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feat: Add logic for handling content negotation flag with OM2 #1986

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63fa420
Add logic for handling content negotation flag with OM2
jaydeluca Mar 30, 2026
7ff14dc
fix lint
jaydeluca Mar 30, 2026
c2b2796
fix: handle multi-type Accept headers in parseOpenMetricsVersion (#1987)
zeitlinger Mar 30, 2026
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35 changes: 33 additions & 2 deletions ...-textformats/src/main/java/io/prometheus/metrics/expositionformats/ExpositionFormats.java
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Original file line number Diff line number Diff line change
Expand Up @@ -63,9 +63,17 @@ public ExpositionFormatWriter findWriter(@Nullable String acceptHeader) {
return prometheusProtobufWriter;
}

// Prefer OM2 over OM1 when any OM2 feature is enabled
if (isOpenMetrics2Enabled() && openMetrics2TextFormatWriter.accepts(acceptHeader)) {
return openMetrics2TextFormatWriter;
if (openMetrics2TextFormatWriter.getOpenMetrics2Properties().getContentNegotiation()) {
String version = parseOpenMetricsVersion(acceptHeader);
if ("2.0.0".equals(version)) {
return openMetrics2TextFormatWriter;
}
// version=1.0.0 or no version: fall through to OM1
} else {
// contentNegotiation=false: OM2 handles all OpenMetrics requests
return openMetrics2TextFormatWriter;
}
}

if (openMetricsTextFormatWriter.accepts(acceptHeader)) {
Expand Down Expand Up @@ -94,4 +102,27 @@ public OpenMetricsTextFormatWriter getOpenMetricsTextFormatWriter() {
public OpenMetrics2TextFormatWriter getOpenMetrics2TextFormatWriter() {
return openMetrics2TextFormatWriter;
}

@Nullable
private static String parseOpenMetricsVersion(@Nullable String acceptHeader) {
if (acceptHeader == null) {
return null;
}
for (String mediaType : acceptHeader.split(",")) {
if (mediaType.contains("application/openmetrics-text")) {
for (String param : mediaType.split(";")) {
String[] tokens = param.split("=");
if (tokens.length == 2) {
String key = tokens[0].trim();
String value = tokens[1].trim();
if (key.equals("version")) {
return value;
}
}
}
return null;
}
}
return null;
}
}
146 changes: 121 additions & 25 deletions ...tformats/src/test/java/io/prometheus/metrics/expositionformats/ExpositionFormatsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -155,7 +155,8 @@ void testOM2EnabledWithFeatureFlags() {
.build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer = formats.findWriter("application/openmetrics-text");
ExpositionFormatWriter writer =
formats.findWriter("application/openmetrics-text; version=2.0.0");
assertThat(writer).isInstanceOf(OpenMetrics2TextFormatWriter.class);
}

Expand All @@ -173,6 +174,94 @@ void testProtobufWriterTakesPrecedence() {
assertThat(writer).isInstanceOf(PrometheusProtobufWriter.class);
}

@Test
void testOM2ContentNegotiationWithVersion2() {
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(true).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer =
formats.findWriter("application/openmetrics-text; version=2.0.0");
assertThat(writer).isInstanceOf(OpenMetrics2TextFormatWriter.class);
}

@Test
void testOM2ContentNegotiationWithVersion1() {
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(true).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer =
formats.findWriter("application/openmetrics-text; version=1.0.0");
assertThat(writer).isInstanceOf(OpenMetricsTextFormatWriter.class);
}

@Test
void testOM2ContentNegotiationWithNoVersion() {
// When contentNegotiation=true and Accept header has no version, use OM1 writer
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(true).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer = formats.findWriter("application/openmetrics-text");
assertThat(writer).isInstanceOf(OpenMetricsTextFormatWriter.class);
}

@Test
void testOM2ContentNegotiationDisabled() {
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(false).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer1 = formats.findWriter("application/openmetrics-text");
ExpositionFormatWriter writer2 =
formats.findWriter("application/openmetrics-text; version=1.0.0");
ExpositionFormatWriter writer3 =
formats.findWriter("application/openmetrics-text; version=2.0.0");
assertThat(writer1).isInstanceOf(OpenMetrics2TextFormatWriter.class);
assertThat(writer2).isInstanceOf(OpenMetrics2TextFormatWriter.class);
assertThat(writer3).isInstanceOf(OpenMetrics2TextFormatWriter.class);
}

@Test
void testOM2ContentNegotiationMultiTypeAcceptHeaderWithoutOMVersion() {
// When the Accept header has multiple media types and only text/plain has a version,
// the openmetrics type should be treated as having no version (use OM1).
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(true).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer =
formats.findWriter("application/openmetrics-text, text/plain; version=0.0.4");
assertThat(writer).isInstanceOf(OpenMetricsTextFormatWriter.class);
}

@Test
void testOM2ContentNegotiationMultiTypeAcceptHeaderWithOMVersion() {
// When the Accept header has multiple media types and openmetrics has version=2.0.0,
// the OM2 writer should be selected.
PrometheusProperties props =
PrometheusProperties.builder()
.openMetrics2Properties(
OpenMetrics2Properties.builder().enabled(true).contentNegotiation(true).build())
.build();
ExpositionFormats formats = ExpositionFormats.init(props);
ExpositionFormatWriter writer =
formats.findWriter(
"application/openmetrics-text; version=2.0.0, text/plain; version=0.0.4");
assertThat(writer).isInstanceOf(OpenMetrics2TextFormatWriter.class);
}

@Test
void testCounterComplete() throws IOException {
String openMetricsText =
Expand Down Expand Up @@ -1977,14 +2066,14 @@ void testClassicGaugeHistogramCountAndSum() throws IOException {
void testClassicHistogramWithDots() throws IOException {
String openMetricsText =
"""
# TYPE U__my_2e_request_2e_duration_2e_seconds histogram
# UNIT U__my_2e_request_2e_duration_2e_seconds seconds
# HELP U__my_2e_request_2e_duration_2e_seconds Request duration in seconds
U__my_2e_request_2e_duration_2e_seconds_bucket{U__http_2e_path="/hello",le="+Inf"} 130 # {U__some_2e_exemplar_2e_key="some value"} 3.0 1690298864.383
U__my_2e_request_2e_duration_2e_seconds_count{U__http_2e_path="/hello"} 130
U__my_2e_request_2e_duration_2e_seconds_sum{U__http_2e_path="/hello"} 0.01
# EOF
""";
# TYPE U__my_2e_request_2e_duration_2e_seconds histogram
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@jaydeluca jaydeluca Mar 30, 2026

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seems like maybe some of the new linting rules didn't like what was previously in this file

# UNIT U__my_2e_request_2e_duration_2e_seconds seconds
# HELP U__my_2e_request_2e_duration_2e_seconds Request duration in seconds
U__my_2e_request_2e_duration_2e_seconds_bucket{U__http_2e_path="/hello",le="+Inf"} 130 # {U__some_2e_exemplar_2e_key="some value"} 3.0 1690298864.383
U__my_2e_request_2e_duration_2e_seconds_count{U__http_2e_path="/hello"} 130
U__my_2e_request_2e_duration_2e_seconds_sum{U__http_2e_path="/hello"} 0.01
# EOF
""";
String openMetricsTextWithExemplarsOnAllTimeSeries =
"# TYPE my_request_duration_seconds histogram\n"
+ "# UNIT my_request_duration_seconds seconds\n"
Expand Down Expand Up @@ -2398,14 +2487,14 @@ void testNativeHistogramMinimal() throws IOException {
void testNativeHistogramWithDots() throws IOException {
String openMetricsText =
"""
# TYPE U__my_2e_request_2e_duration_2e_seconds histogram
# UNIT U__my_2e_request_2e_duration_2e_seconds seconds
# HELP U__my_2e_request_2e_duration_2e_seconds Request duration in seconds
U__my_2e_request_2e_duration_2e_seconds_bucket{U__http_2e_path="/hello",le="+Inf"} 4 # {U__some_2e_exemplar_2e_key="some value"} 3.0 1690298864.383
U__my_2e_request_2e_duration_2e_seconds_count{U__http_2e_path="/hello"} 4
U__my_2e_request_2e_duration_2e_seconds_sum{U__http_2e_path="/hello"} 3.2
# EOF
""";
# TYPE U__my_2e_request_2e_duration_2e_seconds histogram
# UNIT U__my_2e_request_2e_duration_2e_seconds seconds
# HELP U__my_2e_request_2e_duration_2e_seconds Request duration in seconds
U__my_2e_request_2e_duration_2e_seconds_bucket{U__http_2e_path="/hello",le="+Inf"} 4 # {U__some_2e_exemplar_2e_key="some value"} 3.0 1690298864.383
U__my_2e_request_2e_duration_2e_seconds_count{U__http_2e_path="/hello"} 4
U__my_2e_request_2e_duration_2e_seconds_sum{U__http_2e_path="/hello"} 3.2
# EOF
""";
String openMetricsTextWithExemplarsOnAllTimeSeries =
"# TYPE my_request_duration_seconds histogram\n"
+ "# UNIT my_request_duration_seconds seconds\n"
Expand Down Expand Up @@ -2876,12 +2965,19 @@ void testLabelValueEscape() throws IOException {

@ParameterizedTest
@CsvSource({
"'application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited', 'application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited; escaping=underscores'",
"'application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited',"
+ " 'application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily;"
+ " encoding=delimited; escaping=underscores'",
"'text/plain;version=0.0.4', 'text/plain; version=0.0.4; charset=utf-8; escaping=underscores'",
"'application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited; escaping=allow-utf-8', 'application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited; escaping=allow-utf-8'",
"'application/openmetrics-text', 'application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=underscores'",
"'application/openmetrics-text;version=0.0.1; escaping=underscores', 'application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=underscores'",
"'text/plain;version=0.0.4; escaping=allow-utf-8', 'text/plain; version=0.0.4; charset=utf-8; escaping=allow-utf-8'"
"'application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited;"
+ " escaping=allow-utf-8', 'application/vnd.google.protobuf;"
+ " proto=io.prometheus.client.MetricFamily; encoding=delimited; escaping=allow-utf-8'",
"'application/openmetrics-text', 'application/openmetrics-text; version=1.0.0; charset=utf-8;"
+ " escaping=underscores'",
"'application/openmetrics-text;version=0.0.1; escaping=underscores',"
+ " 'application/openmetrics-text; version=1.0.0; charset=utf-8; escaping=underscores'",
"'text/plain;version=0.0.4; escaping=allow-utf-8', 'text/plain; version=0.0.4; charset=utf-8;"
+ " escaping=allow-utf-8'"
})
public void testFindWriter(String acceptHeaderValue, String expectedFmt) {
ExpositionFormats expositionFormats = ExpositionFormats.init();
Expand Down Expand Up @@ -2910,9 +3006,9 @@ void testWrite() throws IOException {

String expected =
"""
# TYPE foo_metric untyped
foo_metric 1.234
""";
# TYPE foo_metric untyped
foo_metric 1.234
""";

assertThat(new String(out, UTF_8)).hasToString(expected);
}
Expand Down
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