[SPARK-20042] [Web UI] Fix log page buttons for reverse proxy mode

[okoethibm]

with spark.ui.reverseProxy=true, full path URLs like /log will point to
the master web endpoint which is serving the worker UI as reverse proxy.
To access a REST endpoint in the worker in reverse proxy mode , the
leading /proxy/"target"/ part of the base URI must be retained.

Added logic to log-view.js to handle this, similar to executorspage.js

Patch was tested manually

[srowen]

CC @ajbozarth

[ajbozarth]

I'm not a big fan of how difficult to read/understand getRESTEndPoint() is, but given it matches similar functionality elsewhere I say this LGTM.

[ajbozarth]

@srowen can you ok to test this?

[ajbozarth]

@srowen or @vanzin mind okaying this to test (and taking a quick look)?

[srowen]

Hm, is this the only link that needs rewriting in the presence of a proxy? it looks kind of brittle, like it depends on a quite specific URL structure. Can this be generalized? And/or can the logic be explained?

[okoethibm]

This is the only link generated from JavaScript that doesn't work at the moment. As noted above, the same kind of rewrite already takes place in executorspage.js (committed by @tgravescs, function createRESTEndPoint), that's where I copied the logic, with the dependency on /proxy/ inside the URL.
Of course it would be nicer to have this generalized somewhere -- this PR is intended as a low-risk localized bugfix, not a refactoring.

[srowen]

I see, so it's the same approach already used everywhere else and it's not easy to centralize. OK.

[okoethibm]

@srowen Can you please "ok to test" then?

[SparkQA]

Test build #3636 has finished for PR 17370 at commit 216e8fc.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

Merged to master/2.1