Log exceptions thrown by HttpHandlers in repository integration tests (elastic#48991)

This commit changes the ESMockAPIBasedRepositoryIntegTestCase so 
that HttpHandler are now wrapped in order to log any exceptions that 
could be thrown when executing the server side logic in repository 
integration tests.

Author: tlrx

test/framework/src/main/java/org/elasticsearch/repositories/blobstore/ESMockAPIBasedRepositoryIntegTestCase.java

@@ -22,6 +22,8 @@
 import com.sun.net.httpserver.HttpHandler;
 import com.sun.net.httpserver.HttpServer;
 import org.apache.http.HttpStatus;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.message.ParameterizedMessage;
 import org.elasticsearch.action.admin.indices.forcemerge.ForceMergeResponse;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.common.Strings;
@@ -67,13 +69,7 @@ public static void startHttpServer() throws Exception {
     @Before
     public void setUpHttpServer() {
         handlers = createHttpHandlers();
-        handlers.forEach((c, h) -> {
-            HttpHandler handler = h;
-            if (randomBoolean()) {
-                handler = createErroneousHttpHandler(handler);
-            }
-            httpServer.createContext(c, handler);
-        });
+        handlers.forEach((c, h) -> httpServer.createContext(c, wrap(randomBoolean() ? createErroneousHttpHandler(h) : h, logger)));
     }
 
     @AfterClass
@@ -188,4 +184,19 @@ protected boolean canFailRequest(final HttpExchange exchange) {
             return true;
         }
     }
+
+    /**
+     * Wrap a {@link HttpHandler} to log any thrown exception using the given {@link Logger}.
+     */
+    private static HttpHandler wrap(final HttpHandler handler, final Logger logger) {
+        return exchange -> {
+            try {
+                handler.handle(exchange);
+            } catch (final Exception e) {
+                logger.error(() -> new ParameterizedMessage("Exception when handling request {} {} {}",
+                    exchange.getRemoteAddress(), exchange.getRequestMethod(), exchange.getRequestURI()), e);
+                throw e;
+            }
+        };
+    }
 }