NHSDigital · ORybak5 · May 5, 2026 · May 5, 2026
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * The GP2GP Adaptor will no longer incorrectly fail schema validation.
 * The GP2GP Adaptor now sources the references correctly from within the service code rather than fetching them from the test folder.
 
+### Changed
+* Updated logging configuration to route application logs through async appender settings for improved runtime logging performance.
+
 ## [3.0.0] - 2025-11-06
 
 ### Added

@@ -101,7 +101,7 @@ private static ExchangeFilterFunction errorHandling(RequestType requestType, Htt
 
             var statusCode = clientResponse.statusCode();
             if (statusCode.equals(httpStatus)) {
-                LOGGER.info(requestType + " request successful status_code: {}", statusCode.value());
+                LOGGER.info("{} request successful status_code: {}", requestType, statusCode.value());
                 return Mono.just(clientResponse);
             }
             if (statusCode.is5xxServerError()) {

@@ -57,7 +57,7 @@ public void execute(SendDocumentTaskDefinition taskDefinition) {
         }
 
         var binary = outboundMessage.getAttachments().get(0).getPayload();
-        LOGGER.debug("Attachment size=" + getBytesLengthOfString(binary) + " content-type=" + taskDefinition.getDocumentContentType());
+        LOGGER.debug("Attachment size={} content-type={}", getBytesLengthOfString(binary), taskDefinition.getDocumentContentType());
         if (isLargeAttachment(binary)) {
             outboundMessage.getAttachments().clear(); // since it's a large message, chunks will be sent as external attachments
             outboundMessage.setExternalAttachments(new ArrayList<>());

@@ -115,7 +115,7 @@ public void testForValidReferences(Condition condition) {
             try {
                 messageContext.getInputBundleHolder().getResource(idType);
             } catch (Exception e) {
-                LOGGER.warn("Bundle mapping aborted. Reason: " + e.getMessage());
+                LOGGER.warn("Bundle mapping aborted. Reason: {}", e.getMessage());
                 throw e;
             }
         }

@@ -130,7 +130,7 @@ public void handleContinue(String conversationId, String payload) {
             ehrExtractStatusService.updateEhrExtractStatusContinue(conversationId)
                 .ifPresent(ehrExtractStatus -> {
                     var documents = ehrExtractStatus.getGpcAccessDocument().getDocuments();
-                    LOGGER.info("Sending documents for: ConversationId: " + conversationId);
+                    LOGGER.info("Sending documents for: ConversationId: {}", conversationId);
                     for (int documentPosition = 0; documentPosition < documents.size(); documentPosition++) {
                         var document = documents.get(documentPosition);
                         createSendDocumentTasks(

@@ -85,7 +85,7 @@ private List<InputFile> getFiles() throws UnreadableJsonFileException, NoJsonFil
             throw new NoJsonFileFound("No json files found");
         }
 
-        LOGGER.info("Processing " + files.length + " files from location: " + JSON_FILE_INPUT_PATH);
+        LOGGER.info("Processing {} files from location: {}", files.length, JSON_FILE_INPUT_PATH);
 
         Arrays.stream(files)
             .peek(file -> LOGGER.info("Parsing file: {}", file.getName()))

@@ -6,16 +6,18 @@
         </encoder>
     </appender>
 
+    <appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
+        <appender-ref ref="TEXT"/>
+        <queueSize>${GP2GP_LOGGING_ASYNC_QUEUE_SIZE:-2048}</queueSize>
+        <discardingThreshold>0</discardingThreshold>
+        <neverBlock>true</neverBlock>
+        <includeCallerData>false</includeCallerData>
+    </appender>
 
     <root level="${GP2GP_ROOT_LOGGING_LEVEL:-WARN}">
-        <appender-ref ref="TEXT}"/>
+        <appender-ref ref="ASYNC"/>
     </root>
 
     <logger name="uk.nhs.adaptors.gp2gp" level="${GP2GP_LOGGING_LEVEL:-INFO}" />
-
-<!--    <logger name="uk.nhs.adaptors.gp2gp.common.service.WebClientFilterService" level="DEBUG" />-->
-<!--    <logger name="uk.nhs.adaptors.gp2gp.mhs.MhsRequestBuilder" level="DEBUG" />-->
-<!--    <logger name="uk.nhs.adaptors.gp2gp.mhs.InboundMessageHandler" level="DEBUG" />-->
-
 	<logger name="reactor.netty.http.client" level="${GP2GP_LOGGING_LEVEL:-WARN}" />
 </configuration>
@@ -0,0 +1,119 @@
+package uk.nhs.adaptors.gp2gp.common.configuration;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.Appender;
+import ch.qos.logback.core.read.ListAppender;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LogbackConfigurationTest {
+
+    public static final int MILLIS_100 = 100;
+    private Logger rootLogger;
+    private Logger gp2gpLogger;
+    private Logger reactorNettyLogger;
+
+    @BeforeEach
+    void setUp() {
+        rootLogger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
+        gp2gpLogger = (Logger) LoggerFactory.getLogger("uk.nhs.adaptors.gp2gp");
+        reactorNettyLogger = (Logger) LoggerFactory.getLogger("reactor.netty.http.client");
+    }
+
+    @Test
+    void shouldHaveAsyncAppenderOnRootLogger() {
+
+        assertThat(rootLogger.getAppender("ASYNC"))
+            .as("AsyncAppender 'ASYNC' should be attached to root logger")
+            .isNotNull();
+
+        Appender<?> appender = rootLogger.getAppender("ASYNC");
+        assertThat(appender.getClass().getSimpleName())
+            .contains("AsyncAppender");
+    }
+
+    @Test
+    void shouldHaveGp2gpLoggerConfiguredWithProperLevel() {
+        assertThat(gp2gpLogger.getEffectiveLevel())
+            .as("GP2GP logger should inherit or override level explicitly")
+            .isNotNull();
+    }
+
+    @Test
+    void shouldDecoupleReactorNettyLoggingLevelFromGp2GpLevel() {
+        Level reactorLevel = reactorNettyLogger.getEffectiveLevel();
+
+        assertThat(reactorLevel)
+            .as("Reactor Netty logger should have explicit level to decouple from GP2GP logger")
+            .isNotNull();
+    }
+
+    @Test
+    void shouldPreserveMdcInAsyncLogging() {
+
+        ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
+        listAppender.start();
+        gp2gpLogger.addAppender(listAppender);
+        gp2gpLogger.setLevel(Level.INFO);
+
+        MDC.put("ConversationId", "test-conv-123");
+        MDC.put("TaskId", "test-task-456");
+
+        gp2gpLogger.info("Test message with MDC");
+
+        try {
+            Thread.sleep(MILLIS_100);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+
+        assertThat(listAppender.list).isNotEmpty();
+
+        ILoggingEvent event = listAppender.list.getFirst();
+        assertThat(event.getMDCPropertyMap())
+            .containsEntry("ConversationId", "test-conv-123")
+            .containsEntry("TaskId", "test-task-456");
+
+        MDC.clear();
+        gp2gpLogger.detachAppender(listAppender);
+        listAppender.stop();
+    }
+
+    @Test
+    void shouldNotBlockOnLoggingIo() {
+
+        Appender<?> asyncAppender = rootLogger.getAppender("ASYNC");
+
+        assertThat(asyncAppender)
+            .as("AsyncAppender should be configured to never block producer threads")
+            .isNotNull();
+
+        assertThat(asyncAppender.getClass().getSimpleName())
+            .isEqualTo("AsyncAppender");
+    }
+
+    @Test
+    void rootLoggerShouldHaveValidTextAppenderReference() {
+
+        Appender<?> appender = rootLogger.getAppender("ASYNC");
+
+        assertThat(appender)
+            .as("Root logger should have valid ASYNC appender (wraps corrected TEXT appender)")
+            .isNotNull();
+
+        assertThat(appender.getName())
+            .as("Appender name should be ASYNC, not a default fallback")
+            .isEqualTo("ASYNC");
+    }
+}
+
+
+
+
+