♻️ refactor HypertraceConfig to use thread-safe AgentConfigSupplier

Author: ryandens

javaagent-core/src/main/java/org/hypertrace/agent/core/config/HypertraceConfig.java

@@ -51,7 +51,8 @@ private HypertraceConfig() {}
   // so avoiding for perf reasons
   private static volatile boolean servletCausingException;
 
-  private static AgentConfig agentConfig;
+  private static final AgentConfigSupplier agentConfigSupplier =
+      new AgentConfigSupplier(HypertraceConfig::load);
 
   static final String DEFAULT_SERVICE_NAME = "unknown";
   static final String DEFAULT_REPORTING_ENDPOINT = "http://localhost:9411/api/v2/spans";
@@ -61,21 +62,7 @@ private HypertraceConfig() {}
   static final int DEFAULT_BODY_MAX_SIZE_BYTES = 128 * 1024;
 
   public static AgentConfig get() {
-    if (agentConfig == null) {
-      synchronized (HypertraceConfig.class) {
-        if (agentConfig == null) {
-          try {
-            agentConfig = load();
-            log.info(
-                "Config loaded: {}",
-                JsonFormat.printer().omittingInsignificantWhitespace().print(agentConfig));
-          } catch (IOException e) {
-            throw new RuntimeException("Could not load config", e);
-          }
-        }
-      }
-    }
-    return agentConfig;
+    return agentConfigSupplier.get();
   }
 
   public static boolean isInstrumentationEnabled(String primaryName, String[] otherNames) {
@@ -123,16 +110,20 @@ private static boolean isHypertraceType(String message) {
   /** Reset the config, use only in tests. */
   @VisibleForTesting
   public static void reset() {
-    agentConfig = null;
+    agentConfigSupplier.reset();
   }
 
-  private static AgentConfig load() throws IOException {
+  private static AgentConfig load() {
     String configFile = EnvironmentConfig.getProperty(EnvironmentConfig.CONFIG_FILE_PROPERTY);
     if (configFile == null) {
       return EnvironmentConfig.applyPropertiesAndEnvVars(applyDefaults(AgentConfig.newBuilder()))
           .build();
     }
-    return load(configFile);
+    try {
+      return load(configFile);
+    } catch (IOException e) {
+      throw new RuntimeException("Could not load config", e);
+    }
   }
 
   @VisibleForTesting