normalize system props before lookup to avoid ambiguity of "experimental-foo" and "experimental.foo" that both translate to "foo/development"

Author: zeitlinger

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/internal/ConfigPropertiesUtil.java

@@ -12,12 +12,14 @@
 import io.opentelemetry.api.incubator.ExtendedOpenTelemetry;
 import io.opentelemetry.api.incubator.config.ConfigProvider;
 import io.opentelemetry.api.incubator.config.DeclarativeConfigProperties;
-import io.opentelemetry.api.internal.ConfigUtil;
 import java.util.Arrays;
+import java.util.ConcurrentModificationException;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Properties;
 import java.util.stream.Collectors;
 import javax.annotation.Nullable;
 
@@ -35,11 +37,11 @@ public static Map<String, String> load() {
     Map<String, String> config = new HashMap<>();
     System.getenv()
         .forEach(
-            (name, value) -> config.put(ConfigUtil.normalizeEnvironmentVariableKey(name), value));
-    ConfigUtil.safeSystemProperties()
+            (name, value) -> config.put(normalizeEnvironmentVariableKey(name), value));
+    safeSystemProperties()
         .forEach(
             (key, value) ->
-                config.put(ConfigUtil.normalizePropertyKey(key.toString()), value.toString()));
+                config.put(normalizePropertyKey(key.toString()), value.toString()));
     return config;
   }
 
@@ -113,7 +115,7 @@ public static int getInt(String propertyName, int defaultValue) {
    */
   @Nullable
   public static String getString(String propertyName) {
-    return config.get(ConfigUtil.normalizePropertyKey(propertyName));
+    return config.get(normalizePropertyKey(propertyName));
   }
 
   /**
@@ -194,5 +196,28 @@ public static String toSystemProperty(String[] propertyName) {
     return "otel.instrumentation." + String.join(".", propertyName).replace('_', '-');
   }
 
+  /**
+   * Normalize an environment variable key by converting to lower case and replacing "_" with ".".
+   */
+  public static String normalizeEnvironmentVariableKey(String key) {
+    return key.toLowerCase(Locale.ROOT).replace("_", ".");
+  }
+
+  /** Normalize a property key by converting to lower case and replacing "-" with ".". */
+  public static String normalizePropertyKey(String key) {
+    return key.toLowerCase(Locale.ROOT).replace("-", ".");
+  }
+
+  /**
+   * Returns a copy of system properties which is safe to iterate over.
+   *
+   * <p>In java 8 and android environments, iterating through system properties may trigger {@link
+   * ConcurrentModificationException}. This method ensures callers can iterate safely without risk
+   * of exception. See https://github.com/open-telemetry/opentelemetry-java/issues/6732 for details.
+   */
+  public static Properties safeSystemProperties() {
+    return (Properties) System.getProperties().clone();
+  }
+
   private ConfigPropertiesUtil() {}
 }