Issue #14403 - Defer FCGI application dispatch until the parser returns

jetty-core/jetty-fcgi/jetty-fcgi-server/src/main/java/org/eclipse/jetty/fcgi/server/internal/HttpStreamOverFCGI.java

@@ -103,17 +103,15 @@ else if (FCGI.Headers.HTTPS.equalsIgnoreCase(name))
             processField(field);
     }
 
-    public void onHeaders()
+    public Runnable onHeaders()
     {
         String pathQuery = URIUtil.addPathQuery(_path, _query);
         HttpScheme scheme = StringUtil.isEmpty(_secure) ? HttpScheme.HTTP : HttpScheme.HTTPS;
         MetaData.Request request = new MetaData.Request(_connection.getBeginNanoTime(), _method, scheme.asString(), hostPort, pathQuery, HttpVersion.fromString(_version), _headers, -1);
         Runnable task = _httpChannel.onRequest(request);
         _allHeaders.forEach(field -> _httpChannel.getRequest().setAttribute(field.getName(), field.getValue()));
-        // TODO: here we just execute the task.
-        //  However, we should really return all the way back to onFillable()
-        //  and feed the Runnable to an ExecutionStrategy.
-        execute(task);
+        // Return the task to dispatch it after ServerParser.parse() has returned.
+        return task;
     }
 
     private void processField(HttpField field)
@@ -358,11 +356,6 @@ public boolean onIdleTimeout(TimeoutException timeout)
         return !handlingRequest;
     }
 
-    private void execute(Runnable task)
-    {
-        _connection.getConnector().getExecutor().execute(task);
-    }
-
     private class DemandCallback implements Callback
     {
         @Override

jetty-core/jetty-fcgi/jetty-fcgi-server/src/main/java/org/eclipse/jetty/fcgi/server/internal/ServerFCGIConnection.java

@@ -15,6 +15,7 @@
 
 import java.nio.ByteBuffer;
 import java.util.Set;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeoutException;
 
 import org.eclipse.jetty.fcgi.FCGI;
@@ -59,6 +60,7 @@ public class ServerFCGIConnection extends AbstractMetaDataConnection implements
     private boolean useOutputDirectByteBuffers;
     private RetainableByteBuffer inputBuffer;
     private HttpStreamOverFCGI stream;
+    private Runnable onRequest;
 
     public ServerFCGIConnection(Connector connector, EndPoint endPoint, HttpConfiguration configuration, boolean sendStatus200)
     {
@@ -191,7 +193,7 @@ public void onFillable()
                     {
                         if (stream == null && inputBuffer.isEmpty())
                             releaseInputBuffer();
-                        return;
+                        break;
                     }
                 }
                 else if (read == 0)
@@ -207,6 +209,24 @@ else if (read == 0)
                     return;
                 }
             }
+
+            // Dispatch only after the parser has returned and input buffer bookkeeping is complete.
+            Runnable task = onRequest;
+            onRequest = null;
+            if (task != null)
+            {
+                try
+                {
+                    getExecutor().execute(task);
+                }
+                catch (RejectedExecutionException x)
+                {
+                    HttpStreamOverFCGI stream = this.stream;
+                    Runnable failureTask = stream.getHttpChannel().onFailure(x);
+                    this.stream = null;
+                    ThreadPool.executeImmediately(getExecutor(), failureTask);
+                }
+            }
         }
         catch (Exception x)
         {
@@ -359,9 +379,8 @@ public boolean onHeaders(int request)
                 LOG.debug("Request {} headers on {}", request, stream);
             if (stream != null)
             {
-                stream.onHeaders();
-                // We have dispatched to the application,
-                // so we must stop the fill & parse loop.
+                onRequest = stream.onHeaders();
+                // Return to onFillable() before dispatching to the application.
                 return true;
             }
             return false;