LoggentriesAppender: memory efficient concatenation for layout.ignoresThrowable()

[jcodagnone]

Allocate just the right amount of characters once.

Before this change the stack gets concatenated using the string concatenation operator.
In such scenery, the optimization proposed on JLS-15.18.1 may not apply to the code valid
(it is not a one liner).

Oracle 1.8.0_77 i7-4510U CPU @ 2.00GHz, for 60 deep stacktrace exception ("a typical exception")

Legacy code (extracted as an static method):

  n:           98,999
  min:        210,397 nanoseconds
  max:      5,640,727 nanoseconds
  mean:       256,441 nanoseconds
  std dev:     68,782 nanoseconds
  median:     242,984 nanoseconds

After:

  n:           98,999
  min:          2,555 nanoseconds
  max:      2,930,444 nanoseconds
  mean:         5,038 nanoseconds
  std dev:     22,034 nanoseconds
  median:       3,803 nanoseconds

Methodology:

  final int n = 100000;
  final DescriptiveStatistics statistics = new DescriptiveStatistics(n);
  final String []stack = {
     // ....
  };
  for (int i = 0 ; i < n ; i++) {
    final long t0 = System.nanoTime();
    LogentriesAppender.appendFormatedEvent("fooo", stack);
    final long t1 = System.nanoTime();
    if(i > 1000) {
      statistics.addValue(t1-t0);
    }
  }
  System.out.println(statistics);

DescriptiveStatistics is provided by org.apache.commons:commons-math:2.2

[danilosterrapid7]

There are some things that might saved more cpu cycles here.
Replacing:

int buffSize = formattedEvent.length();
buffSize += EXCEPTION_SEPARATOR.length();

By:

int buffSize = formattedEvent.length() + EXCEPTION_SEPARATOR.length();

And removing from the loop:

if (i < len - 1) {
    buffSize += 1;
}

And adding after for loop:

buffSize += len - 1;

It would save... ;)

[jcodagnone]

@danilosterrapid7 you are right! commit updated!

[m0wfo]

@jcodagnone before doing any more hating, are you running this on Android?

[jcodagnone]

@m0wfo no, I'm not running it on Android (but I know that StringBuilder is available there), why you ask?

I was reviewing the library before adding it to a project because I wanted to understand if it may block program if the network was slow; and I saw these possibles enhances.

[danilosterrapid7]

@scawley-r7 a bit ashamed, I really have forgot it. Besides, no one checked it out either. Is it ok to get it merged if you do not have any comment on that?

[danilosterrapid7]

@stopal-r7 ^^^