12.0.x: warn the first time the TCCL fails to be set (#13842)

warn the first time the TCCL fails to be set

Signed-off-by: Ludovic Orban <[email protected]>

Author: lorban

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/handler/ContextHandler.java

@@ -28,6 +28,7 @@
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
@@ -133,6 +134,7 @@ public static ContextHandler getContextHandler(Request request)
     private final MimeTypes.Wrapper _mimeTypes = new MimeTypes.Wrapper();
     private final List<ContextScopeListener> _contextListeners = new CopyOnWriteArrayList<>();
     private final List<VHost> _vhosts = new ArrayList<>();
+    private final AtomicBoolean _enterScopeSetClassloaderFailed = new AtomicBoolean();
 
     private String _displayName;
     private String _contextPath = "/";
@@ -634,8 +636,12 @@ protected ClassLoader enterScope(Request contextRequest)
             }
             catch (Throwable x)
             {
-                if (LOG.isDebugEnabled())
-                    LOG.debug("error setting a context classloader on thread {}", Thread.currentThread(), x);
+                // Log as warning the first time it happens.
+                String msg = "Error setting a context classloader on thread {}";
+                if (_enterScopeSetClassloaderFailed.compareAndSet(false, true))
+                    LOG.warn(msg, Thread.currentThread(), x);
+                else if (LOG.isDebugEnabled())
+                    LOG.debug(msg, Thread.currentThread(), x);
             }
         }
         notifyEnterScope(contextRequest);

jetty-core/jetty-server/src/test/java/org/eclipse/jetty/server/handler/ContextHandlerTest.java

@@ -193,7 +193,8 @@ public boolean handle(Request request, Response response, Callback callback) thr
                     @Override
                     public void run()
                     {
-                        try (Blocker.Callback cb = Blocker.callback())
+                        try (StacklessLogging ignore = new StacklessLogging(ContextHandler.class);
+                             Blocker.Callback cb = Blocker.callback())
                         {
                             // When a classloader is configured, Response.write() tries to set it as the context classloader.
                             response.write(true, ByteBuffer.allocate(32), cb);
@@ -209,6 +210,12 @@ public void run()
                         }
                     }
 
+                    @Override
+                    public ClassLoader getContextClassLoader()
+                    {
+                        return null;
+                    }
+
                     @Override
                     public void setContextClassLoader(ClassLoader cl)
                     {
@@ -258,7 +265,8 @@ public boolean handle(Request request, Response response, Callback callback) thr
                         @Override
                         public void completed(Integer result, Object attachment)
                         {
-                            try (Blocker.Callback cb = Blocker.callback())
+                            try (StacklessLogging ignore = new StacklessLogging(ContextHandler.class);
+                                 Blocker.Callback cb = Blocker.callback())
                             {
                                 // When a classloader is configured, Response.write() tries to set it as the context classloader.
                                 response.write(true, ByteBuffer.allocate(32), cb);