GraylogExtendedLogFormatStructuredLogFormatter Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/logging/logback/GraylogExtendedLogFormatStructuredLogFormatter.java lines 58–149

class GraylogExtendedLogFormatStructuredLogFormatter extends JsonWriterStructuredLogFormatter<ILoggingEvent> {

	private static final PairExtractor<KeyValuePair> keyValuePairExtractor = PairExtractor.of((pair) -> pair.key,
			(pair) -> pair.value);

	private static final Log logger = LogFactory.getLog(GraylogExtendedLogFormatStructuredLogFormatter.class);

	/**
	 * Allowed characters in field names are any word character (letter, number,
	 * underscore), dashes and dots.
	 */
	private static final Pattern FIELD_NAME_VALID_PATTERN = Pattern.compile("^[\\w.\\-]*$");

	/**
	 * Libraries SHOULD not allow to send id as additional field ("_id"). Graylog server
	 * nodes omit this field automatically.
	 */
	private static final Set<String> ADDITIONAL_FIELD_ILLEGAL_KEYS = Set.of("id", "_id");

	GraylogExtendedLogFormatStructuredLogFormatter(Environment environment,
			@Nullable StackTracePrinter stackTracePrinter, ContextPairs contextPairs,
			ThrowableProxyConverter throwableProxyConverter,
			@Nullable StructuredLoggingJsonMembersCustomizer<?> customizer) {
		super((members) -> jsonMembers(environment, stackTracePrinter, contextPairs, throwableProxyConverter, members),
				customizer);
	}

	private static void jsonMembers(Environment environment, @Nullable StackTracePrinter stackTracePrinter,
			ContextPairs contextPairs, ThrowableProxyConverter throwableProxyConverter,
			JsonWriter.Members<ILoggingEvent> members) {
		Extractor extractor = new Extractor(stackTracePrinter, throwableProxyConverter);
		members.add("version", "1.1");
		members.add("short_message", ILoggingEvent::getFormattedMessage)
			.as(GraylogExtendedLogFormatStructuredLogFormatter::getMessageText);
		members.add("timestamp", ILoggingEvent::getTimeStamp)
			.as(GraylogExtendedLogFormatStructuredLogFormatter::formatTimeStamp);
		members.add("level", LevelToSyslogSeverity::convert);
		members.add("_level_name", ILoggingEvent::getLevel);
		members.add("_process_pid", environment.getProperty("spring.application.pid", Long.class)).whenNotNull();
		members.add("_process_thread_name", ILoggingEvent::getThreadName);
		GraylogExtendedLogFormatProperties.get(environment).jsonMembers(members);
		members.add("_log_logger", ILoggingEvent::getLoggerName);
		members.add().usingPairs(contextPairs.flat(additionalFieldJoiner(), (pairs) -> {
			pairs.addMapEntries(ILoggingEvent::getMDCPropertyMap);
			pairs.add(ILoggingEvent::getKeyValuePairs, keyValuePairExtractor);
		}));
		Function<@Nullable ILoggingEvent, @Nullable Object> getThrowableProxy = (event) -> (event != null)
				? event.getThrowableProxy() : null;
		members.add()
			.whenNotNull(getThrowableProxy)
			.usingMembers((throwableMembers) -> throwableMembers(throwableMembers, extractor));
	}

	private static String getMessageText(String formattedMessage) {
		// Always return text as a blank message will lead to a error as of Graylog v6
		return (!StringUtils.hasText(formattedMessage)) ? "(blank)" : formattedMessage;
	}

	/**
	 * GELF requires "seconds since UNIX epoch with optional <b>decimal places for
	 * milliseconds</b>". To comply with this requirement, we format a POSIX timestamp
	 * with millisecond precision as e.g. "1725459730385" -> "1725459730.385"
	 * @param timeStamp the timestamp of the log message
	 * @return the timestamp formatted as string with millisecond precision
	 */
	private static WritableJson formatTimeStamp(long timeStamp) {
		return (out) -> out.append(new BigDecimal(timeStamp).movePointLeft(3).toPlainString());
	}

	private static void throwableMembers(Members<ILoggingEvent> members, Extractor extractor) {
		members.add("full_message", extractor::messageAndStackTrace);
		members.add("_error_type", ILoggingEvent::getThrowableProxy).as(IThrowableProxy::getClassName);
		members.add("_error_stack_trace", extractor::stackTrace);
		members.add("_error_message", ILoggingEvent::getThrowableProxy).as(IThrowableProxy::getMessage);
	}

	private static Joiner additionalFieldJoiner() {
		return (prefix, name) -> {
			name = prefix + name;
			if (!FIELD_NAME_VALID_PATTERN.matcher(name).matches()) {
				logger.warn(LogMessage.format("'%s' is not a valid field name according to GELF standard", name));
				return null;
			}
			if (ADDITIONAL_FIELD_ILLEGAL_KEYS.contains(name)) {
				logger.warn(LogMessage.format("'%s' is an illegal field name according to GELF standard", name));
				return null;
			}
			return (!name.startsWith("_")) ? "_" + name : name;
		};
	}

}