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### _Why are the changes needed?_
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Support expose Prometheus metrics
### _How was this patch tested?_
- [x] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [x] [Run test](https://kyuubi.readthedocs.io/en/latest/tools/testing.html#running-tests) locally before make a pull request
Closes#630 from pan3793/prometheus.
Closes#630
fff68b0 [Cheng Pan] nit
47c19eb [Cheng Pan] simplify
203e776 [Cheng Pan] address comments
10a877c [Cheng Pan] synchronized
26eb26e [Cheng Pan] simplify random port
827427c [Cheng Pan] fix import
476ee3a [Cheng Pan] address comments
9787c77 [Cheng Pan] update ut
c8e1b0e [Cheng Pan] update license
2387a97 [Cheng Pan] [METRICS] Support expose Prometheus metrics
Authored-by: Cheng Pan <379377944@qq.com>
Signed-off-by: Kent Yao <yao@apache.org>
0b4f4f242c