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

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Merged
zeitlinger merged 7 commits into from
Jun 10, 2026
Merged

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
0d7e8a9
fix: narrow stable MetricMetadata api annotations
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 numberDiff line numberDiff 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
143 changes: 136 additions & 7 deletions ...eus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java
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Original file line numberDiff line numberDiff line change
Expand Up@@ -5,7 +5,6 @@
import javax.annotation.Nullable;

/** Immutable container for metric metadata: name, help, unit. */
@StableApi
public final class MetricMetadata {

/**
Expand DownExpand Up@@ -51,11 +50,13 @@ public final class MetricMetadata {
@Nullable private final Unit unit;

/** See {@link #MetricMetadata(String, String, Unit)} */
@StableApi
public MetricMetadata(String name) {
this(name, null, null);
}

/** See {@link #MetricMetadata(String, String, Unit)} */
@StableApi
public MetricMetadata(String name, String help) {
this(name, help, null);
}
Expand All@@ -69,10 +70,116 @@ public MetricMetadata(String name, String help) {
* @param help optional. May be {@code null}.
* @param unit optional. May be {@code null}.
*/
@StableApi
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 {

@jaydelucajaydelucaJun 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

@zeitlingerzeitlingerJun 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 +189,10 @@ 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.
*/
@StableApi
@Deprecated
public MetricMetadata(
String name, String expositionBaseName, @Nullable String help, @Nullable Unit unit) {
this(name, expositionBaseName, expositionBaseName, help, unit);
Expand All@@ -97,7 +207,10 @@ 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.
*/
@StableApi
@Deprecated
public MetricMetadata(
String name,
String expositionBaseName,
Expand All@@ -121,6 +234,7 @@ public MetricMetadata(
* <p>The name may contain any Unicode chars. Use {@link #getPrometheusName()} to get the name in
* legacy Prometheus format, i.e. with all dots and all invalid chars replaced by underscores.
*/
@StableApi
public String getName() {
return name;
}
Expand All@@ -130,6 +244,7 @@ public String getName() {
*
* <p>This is used by Prometheus exposition formats.
*/
@StableApi
public String getPrometheusName() {
return prometheusName;
}
Expand All@@ -139,6 +254,7 @@ public String getPrometheusName() {
* called {@code Counter.builder().name("req").unit(BYTES)}, this returns "req" while {@link
* #getName()} returns "req_bytes" and {@link #getExpositionBaseName()} returns "req_bytes".
*/
@StableApi
public String getOriginalName() {
return originalName;
}
Expand All@@ -148,6 +264,7 @@ public String getOriginalName() {
* if the user called {@code Counter.builder().name("events_total")}, this returns "events_total"
* while {@link #getName()} returns "events".
*/
@StableApi
public String getExpositionBaseName() {
return expositionBaseName;
}
Expand All@@ -156,24 +273,35 @@ public String getExpositionBaseName() {
* Same as {@link #getExpositionBaseName()} but with all invalid characters and dots replaced by
* underscores.
*/
@StableApi
public String getExpositionBasePrometheusName() {
return expositionBasePrometheusName;
}

@StableApi
@Nullable
public String getHelp() {
return help;
}

@StableApi
public boolean hasUnit() {
return unit != null;
}

@StableApi
@Nullable
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 DownExpand Up@@ -206,11 +334,12 @@ 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 numberDiff line numberDiff 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
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