Unit tests for BufferingAppender

Author: phipag

examples/powertools-examples-core-utilities/sam/src/main/resources/log4j2.xml

@@ -4,7 +4,7 @@
         <Console name="JsonAppender" target="SYSTEM_OUT">
             <JsonTemplateLayout eventTemplateUri="classpath:LambdaJsonLayout.json" />
         </Console>
-        <BufferingAppender name="BufferedAppender" bufferAtVerbosity="DEBUG">
+        <BufferingAppender name="BufferedAppender" bufferAtVerbosity="DEBUG" maxBytes="8">
             <AppenderRef ref="JsonAppender" />
         </BufferingAppender>
     </Appenders>

powertools-logging/powertools-logging-log4j/src/test/java/software/amazon/lambda/powertools/logging/log4j/BufferingAppenderTest.java

@@ -0,0 +1,117 @@
+package software.amazon.lambda.powertools.logging.log4j;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.contentOf;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junitpioneer.jupiter.ClearEnvironmentVariable;
+
+class BufferingAppenderTest {
+
+    private Logger logger;
+
+    @BeforeEach
+    void setUp() throws IOException {
+        logger = LogManager.getLogger(BufferingAppenderTest.class);
+
+        try {
+            FileChannel.open(Paths.get("target/logfile.json"), StandardOpenOption.WRITE).truncate(0).close();
+        } catch (NoSuchFileException e) {
+            // may not be there in the first run
+        }
+    }
+
+    @AfterEach
+    void cleanUp() throws IOException {
+        FileChannel.open(Paths.get("target/logfile.json"), StandardOpenOption.WRITE).truncate(0).close();
+    }
+
+    @Test
+    void shouldBufferDebugLogsAndFlushOnError() {
+        // When - log debug messages (should be buffered)
+        logger.debug("Debug message 1");
+        logger.debug("Debug message 2");
+
+        // Then - no logs written yet
+        File logFile = new File("target/logfile.json");
+        assertThat(contentOf(logFile)).isEmpty();
+
+        // When - log error (should flush buffer)
+        logger.error("Error message");
+
+        // Then - all logs written
+        assertThat(contentOf(logFile))
+                .contains("Debug message 1")
+                .contains("Debug message 2")
+                .contains("Error message");
+    }
+
+    @Test
+    @ClearEnvironmentVariable(key = "_X_AMZN_TRACE_ID")
+    void shouldLogDirectlyWhenNoTraceId() {
+        // When
+        logger.debug("Debug without trace");
+
+        // Then - log written directly
+        File logFile = new File("target/logfile.json");
+        assertThat(contentOf(logFile)).contains("Debug without trace");
+    }
+
+    @Test
+    void shouldNotBufferInfoLogs() {
+        // When - log info message (above buffer level)
+        logger.info("Info message");
+
+        // Then - log written directly
+        File logFile = new File("target/logfile.json");
+        assertThat(contentOf(logFile)).contains("Info message");
+    }
+
+    @Test
+    void shouldFlushBufferManually() {
+        // When - buffer debug logs
+        logger.debug("Buffered message");
+        File logFile = new File("target/logfile.json");
+        assertThat(contentOf(logFile)).isEmpty();
+
+        // When - manual flush
+        BufferingAppender appender = getBufferingAppender();
+        appender.flushBuffer();
+
+        // Then - logs written
+        assertThat(contentOf(logFile)).contains("Buffered message");
+    }
+
+    @Test
+    void shouldClearBufferManually() {
+        // When - buffer debug logs then clear
+        logger.debug("Buffered message");
+        BufferingAppender appender = getBufferingAppender();
+        appender.clearBuffer();
+
+        // When - log error (should not flush cleared buffer)
+        logger.error("Error after clear");
+
+        // Then - only error logged
+        File logFile = new File("target/logfile.json");
+        assertThat(contentOf(logFile))
+                .contains("Error after clear")
+                .doesNotContain("Buffered message");
+    }
+
+    private BufferingAppender getBufferingAppender() {
+        return (BufferingAppender) ((org.apache.logging.log4j.core.LoggerContext) LogManager.getContext(false))
+                .getConfiguration().getAppender(BufferingAppenderConstants.NAME);
+    }
+}

powertools-logging/powertools-logging-log4j/src/test/resources/log4j2.xml

@@ -10,8 +10,17 @@
         <File name="logFileWithEcs" fileName="target/ecslogfile.json">
             <JsonTemplateLayout eventTemplateUri="classpath:LambdaEcsLayout.json" />
         </File>
+        <BufferingAppender name="BufferingAppender" 
+                          bufferAtVerbosity="DEBUG" 
+                          maxBytes="1024" 
+                          flushOnErrorLog="true">
+            <AppenderRef ref="logFile"/>
+        </BufferingAppender>
     </Appenders>
-    <Loggers>q
+    <Loggers>
+        <Logger name="software.amazon.lambda.powertools.logging.log4j.BufferingAppenderTest" level="DEBUG" additivity="false">
+            <AppenderRef ref="BufferingAppender"/>
+        </Logger>
         <Logger name="software.amazon.lambda.powertools" level="DEBUG" additivity="false">
             <AppenderRef ref="logFileWithEcs"/>
             <AppenderRef ref="logFile"/>