.com>, State change <state_change@noreply.github.com> Subject: Re: [apache/trafficserver] Add effective url options to slice plugin. (#5727) Do you want this for 9.0.x ? — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub<#5727?email_source=notifications&email_token=ABCXE3R4NGGTRXDBSUQVMBTQTTDSVA5CNFSM4IEARSD2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEEAP2PQ#issuecomment-553712958>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ABCXE3SZ772AR6RPYHVKPGLQTTDSVANCNFSM4IEARSDQ>.

[zwoop]

Cherry-picked to v9.0.x branch.