Improve performance of NamingConvention#toSnakeCase

[michaldo]

No description provided.

[shakuzen]

Improving the performance of this would be a nice enhancement for many users, but we need to be careful as the impact of issues here could be large.

[shakuzen]

It's subtle, but this does not have the same behavior as the previous code. See, for example, the following test on the main branch (i.e. without this code change):

@Test
void snakeCaseReplace() {
    String name = "a.Name.with.Words.";
    String expectedConventionName = "a_Name_with_Words";
    String actualConventionName;

    actualConventionName = NamingConvention.snakeCase.name(name, Meter.Type.COUNTER);
    assertThat(actualConventionName).isEqualTo(expectedConventionName);

    actualConventionName = name.replace(".", "_");
    assertThat(actualConventionName).isEqualTo(expectedConventionName);
}

The second assertion fails:

org.opentest4j.AssertionFailedError: 
expected: "a_Name_with_Words"
 but was: "a_Name_with_Words_"

It's unfortunate we don't have existing tests to cover a more complete set of expected input and output, but it would be risky to change this behavior and cause potential regressions for users.

[michaldo]

If #5288 increases performance and is more consistent with module design, I'm fine and this PR can be closed.

According to "subtle behavior change", it should be documented how metric name is changed for Prometheus. Then it will be possible to say if removing leading and trailing dots is part of contract or random side effect

[jonatan-ivanov]

I think some benchmarks (JMH) would be also nice to prove that this is in fact an improvement. Regarding #5288, this might not be the root cause since this line is there for 7 years and as far as I understand the issue is new.

[michaldo]

Here you are:

@Benchmark
 public void snakeStream(Blackhole blackhole) {
     String value = "http.client.requests.active.seconds.max";
     String snak = Arrays.stream(value.split("\\.")).filter(Objects::nonNull).collect(Collectors.joining("_"));
     blackhole.consume(snak);
 }

 @Benchmark
 public void snakeSimple(Blackhole blackhole) {
     String value = "http.client.requests.active.seconds.max";
     String snak = value.replace(".", "_");
     blackhole.consume(snak);
 }

Benchmark               Mode  Cnt         Score         Error  Units
SnakeCase.snakeSimple  thrpt   25  49690145,331 ± 3281631,270  ops/s
SnakeCase.snakeStream  thrpt   25   3717968,300 ±  101394,596  ops/s