Own Prometheus name translation

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/Otel2PrometheusConverter.java

@@ -5,7 +5,6 @@
 
 package io.opentelemetry.exporter.prometheus;
 
-import static io.prometheus.metrics.model.snapshots.PrometheusNaming.prometheusName;
 import static java.util.Objects.requireNonNull;
 
 import io.opentelemetry.api.common.AttributeKey;
@@ -624,6 +623,32 @@ private static boolean containsOnlyUnderscores(String value) {
     return true;
   }
 
+  private static String convertLegacyMetricName(String name) {
+    if (name.isEmpty()) {
+      return name;
+    }
+
+    StringBuilder result = new StringBuilder(name.length());
+    for (int i = 0; i < name.length(); ) {
+      int codePoint = name.codePointAt(i);
+      if (isValidLegacyMetricChar(codePoint, i)) {
+        result.appendCodePoint(codePoint);
+      } else {
+        result.append('_');
+      }
+      i += Character.charCount(codePoint);
+    }
+    return result.toString();
+  }
+
+  private static boolean isValidLegacyMetricChar(int codePoint, int index) {
+    return (codePoint >= 'a' && codePoint <= 'z')
+        || (codePoint >= 'A' && codePoint <= 'Z')
+        || codePoint == '_'
+        || codePoint == ':'
+        || (codePoint >= '0' && codePoint <= '9' && index > 0);
+  }
+
   private MetricMetadata convertMetadata(MetricData metricData, boolean isCounter) {
     switch (translationStrategy) {
       case UNDERSCORE_ESCAPING_WITH_SUFFIXES:
@@ -639,7 +664,7 @@ private MetricMetadata convertMetadata(MetricData metricData, boolean isCounter)
   }
 
   private static MetricMetadata convertMetadataEscapedWithSuffixes(MetricData metricData) {
-    String name = prometheusName(metricData.getName());
+    String name = convertLegacyMetricName(metricData.getName());
     String help = metricData.getDescription();
     Unit unit = PrometheusUnitsHelper.convertUnit(metricData.getUnit());
     name = stripRepeatedUnderscores(stripReservedMetricSuffixes(name));
@@ -650,7 +675,7 @@ private static MetricMetadata convertMetadataEscapedWithSuffixes(MetricData metr
   }
 
   private static MetricMetadata convertMetadataEscapedWithoutSuffixes(MetricData metricData) {
-    String rawName = stripRepeatedUnderscores(prometheusName(metricData.getName()));
+    String rawName = stripRepeatedUnderscores(convertLegacyMetricName(metricData.getName()));
     String name = stripReservedMetricSuffixes(rawName);
     return new MetricMetadata(name, rawName, rawName, metricData.getDescription(), null);
   }

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/PrometheusUnitsHelper.java

@@ -5,7 +5,6 @@
 
 package io.opentelemetry.exporter.prometheus;
 
-import io.prometheus.metrics.model.snapshots.PrometheusNaming;
 import io.prometheus.metrics.model.snapshots.Unit;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -99,7 +98,7 @@ static Unit convertUnit(String otelUnit) {
   @Nullable
   private static Unit unitOrNull(String name) {
     try {
-      String sanitized = PrometheusNaming.sanitizeUnitName(name);
+      String sanitized = sanitizeUnitName(name);
       sanitized = stripReservedUnitSuffixes(sanitized);
       if (sanitized.isEmpty()) {
         return null;
@@ -110,6 +109,42 @@ private static Unit unitOrNull(String name) {
     }
   }
 
+  private static String sanitizeUnitName(String unitName) {
+    if (unitName.isEmpty()) {
+      throw new IllegalArgumentException("Cannot convert an empty string to a valid unit name.");
+    }
+    String sanitizedName = replaceIllegalCharsInUnitName(unitName);
+    while (sanitizedName.startsWith("_") || sanitizedName.startsWith(".")) {
+      sanitizedName = sanitizedName.substring(1);
+    }
+    while (sanitizedName.endsWith(".") || sanitizedName.endsWith("_")) {
+      sanitizedName = sanitizedName.substring(0, sanitizedName.length() - 1);
+    }
+    if (sanitizedName.isEmpty()) {
+      throw new IllegalArgumentException(
+          "Cannot convert '" + unitName + "' into a valid unit name.");
+    }
+    return sanitizedName;
+  }
+
+  private static String replaceIllegalCharsInUnitName(String name) {
+    int length = name.length();
+    char[] sanitized = new char[length];
+    for (int i = 0; i < length; i++) {
+      char ch = name.charAt(i);
+      if (ch == ':'
+          || ch == '.'
+          || (ch >= 'a' && ch <= 'z')
+          || (ch >= 'A' && ch <= 'Z')
+          || (ch >= '0' && ch <= '9')) {
+        sanitized[i] = ch;
+      } else {
+        sanitized[i] = '_';
+      }
+    }
+    return new String(sanitized);
+  }
+
   private static String stripReservedUnitSuffixes(String name) {
     boolean modified = true;
     while (modified) {

exporters/prometheus/src/test/java/io/opentelemetry/exporter/prometheus/Otel2PrometheusConverterTest.java

@@ -421,7 +421,7 @@ private static Stream<Arguments> resourceAttributesAdditionArgs() {
   }
 
   @Test
-  void prometheusNameCollisionTest_Issue6277() {
+  void metricNameCollisionTest_Issue6277() {
     // NOTE: Metrics with the same resolved prometheus name should merge. However,
     // Otel2PrometheusConverter is not responsible for merging individual series, so the merge will
     // fail if the two different metrics contain overlapping series. Users should deal with this by