[HADOOP-8922] Provide alternate JSONP output for JMXJsonServlet to allow javascript in browser dashboard

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 2.0.0-alpha
• Fix Version/s: 2.0.3-alpha
• Component/s: metrics
• Labels: newbie patch
• Release Note: Add a JSONP alternative outpout for /jmx HTTP interface to provide a Javascript polling ability in browsers.
• Tags: jsonp metrics jmx
• Assignee: Damien Hardy
• Reporter: Damien Hardy
• Created: 12/Oct/12 16:09
• Updated: 03/Sep/14 23:11
• Resolved: 16/Oct/12 21:42

Description

JMXJsonServlet may provide a JSONP alternative to JSON to allow javascript in browser GUI to make requests.
For security purpose about XSS, browser limit request on other domain¹ so that metrics from cluster nodes cannot be used in a full js interface.
An example of this kind of dashboard is the bigdesk² plugin for ElasticSearch.

In order to achieve that the servlet should detect a GET parameter (callback=xxxx) and modify the response by surrounding the Json value with "xxxx(" and ");" ³
value "xxxx" is variable and should be provide by client as callback parameter value.

[1] https://developer.mozilla.org/en-US/docs/Same_origin_policy_for_JavaScript
[2] https://github.com/lukas-vlcek/bigdesk
[3] http://en.wikipedia.org/wiki/JSONP