Hide HttpHeaders.toMultiMap API (Azure#24428)

Author: alzimmermsft

sdk/core/azure-core-http-netty/src/main/java/com/azure/core/http/netty/implementation/NettyToAzureCoreHttpHeadersWrapper.java

@@ -130,8 +130,7 @@ public Map<String, String> toMap() {
         return abstractMap;
     }
 
-    @Override
-    public Map<String, String[]> toMultiMap() {
+    Map<String, String[]> toMultiMap() {
         if (abstractMultiMap == null) {
             abstractMultiMap = new DeferredCacheImmutableMap<>(LOGGER, new HashMap<>(), nettyHeaders,
                 getAll -> getAll.toArray(new String[0]));

sdk/core/azure-core/src/main/java/com/azure/core/http/HttpHeaders.java

@@ -250,7 +250,7 @@ public Map<String, String> toMap() {
      *
      * @return the headers in a copied and unmodifiable form.
      */
-    public Map<String, String[]> toMultiMap() {
+    Map<String, String[]> toMultiMap() {
         final Map<String, String[]> result = new HashMap<>();
         for (final HttpHeader header : headers.values()) {
             result.put(header.getName(), header.getValues());

sdk/core/azure-core/src/main/java/com/azure/core/http/rest/RestProxy.java

@@ -201,10 +201,16 @@ static Flux<ByteBuffer> validateLength(final HttpRequest request) {
      * @return The updated context containing the span context.
      */
     private Context startTracingSpan(Method method, Context context) {
-        boolean disableTracing = (boolean) context.getData(Tracer.DISABLE_TRACING_KEY).orElse(false);
-        if (!TracerProxy.isTracingEnabled() || disableTracing) {
+        // First check if tracing is enabled. This is an optimized operation, so it is done first.
+        if (!TracerProxy.isTracingEnabled()) {
             return context;
         }
+
+        // Then check if this method disabled tracing. This requires walking a linked list, so do it last.
+        if ((boolean) context.getData(Tracer.DISABLE_TRACING_KEY).orElse(false)) {
+            return context;
+        }
+
         String spanName = interfaceParser.getServiceName() + "." + method.getName();
         context = TracerProxy.setSpanName(spanName, context);
         return TracerProxy.start(spanName, context);