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Improve performance of NamingConvention#toSnakeCase #5271

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Improve performance of NamingConvention#toSnakeCase #5271

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Improve performance of NamingConvention#toSnakeCase
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@michaldo
michaldo authored Jul 3, 2024
commit 264cdd5a3c6309a4e88f93f585639f22767e069c
2 changes: 1 addition & 1 deletion micrometer-core/src/main/java/io/micrometer/core/instrument/config/NamingConvention.java
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,7 @@ public String tagKey(String key) {
}

private String toSnakeCase(String value) {
return Arrays.stream(value.split("\\.")).filter(Objects::nonNull).collect(Collectors.joining("_"));
return value.replace(".", "_");
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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.

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@michaldo michaldo Jul 8, 2024 •
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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

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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.

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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

}
};

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