JiaLiangC opened a new pull request, #3749:
URL: https://github.com/apache/ambari/pull/3749
## What changes were proposed in this pull request?
File Location: ambari-server/src/main/python/ambari_server/properties.py
Problem Description:
1. The `_getattr_` method is used for dynamic proxying of methods. In the
case where `hasattr(self._props, name)` is false indicating the corresponding
method or attribute cannot be found, an exception needs to be thrown. If not,
it may confuse the user and obstruct code debugging.
2. The class `Properties` proxies the `has_key` method to the `dict` object
through `_getattr`, which is acceptable: `Properties().has_key("x")`. However,
for the operation `"x" in Properties()`, it ends up in an infinite hang, never
returning. Therefore, a `contains_` method needs to be implemented to keep
consistency with the logic of `has_key`, i.e., to determine whether the object
is in `_props`:
```python
def _contains_(self, key):
return key in self._props
```
This modification prevents the infinite hang problem from occurring.
To reproduce the hang issue, we can make a simplified version of the
`Properties` class for testing, as follows:
```python
#!/usr/bin/env python
import os
import re
import time
class Properties(object):
def _init_(self, props=None):
self._props = {}
self._origprops = {}
self._keymap = {}
def get_property(self, key):
return self._props.get(key, '')
def propertyNames(self):
return self._props.keys()
def getPropertyDict(self):
return self._props
def _getitem_(self, name):
return self.get_property(name)
def _getattr_(self, name):
try:
return self._dict_[name]
except KeyError:
if hasattr(self._props, name):
return getattr(self._props, name)
else:
raise NotImplementedError("The method '{}' is not
implemented.".format(name))
def _contains_(self, key):
return key in self._props
if _name_ == "_main_":
p = Properties()
"a" in p
```
Upon running this program with either Python 3 or Python 2 python, it will
indefinitely hang, never returning.
## How was this patch tested?
manual test
unit test
(Please explain how this patch was tested. Ex: unit tests, manual tests)
(If this patch involves UI changes, please attach a screen-shot; otherwise,
remove this)
Please review [Ambari Contributing
Guide](https://cwiki.apache.org/confluence/display/AMBARI/How+to+Contribute)
before opening a pull request.
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