First implementation of benchmark

logstash-core/benchmarks/src/main/java/org/logstash/benchmark/DeadLetterQueueUtilsBenchmark.java

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+package org.logstash.benchmark;
+
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.nio.file.Path;
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+@Warmup(iterations = 3, time = 100, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 10, time = 3000, timeUnit = TimeUnit.MILLISECONDS)
+@Fork(1)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@State(Scope.Thread)
+public class DeadLetterQueueUtilsBenchmark {
+
+    private Path path;
+    private static final Pattern precompiledPattern = Pattern.compile("^([0-9]+)\\.log$");
+
+    @Setup(Level.Invocation)
+    public void setUp() {
+        path = Path.of("1234567890.log");
+    }
+
+    @Benchmark
+    public final void splitWithPlainRegExp(Blackhole blackhole) {
+        int i = extractWithPlainRegExp(path);
+        blackhole.consume(i);
+    }
+
+    static int extractWithPlainRegExp(Path p) {
+        return Integer.parseInt(p.getFileName().toString().split("\\.log")[0]);
+    }
+
+    @Benchmark
+    public final void splitWithImprovedRegExp(Blackhole blackhole) {
+        int i = extractWithImprovedRegExp(path);
+        blackhole.consume(i);
+    }
+
+    static int extractWithImprovedRegExp(Path p) {
+        Pattern pattern = Pattern.compile("^([0-9]+)\\.log$");
+        Matcher matcher = pattern.matcher(p.getFileName().toString());
+        matcher.find();
+
+        String filename = matcher.group(1);
+
+        return Integer.parseInt(filename);
+    }
+
+    @Benchmark
+    public final void splitWithImprovedRegExp_precompiledRegExp(Blackhole blackhole) {
+        int i = extractWithImprovedRegExp_precompiledRegExp(path);
+        blackhole.consume(i);
+    }
+
+    static int extractWithImprovedRegExp_precompiledRegExp(Path p) {
+        Matcher matcher = precompiledPattern.matcher(p.getFileName().toString());
+        matcher.find();
+
+        String filename = matcher.group(1);
+
+        return Integer.parseInt(filename);
+    }
+
+    @Benchmark
+    public final void splitWithIndexOf(Blackhole blackhole) {
+        int i = extractWithIndexOf(path);
+        blackhole.consume(i);
+    }
+
+    static int extractWithIndexOf(Path p) {
+        final String fileName = p.getFileName().toString();
+        final int dotIndex = fileName.indexOf(".log");
+        return Integer.parseInt(fileName.substring(0, dotIndex));
+    }
+}

logstash-core/src/test/java/org/logstash/common/io/DeadLetterQueueUtilsTest.java

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+package org.logstash.common.io;
+
+import org.junit.Test;
+
+import java.nio.file.Path;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import static org.junit.Assert.*;
+
+public class DeadLetterQueueUtilsTest {
+
+    @Test
+    public void testExtractSegmentIdWithImprovedRegExp() {
+        assertEquals(1234567890, extractWithImprovedRegExp(Path.of("1234567890.log")));
+        assertEquals(0, extractWithImprovedRegExp(Path.of("0.log")));
+        assertEquals(42, extractWithImprovedRegExp(Path.of("42.log")));
+    }
+
+    static int extractWithImprovedRegExp(Path p) {
+        Pattern pattern = Pattern.compile("^([0-9]+)\\.log$");
+        Matcher matcher = pattern.matcher(p.getFileName().toString());
+        matcher.find();
+
+        String filename = matcher.group(1);
+
+        return Integer.parseInt(filename);
+    }
+}