Allow error response for worker pool overload to be customized by handler

2 files changed, 14 insertions, 6 deletions

diff --git a/container-core/abi-spec.json b/container-core/abi-spec.json
index 244087e0271..4f0b0f2ff12 100644
--- a/container-core/abi-spec.json
+++ b/container-core/abi-spec.json
@@ -631,7 +631,8 @@
       "protected void <init>(java.util.concurrent.Executor, com.yahoo.jdisc.Metric, boolean)",
       "public final com.yahoo.jdisc.handler.ContentChannel handleRequest(com.yahoo.jdisc.Request, com.yahoo.jdisc.handler.ResponseHandler)",
       "public java.time.Duration getTimeout()",
-      "protected abstract void handleRequest(com.yahoo.jdisc.Request, com.yahoo.jdisc.handler.BufferedContentChannel, com.yahoo.jdisc.handler.ResponseHandler)"
+      "protected abstract void handleRequest(com.yahoo.jdisc.Request, com.yahoo.jdisc.handler.BufferedContentChannel, com.yahoo.jdisc.handler.ResponseHandler)",
+      "protected void writeErrorResponseWhenOverloadedWorkerPool(com.yahoo.jdisc.Request, com.yahoo.jdisc.handler.ResponseHandler)"
     ],
     "fields": [
       "protected final com.yahoo.jdisc.Metric metric"
diff --git a/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedRequestHandler.java b/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedRequestHandler.java
index c198e0e8b32..0e8865538ee 100644
--- a/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedRequestHandler.java
+++ b/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedRequestHandler.java
@@ -16,13 +16,11 @@ import com.yahoo.jdisc.handler.ReadableContentChannel;
 import com.yahoo.jdisc.handler.ResponseDispatch;
 import com.yahoo.jdisc.handler.ResponseHandler;
 
-import java.util.Objects;
-import java.util.logging.Level;
-
 import java.net.URI;
 import java.time.Duration;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.Executor;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeUnit;
@@ -163,6 +161,14 @@ public abstract class ThreadedRequestHandler extends AbstractRequestHandler {
     protected abstract void handleRequest(Request request, BufferedContentChannel requestContent,
                                           ResponseHandler responseHandler);
 
+    /**
+     * Invoked to write an error response when the worker pool is overloaded.
+     * A subclass may override this method to define a custom response.
+     */
+    protected void writeErrorResponseOnOverload(Request request, ResponseHandler responseHandler) {
+        ResponseDispatch.newInstance(Response.Status.SERVICE_UNAVAILABLE).dispatch(responseHandler);
+    }
+
     private class RequestTask implements ResponseHandler, Runnable {
 
         final Request request;
@@ -237,14 +243,15 @@ public abstract class ThreadedRequestHandler extends AbstractRequestHandler {
             }
         }
 
+
         /**
          * Clean up when the task can not be executed because no worker thread is available.
          */
-        public void failOnOverload() {
+        void failOnOverload() {
             try (ResourceReference reference = requestReference) {
                 incrementRejectedRequests();
                 logRejectedRequests();
-                ResponseDispatch.newInstance(Response.Status.SERVICE_UNAVAILABLE).dispatch(responseHandler);
+                writeErrorResponseOnOverload(request, responseHandler);
             }
         }
     }