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Avoid allocation of iterator with Tags#empty instance #3313

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merged 2 commits into from
Jul 26, 2022
Merged

Avoid allocation of iterator with Tags#empty instance #3313

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f6f3c5e
Avoid allocation of iterator with Tags#empty instance
shakuzen Jul 25, 2022
1f8c6ad
Allocation tests
shakuzen Jul 26, 2022
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4 changes: 2 additions & 2 deletions micrometer-core/src/main/java/io/micrometer/core/instrument/Tags.java
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ public Tags and(@Nullable Tag... tags) {
* @return a new {@code Tags} instance
*/
public Tags and(@Nullable Iterable<? extends Tag> tags) {
if (tags == null || !tags.iterator().hasNext()) {
if (tags == null || tags == EMPTY || !tags.iterator().hasNext()) {
return this;
}

Expand Down Expand Up @@ -216,7 +216,7 @@ public static Tags concat(@Nullable Iterable<? extends Tag> tags, @Nullable Stri
* @return a new {@code Tags} instance
*/
public static Tags of(@Nullable Iterable<? extends Tag> tags) {
if (tags == null || !tags.iterator().hasNext()) {
if (tags == null || tags == EMPTY || !tags.iterator().hasNext()) {
return Tags.empty();
}
else if (tags instanceof Tags) {
Expand Down
47 changes: 43 additions & 4 deletions micrometer-core/src/test/java/io/micrometer/core/instrument/TagsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,12 +15,13 @@
*/
package io.micrometer.core.instrument;

import com.sun.management.ThreadMXBean;
import io.micrometer.core.Issue;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.condition.DisabledIfSystemProperty;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.lang.management.ManagementFactory;
import java.util.*;
import java.util.stream.Stream;

import static org.assertj.core.api.Assertions.assertThat;
Expand All @@ -36,6 +37,9 @@
*/
class TagsTest {

// Should match "Eclipse OpenJ9 VM" and "IBM J9 VM"
private static final String JAVA_VM_NAME_J9_REGEX = ".*J9 VM$";

@Test
void dedup() {
assertThat(Tags.of("k1", "v1", "k2", "v2")).containsExactly(Tag.of("k1", "v1"), Tag.of("k2", "v2"));
Expand Down Expand Up @@ -285,6 +289,41 @@ void emptyShouldNotContainTags() {
assertThat(Tags.empty().iterator()).isExhausted();
}

@Test
@Issue("#3313")
@DisabledIfSystemProperty(named = "java.vm.name", matches = JAVA_VM_NAME_J9_REGEX,
disabledReason = "Sun ThreadMXBean with allocation counter not available")
void andEmptyDoesNotAllocate() {
ThreadMXBean threadMXBean = (ThreadMXBean) ManagementFactory.getThreadMXBean();
long currentThreadId = Thread.currentThread().getId();
Tags tags = Tags.of("a", "b");
Tags extraTags = Tags.empty();

long allocatedBytesBefore = threadMXBean.getThreadAllocatedBytes(currentThreadId);
Tags combined = tags.and(extraTags);
long allocatedBytes = threadMXBean.getThreadAllocatedBytes(currentThreadId) - allocatedBytesBefore;

assertThat(combined).isEqualTo(tags);
assertThat(allocatedBytes).isZero();
}

@Test
@Issue("#3313")
@DisabledIfSystemProperty(named = "java.vm.name", matches = JAVA_VM_NAME_J9_REGEX,
disabledReason = "Sun ThreadMXBean with allocation counter not available")
void ofEmptyDoesNotAllocate() {
ThreadMXBean threadMXBean = (ThreadMXBean) ManagementFactory.getThreadMXBean();
long currentThreadId = Thread.currentThread().getId();
Tags extraTags = Tags.empty();

long allocatedBytesBefore = threadMXBean.getThreadAllocatedBytes(currentThreadId);
Tags of = Tags.of(extraTags);
long allocatedBytes = threadMXBean.getThreadAllocatedBytes(currentThreadId) - allocatedBytesBefore;

assertThat(of).isEqualTo(Tags.empty());
assertThat(allocatedBytes).isZero();
}

private void assertTags(Tags tags, String... keyValues) {
Iterator<Tag> actual = tags.iterator();
Iterator<String> expected = Arrays.asList(keyValues).iterator();
Expand Down