[SPARK-8405][Doc] Add how to view logs on Web UI when yarn log aggregation is enabled

[carsonwang]

Some users may not be aware that the logs are available on Web UI even if Yarn log aggregation is enabled. Update the doc to make this clear and what need to be configured.

[SparkQA]

Test build #37617 has finished for PR 7463 at commit e5775c1.

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

[srowen]

Minor text updates: MR history server -> MapReduce History Server. I'd hyperlink one of them too. url -> URL. back-tick yarn-site.xml It would be nice to link through to YARN docs that would describe these parameters too, if possible.

[carsonwang]

Thanks @srowen . I updated the text. But I didn't find proper docs for MapReduce job history server and the yarn.log.server.url parameter on apache site. So I didn't add links. If a user search these, he will find necessary information on other websites.

[SparkQA]

Test build #37789 has finished for PR 7463 at commit 5a95046.

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

[tgravescs]

"The logs are also available on Web UI" is pretty generic. Can we make this more specific like on the Spark Web UI under the Executors Tab

[carsonwang]

Sounds great, @tgravescs . The text was updated as you suggested.

[SparkQA]

Test build #38044 has finished for PR 7463 at commit 74df3a1.

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

[tgravescs]

can you change "You need have" to "You need to" have"

[tgravescs]

one minor nit, otherwise looks good. @srowen do you have any other comments, I want to not sure your previous comment was addressed?

[srowen]

OK by me

[carsonwang]

Sorry for the delay. Updated!

[SparkQA]

Test build #38427 has finished for PR 7463 at commit 274c054.

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

[tgravescs]

+1. Thanks!