carterkozak commented on a change in pull request #289: LOG4J2-2644 - Improve
performance of getting location info
URL: https://github.com/apache/logging-log4j2/pull/289#discussion_r298841455
##########
File path:
log4j-api-java9/src/main/java/org/apache/logging/log4j/util/StackLocator.java
##########
@@ -72,15 +78,40 @@ private StackLocator() {
}
public StackTraceElement calcLocation(final String fqcnOfLogger) {
- return stackWalker.walk(
- s -> s.dropWhile(f -> !f.getClassName().equals(fqcnOfLogger))
// drop the top frames until we reach the logger
- .dropWhile(f -> f.getClassName().equals(fqcnOfLogger))
// drop the logger frames
- .findFirst())
- .get()
- .toStackTraceElement();
+ return walker.walk(s ->
s.filter(LOCATOR.get().setFqcn(fqcnOfLogger)).findFirst()).get().toStackTraceElement();
Review comment:
We may want `CallerLocator` to implement
`Function<Stream<StackWalker.StackFrame>, Optional<StackWalker.StackFrame>>` to
avoid the lambda allocation for `s ->
s.filter(LOCATOR.get().setFqcn(fqcnOfLogger)).findFirst()`
```suggestion
return
walker.walk(LOCATOR.get().setFqcn(fqcnOfLogger)).get().toStackTraceElement();
```
using something like this:
```java
static final class CallerLocator implements
Predicate<StackWalker.StackFrame>,
Function<Stream<StackWalker.StackFrame>,
Optional<StackWalker.StackFrame>> {
private String fqcn;
private boolean foundFqcn = false;
private boolean foundLogger = false;
CallerLocator setFqcn(String fqcn) {
this.fqcn = fqcn;
this.foundFqcn = false;
this.foundLogger = false;
return this;
}
@Override
public boolean test(StackWalker.StackFrame t) {
final String className = t.getClassName();
if (!foundLogger) {
if (!foundFqcn) {
foundFqcn = className.equals(fqcn);
return false;
} else if (!className.equals(fqcn)) {
foundLogger = true;
return true;
}
}
return false;
}
@Override
public Optional<StackWalker.StackFrame>
apply(Stream<StackWalker.StackFrame> stackFrameStream) {
return stackFrameStream.filter(this).findFirst();
}
}
```
I'm not sure how much that helps if at all, I haven't looked into how much
allocation StackWalker does internally.
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