cache discovered jar path

Author: zeitlinger

Diff for: instrumentation/resources/library/src/main/java/io/opentelemetry/instrumentation/resources/JarFileDetector.java

@@ -51,11 +51,15 @@ public JarFileDetector() {
 
   @Nullable
   Path getJarPath() {
-    Path jarPath = getJarPathFromProcessHandle();
-    if (jarPath != null) {
-      return jarPath;
-    }
-    return getJarPathFromSunCommandLine();
+    return ResourceDiscoveryCache.get(
+        "jarPath",
+        () -> {
+          Path jarPath = getJarPathFromProcessHandle();
+          if (jarPath != null) {
+            return jarPath;
+          }
+          return getJarPathFromSunCommandLine();
+        });
   }
 
   Optional<Manifest> getManifestFromJarFile() {

Diff for: instrumentation/resources/library/src/main/java/io/opentelemetry/instrumentation/resources/ResourceDiscoveryCache.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.resources;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Supplier;
+
+public class ResourceDiscoveryCache {
+  private static final ConcurrentHashMap<String, Object> cache = new ConcurrentHashMap<>();
+
+  private ResourceDiscoveryCache() {}
+
+  // visible for testing
+  public static void resetForTest() {
+    cache.clear();
+  }
+
+  @SuppressWarnings("unchecked")
+  public static <T> T get(String key, Supplier<T> supplier) {
+    return (T) cache.computeIfAbsent(key, k -> supplier.get());
+  }
+}

Diff for: instrumentation/resources/library/src/test/java/io/opentelemetry/instrumentation/resources/JarServiceNameDetectorTest.java

@@ -17,6 +17,7 @@
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.extension.ExtensionContext;
@@ -33,6 +34,11 @@ class JarServiceNameDetectorTest {
 
   @Mock ConfigProperties config;
 
+  @BeforeEach
+  void setUp() {
+    ResourceDiscoveryCache.resetForTest();
+  }
+
   @Test
   void createResource_empty() {
     String[] processArgs = new String[0];

Diff for: instrumentation/resources/library/src/test/java/io/opentelemetry/instrumentation/resources/ManifestResourceProviderTest.java

@@ -19,11 +19,17 @@
 import java.util.jar.Manifest;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.TestFactory;
 
 class ManifestResourceProviderTest {
 
+  @BeforeEach
+  void setUp() {
+    ResourceDiscoveryCache.resetForTest();
+  }
+
   private static class TestCase {
     private final String name;
     private final String expectedName;