Stop converting unit "1" to "ratio" in Prometheus exporter

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

@@ -53,7 +53,6 @@ class PrometheusUnitsHelper {
     initUnit("Cel", "celsius");
     initUnit("Hz", "hertz");
     initUnit("%", "percent");
-    initUnit("1", "ratio");
   }
 
   private PrometheusUnitsHelper() {}
@@ -70,12 +69,12 @@ private static void initUnit(String otelName, String pluralName, String singular
 
   @Nullable
   static Unit convertUnit(String otelUnit) {
-    if (otelUnit.isEmpty()) {
+    if (otelUnit.isEmpty() || otelUnit.equals("1")) {
       return null;
     }
     if (otelUnit.contains("{")) {
       otelUnit = otelUnit.replaceAll("\\{[^}]*}", "").trim();
-      if (otelUnit.isEmpty() || otelUnit.equals("/")) {
+      if (otelUnit.isEmpty() || otelUnit.equals("/") || otelUnit.equals("1")) {
         return null;
       }
     }

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

@@ -100,24 +100,24 @@ void metricMetadata(
 
   private static Stream<Arguments> metricMetadataArgs() {
     return Stream.of(
-        // the unity unit "1" is translated to "ratio"
+        // the unity unit "1" is unitless - no suffix added
         Arguments.of(
             createSampleMetricData("sample", "1", MetricDataType.LONG_GAUGE),
-            "sample_ratio gauge",
-            "sample_ratio description",
-            "sample_ratio"),
+            "sample gauge",
+            "sample description",
+            "sample"),
         // unit is appended to metric name
         Arguments.of(
             createSampleMetricData("sample", "unit", MetricDataType.LONG_GAUGE),
             "sample_unit gauge",
             "sample_unit description",
             "sample_unit"),
-        // units in curly braces are dropped
+        // units in curly braces are dropped, "1" is unitless
         Arguments.of(
             createSampleMetricData("sample", "1{dropped}", MetricDataType.LONG_GAUGE),
-            "sample_ratio gauge",
-            "sample_ratio description",
-            "sample_ratio"),
+            "sample gauge",
+            "sample description",
+            "sample"),
         // monotonic sums always include _total suffix
         Arguments.of(
             createSampleMetricData("sample", "unit", MetricDataType.LONG_SUM),
@@ -126,9 +126,9 @@ private static Stream<Arguments> metricMetadataArgs() {
             "sample_unit_total"),
         Arguments.of(
             createSampleMetricData("sample", "1", MetricDataType.LONG_SUM),
-            "sample_ratio_total counter",
-            "sample_ratio_total description",
-            "sample_ratio_total"),
+            "sample_total counter",
+            "sample_total description",
+            "sample_total"),
         // units expressed as numbers other than 1 are retained
         Arguments.of(
             createSampleMetricData("sample", "2", MetricDataType.LONG_SUM),

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

@@ -69,8 +69,8 @@ private static Stream<Arguments> providePrometheusOTelUnitEquivalentPairs() {
         Arguments.of("Cel", "celsius"),
         // Unit not found - Case sensitive
         Arguments.of("S", "S"),
-        // Special case - 1
-        Arguments.of("1", "ratio"),
+        // Special case - 1 is unitless
+        Arguments.of("1", null),
         // Special Case - Drop metric units in {}
         Arguments.of("{packets}", null),
         // Special Case - Dropped metric units only in {}