From 172cc6872c2c696abe7ed43dfb93d4c43df8fd4c Mon Sep 17 00:00:00 2001
From: milanmajchrak <milan.majchrak@dataquest.sk>
Date: Fri, 13 Mar 2026 16:30:41 +0100
Subject: [PATCH] Reduce warn logs noise (#1268) + line length fix (#1274)

---
 .../DSpaceApiExceptionControllerAdvice.java   | 27 ++++++++++++++++---
 dspace/config/log4j2.xml                      |  7 +++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
index d18fc860f64b..a02090200ddb 100644
--- a/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
+++ b/dspace-server-webapp/src/main/java/org/dspace/app/rest/exception/DSpaceApiExceptionControllerAdvice.java
@@ -61,6 +61,14 @@
 public class DSpaceApiExceptionControllerAdvice extends ResponseEntityExceptionHandler {
     private static final Logger log = LogManager.getLogger();
 
+    /**
+     * Dedicated logger for 404 NOT_FOUND responses. Configured at OFF level by default
+     * so that expected 404s don't flood production logs.
+     * Set to WARN in log4j2.xml to see 404 responses in logs.
+     */
+    private static final Logger notFoundLog =
+            LogManager.getLogger("org.dspace.app.rest.exception.DSpaceApiExceptionControllerAdvice.NotFound");
+
     /**
      * Default collection of HTTP error codes to log as ERROR with full stack trace.
      */
@@ -300,12 +308,25 @@ private void sendErrorResponse(final HttpServletRequest request,
                 StackTraceElement[] trace = ex.getStackTrace();
                 location = trace.length <= 0 ? "unknown" : trace[0].toString();
             }
-            log.warn("{} (status:{} exception: {} at: {})", message, statusCode,
-                    exceptionMessage, location);
-        }
+            logClientError(statusCode, message,
 
         //Exception properties will be set by org.springframework.boot.web.support.ErrorPageFilter
         response.sendError(statusCode, message);
     }
 
 }
+    /**
+     * Log a 4xx client error. 404 NOT_FOUND is sent to a dedicated logger ({@link #notFoundLog})
+     * at WARN level, but the logger is set to OFF by default in log4j2.xml (suppressed).
+     * Set logger to WARN in log4j2.xml to see 404 responses in logs.
+     */
+    private void logClientError(int statusCode, String message, String exceptionMessage, String location) {
+        if (statusCode == HttpServletResponse.SC_NOT_FOUND) {
+            notFoundLog.warn("{} (status:{} exception: {} at: {})", message, statusCode,
+                    exceptionMessage, location);
+        } else {
+            log.warn("{} (status:{} exception: {} at: {})", message, statusCode,
+                    exceptionMessage, location);
+        }
+    }
+
diff --git a/dspace/config/log4j2.xml b/dspace/config/log4j2.xml
index 2b72fbe1c574..b15085af6e65 100644
--- a/dspace/config/log4j2.xml
+++ b/dspace/config/log4j2.xml
@@ -66,6 +66,13 @@
             <AppenderRef ref='A2'/>
         </Logger>
 
+        <!-- NotFound logger for 404 responses - set to WARN to enable 404 logging -->
+        <Logger name='org.dspace.app.rest.exception.DSpaceApiExceptionControllerAdvice.NotFound'
+                level='OFF'
+                additivity='false'>
+            <AppenderRef ref='A1'/>
+        </Logger>
+
         <!-- Block services logging except on exceptions -->
         <Logger name='org.dspace.kernel'
                 level='ERROR'/>