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### _Why are the changes needed?_
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1. refine the zk lock to lock only during engine bootstrapping, not wrap the part that only gets the address of engines. This can significantly reduce overhead.
2. add tests for the locking proccess.
### _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#629 from yaooqinn/lock.
Closes#629
a1b4e5f1 [Kent Yao] Refine distributed lock to lock only engine bootstrap
a6738652 [Kent Yao] Refine distributed lock to lock only engine bootstrap
ff238e6f [Kent Yao] Refine distributed lock to lock only engine bootstrap
f3979fce [Kent Yao] Refine distributed lock to lock only engine bootstrap
e8ca9954 [Kent Yao] Refine distributed lock to lock only engine bootstrap
Authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Cheng Pan <379377944@qq.com>
d2be0f34e8