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feat: add MetricMetadata.Builder, deprecate wide constructors #2202

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18aeab7
feat: add MetricMetadata.Builder, deprecate wide constructors
zeitlinger Jun 8, 2026
3622cd6
style: apply google-java-format
zeitlinger Jun 8, 2026
deedae3
fix: suppress deprecation warning in MetricWithFixedMetadata
zeitlinger Jun 8, 2026
64044ab
fix: keep internal MetricMetadata builder hooks unstable
zeitlinger Jun 9, 2026
4766529
style: apply google-java-format
zeitlinger Jun 9, 2026
938e4f2
docs: clarify internal MetricMetadata builder hooks
zeitlinger Jun 9, 2026
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17 changes: 16 additions & 1 deletion docs/apidiffs/current_vs_latest/prometheus-metrics-model.txt
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8 changes: 7 additions & 1 deletion ...etrics-core/src/main/java/io/prometheus/metrics/core/metrics/MetricWithFixedMetadata.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,13 @@ protected MetricWithFixedMetadata(Builder<?, ?> builder) {
String originalName = builder.originalName;
String expositionBaseName = makeExpositionBaseName(originalName, builder.unit);
this.metadata =
new MetricMetadata(name, expositionBaseName, originalName, builder.help, builder.unit);
MetricMetadata.builder()
.name(name)
.expositionBaseName(expositionBaseName)
.originalName(originalName)
.help(builder.help)
.unit(builder.unit)
.build();
this.labelNames = Arrays.copyOf(builder.labelNames, builder.labelNames.length);
}

Expand Down
129 changes: 123 additions & 6 deletions ...eus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,111 @@ public MetricMetadata(String name, @Nullable String help, @Nullable Unit unit) {
this(name, name, help, unit);
}

/**
* Creates a builder for {@link MetricMetadata}.
*
* <p>Use the builder instead of the multi-arg constructors for cleaner, more readable code:
*
* <pre>{@code
* MetricMetadata.builder()
* .name("http_requests")
* .help("Total HTTP requests")
* .unit(Unit.BYTES)
* .counterSuffix(true)
* .build();
* }</pre>
*/
@StableApi
public static Builder builder() {
return new Builder();
}

/** Builder for {@link MetricMetadata}. */
public static final class Builder {

@jaydeluca jaydeluca Jun 8, 2026

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will this solve the use cases in this repo that we now have the suppressions on? i'm not sure it allows us to actually fully deprecate the constructors as-is.

For example, for MetricWithFixedMetadata i think we'd need:

    this.metadata = MetricMetadata.builder()
      .name(name)
      .expositionBaseName(expositionBaseName)
      .originalName(originalName)
      .help(builder.help)
      .unit(builder.unit)
      .build();

It might be worth trying to migrate any of the ones where we suppress the deprecation warning, just to see if it's possible

@zeitlinger zeitlinger Jun 9, 2026

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good idea - done

@Nullable private String name;
@Nullable private String expositionBaseName;
@Nullable private String originalName;
@Nullable private String help;
@Nullable private Unit unit;
private boolean counterSuffix;

private Builder() {}

/** Required. The base metric name (without type suffix like {@code _total}). */
@StableApi
public Builder name(String name) {
this.name = name;
if (originalName == null) {
this.originalName = name;
}
return this;
}

/**
* Internal use only. Not part of the stable API.
*
* <p>Allows internal callers to preserve a separate exposition base name.
*/
public Builder expositionBaseName(String expositionBaseName) {
this.expositionBaseName = expositionBaseName;
return this;
}

/**
* Internal use only. Not part of the stable API.
*
* <p>Allows internal callers to preserve the raw name before normalization.
*/
public Builder originalName(String originalName) {
this.originalName = originalName;
return this;
}

/** Optional. Human-readable description of the metric. */
@StableApi
public Builder help(@Nullable String help) {
this.help = help;
return this;
}

/** Optional. The unit of measurement. Appended to the name if not already present. */
@StableApi
public Builder unit(@Nullable Unit unit) {
this.unit = unit;
return this;
}

/**
* Optional. When {@code true}, the writer appends {@code _total} to the exposition name. Use
* this for counter metrics, especially UTF-8 names where the writer cannot infer it from the
* snapshot type alone.
*/
@StableApi
public Builder counterSuffix(boolean counterSuffix) {
this.counterSuffix = counterSuffix;
return this;
}

/** Builds the {@link MetricMetadata}. Throws if {@code name} was not set. */
@StableApi
public MetricMetadata build() {
if (name == null) {
throw new IllegalArgumentException("name is required");
}
String baseName = appendUnitIfMissing(name, unit);
String originalName = this.originalName == null ? name : this.originalName;
String expositionBaseName =
appendUnitIfMissing(
this.expositionBaseName == null ? baseName : this.expositionBaseName, unit);
if (counterSuffix
&& !expositionBaseName.endsWith("_total")
&& !expositionBaseName.endsWith(".total")) {
expositionBaseName = expositionBaseName + "_total";
}
return new MetricMetadata(baseName, expositionBaseName, originalName, help, unit);
}
}

/**
* Constructor with exposition base name.
*
Expand All @@ -82,7 +187,9 @@ public MetricMetadata(String name, @Nullable String help, @Nullable Unit unit) {
* format writers for smart-append logic
* @param help optional. May be {@code null}.
* @param unit optional. May be {@code null}.
* @deprecated Use {@link #builder()} instead.
*/
@Deprecated
public MetricMetadata(
String name, String expositionBaseName, @Nullable String help, @Nullable Unit unit) {
this(name, expositionBaseName, expositionBaseName, help, unit);
Expand All @@ -97,7 +204,9 @@ public MetricMetadata(
* @param originalName the raw name as provided by the user, before any modification
* @param help optional. May be {@code null}.
* @param unit optional. May be {@code null}.
* @deprecated Use {@link #builder()} instead.
*/
@Deprecated
public MetricMetadata(
String name,
String expositionBaseName,
Expand Down Expand Up @@ -174,6 +283,13 @@ public Unit getUnit() {
return unit;
}

private static String appendUnitIfMissing(String name, @Nullable Unit unit) {
if (unit != null && !name.endsWith("_" + unit) && !name.endsWith("." + unit)) {
return name + "_" + unit;
}
return name;
}

private void validate() {
if (name == null) {
throw new IllegalArgumentException("Missing required field: name is null");
Expand Down Expand Up @@ -206,11 +322,12 @@ private void validate() {
}

MetricMetadata escape(EscapingScheme escapingScheme) {
return new MetricMetadata(
PrometheusNaming.escapeName(name, escapingScheme),
PrometheusNaming.escapeName(expositionBaseName, escapingScheme),
PrometheusNaming.escapeName(originalName, escapingScheme),
help,
unit);
return MetricMetadata.builder()
.name(PrometheusNaming.escapeName(name, escapingScheme))
.expositionBaseName(PrometheusNaming.escapeName(expositionBaseName, escapingScheme))
.originalName(PrometheusNaming.escapeName(originalName, escapingScheme))
.help(help)
.unit(unit)
.build();
}
}
13 changes: 7 additions & 6 deletions ...rics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadataSupport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,12 +25,13 @@ private static MetricMetadata typedMetadata(
String suffix,
String dotSuffix) {
String baseName = stripSuffix(originalName, suffix, dotSuffix);
return new MetricMetadata(
appendUnitIfMissing(baseName, unit),
appendUnitIfMissing(originalName, unit),
originalName,
help,
unit);
return MetricMetadata.builder()
.name(appendUnitIfMissing(baseName, unit))
.expositionBaseName(appendUnitIfMissing(originalName, unit))
.originalName(originalName)
.help(help)
.unit(unit)
.build();
}

private static String appendUnitIfMissing(String name, @Nullable Unit unit) {
Expand Down
84 changes: 84 additions & 0 deletions ...metrics-model/src/test/java/io/prometheus/metrics/model/snapshots/MetricMetadataTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ void testUnitNotDuplicated() {
assertThat(sanitizeMetricName("my_counter_bytes", Unit.BYTES)).isEqualTo("my_counter_bytes");
}

@SuppressWarnings("deprecation")
@Test
void testFiveArgConstructor() {
MetricMetadata metadata =
Expand All @@ -94,6 +95,7 @@ void testFiveArgConstructor() {
assertThat(metadata.getUnit()).isEqualTo(Unit.BYTES);
}

@SuppressWarnings("deprecation")
@Test
void testFourArgConstructorDefaultsOriginalName() {
MetricMetadata metadata = new MetricMetadata("req_bytes", "req_bytes", "help", Unit.BYTES);
Expand All @@ -107,4 +109,86 @@ void testThreeArgConstructorDefaultsOriginalName() {
assertThat(metadata.getOriginalName()).isEqualTo("req_bytes");
assertThat(metadata.getExpositionBaseName()).isEqualTo("req_bytes");
}

@Test
void builder_noUnit() {
MetricMetadata m = MetricMetadata.builder().name("requests").help("total requests").build();
assertThat(m.getName()).isEqualTo("requests");
assertThat(m.getExpositionBaseName()).isEqualTo("requests");
assertThat(m.getOriginalName()).isEqualTo("requests");
assertThat(m.getHelp()).isEqualTo("total requests");
assertThat(m.getUnit()).isNull();
}

@Test
void builder_unitAppendedWhenAbsent() {
MetricMetadata m = MetricMetadata.builder().name("requests").unit(Unit.BYTES).build();
assertThat(m.getName()).isEqualTo("requests_bytes");
assertThat(m.getExpositionBaseName()).isEqualTo("requests_bytes");
assertThat(m.getOriginalName()).isEqualTo("requests");
}

@Test
void builder_unitNotDuplicatedWhenPresent() {
MetricMetadata m = MetricMetadata.builder().name("requests_bytes").unit(Unit.BYTES).build();
assertThat(m.getName()).isEqualTo("requests_bytes");
assertThat(m.getExpositionBaseName()).isEqualTo("requests_bytes");
assertThat(m.getOriginalName()).isEqualTo("requests_bytes");
}

@Test
void builder_counterSuffixAppended() {
MetricMetadata m = MetricMetadata.builder().name("requests").counterSuffix(true).build();
assertThat(m.getName()).isEqualTo("requests");
assertThat(m.getExpositionBaseName()).isEqualTo("requests_total");
assertThat(m.getOriginalName()).isEqualTo("requests");
}

@Test
void builder_counterSuffixAndUnit() {
MetricMetadata m =
MetricMetadata.builder().name("requests").unit(Unit.BYTES).counterSuffix(true).build();
assertThat(m.getName()).isEqualTo("requests_bytes");
assertThat(m.getExpositionBaseName()).isEqualTo("requests_bytes_total");
assertThat(m.getOriginalName()).isEqualTo("requests");
}

@Test
void builder_utf8NameWithCounterSuffix() {
MetricMetadata m = MetricMetadata.builder().name("my.requests").counterSuffix(true).build();
assertThat(m.getName()).isEqualTo("my.requests");
assertThat(m.getExpositionBaseName()).isEqualTo("my.requests_total");
assertThat(m.getPrometheusName()).isEqualTo("my_requests");
assertThat(m.getExpositionBasePrometheusName()).isEqualTo("my_requests_total");
}

@Test
void builder_customOriginalAndExpositionBaseName() {
MetricMetadata m =
MetricMetadata.builder()
.name("requests_bytes")
.expositionBaseName("requests_total_bytes")
.originalName("requests_total")
.help("help")
.unit(Unit.BYTES)
.build();
assertThat(m.getName()).isEqualTo("requests_bytes");
assertThat(m.getExpositionBaseName()).isEqualTo("requests_total_bytes");
assertThat(m.getOriginalName()).isEqualTo("requests_total");
assertThat(m.getHelp()).isEqualTo("help");
assertThat(m.getUnit()).isEqualTo(Unit.BYTES);
}

@Test
void builder_nonCounterExpositionBaseEqualsName() {
MetricMetadata m = MetricMetadata.builder().name("active_connections").build();
assertThat(m.getExpositionBaseName()).isEqualTo(m.getName());
}

@Test
void builder_nameRequired() {
assertThatExceptionOfType(IllegalArgumentException.class)
.isThrownBy(() -> MetricMetadata.builder().help("help").build())
.withMessage("name is required");
}
}
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