Github user jburwell commented on the pull request:
https://github.com/apache/cloudstack/pull/1331#issuecomment-212596332
@rafaelweingartner the garbage collection issue is not the
allocation/deallocation, but the reachability calculation that the garbage
collector must perform for every instance member (i.e. determining whether or
not that instance needs to be collected). Since it, ultimately, the logger is
a singleton, this reachability check is completely unnecessary. In contrast,
the garbage collector skips this check for ``static final`` members as it is
guaranteed to be reachable for the lifetime of the JVM. While the overhead of
this check is relatively small, making logger (or any other constant values)
instance members on classes whose instances are rapidly allocated and
deallocated accrues quickly.
@syed Done properly, the appender approach can be made reusable for other
test cases to verify logging behavior. I built a [custom
appender](https://gist.github.com/jburwell/98b6d94c57f409b5b778ffee6a8a12b1)
that allows monitoring of a logger for one or more patterns and assert that
logging occurred as expected. The following is an example of how to use it in
this test case:
```
public class NfsSecondaryStorageResourceTest {
private TestAppender testAppender;
@Before
public void setup() {
testAppender = new
TestAppenderBuilder().addExpectedPattern(Level.DEBUG, "Failed to clean up
staging area:\*+").build();
Logger logger = Logger.getLogger(NfsSecondaryStorageResource.class);
TestAppender.safeAddAppender(logger, testAppender);
}
@Test
public void testSwiftWriteMetadataFile() throws Exception {
// test operations and asserts
testAppender.assertMessagesLogged();
}
```
The class likely needs a little work, and definitely, some testing. I put
it together quickly to demonstrate a reusable approach to testing logging.
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