Я наконец-то нашел решение.Спасибо @Alexander в комментариях к подсказке.
Short: Мы можем вручную инициализировать процесс ролловера при обнаружении удаления файла.
Longer:
Я реализую это следующим образом:
1) Создайте FileWatchService, который (1) подпишется на события удаления файла журнала в вашей папке журнала и (2) уведомит вас, когда эти события произойдут.Это можно сделать с помощью java.nio.file.WatchService (https://docs.oracle.com/javase/tutorial/essential/io/notification.html).. Я предоставлю свой код ниже.
2) Создайте некоторый другой класс, который будет инициализировать опрокидывание, когда FileWatchService сообщит об удалении файла.Я также предоставлю свой полный код ниже, но основное волшебство будет происходить следующим образом:
final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
// You should know only appender name.
RollingFileAppender appender = (RollingFileAppender) ctx.getConfiguration().getAppenders().get(appenderName);
if (appender != null) {
// Manually start rollover logic.
appender.getManager().rollover();
}
Мой код выглядит так (не идеально, но он работает для меня):
FileWatchService:
public class FileWatchService implements Runnable {
private final org.apache.logging.log4j.Logger logger = LogManager.getLogger(FileWatchService.class);
private WatchService watchService = null;
private Map<WatchKey,Path> keys = null;
private String tempPath;
public FileWatchService(String tempPath) {
try {
this.watchService = FileSystems.getDefault().newWatchService();
this.keys = new HashMap<WatchKey,Path>();
this.tempPath = tempPath;
Path path = Paths.get(tempPath);
register(path);
logger.info("Watch service has been initiated.");
}
catch (Exception e) {
logger.error("The error occurred in process of registering watch service", e);
}
}
// Method which register folder to watch service.
private void register(Path tempPath) throws IOException {
logger.debug("Registering folder {} for watching.", tempPath.getFileName());
// Registering only for delete events.
WatchKey key = tempPath.register(watchService, ENTRY_DELETE);
keys.put(key, tempPath);
}
@Override
public void run() {
try {
Thread.currentThread().setName("FileWatchService");
this.processEvents();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void processEvents() throws InterruptedException {
WatchKey key;
// Waiting until event occur.
while ((key = watchService.take()) != null) {
// Poll all events when event occur.
for (WatchEvent<?> event : key.pollEvents()) {
// Getting type of event - delete, modify or create.
WatchEvent.Kind kind = event.kind();
// We are interested only for delete events.
if (kind == ENTRY_DELETE) {
// Sending "notification" to appender watcher service.
logger.debug("Received event about file deletion. File: {}", event.context());
AppenderWatcher.hadleLogFileDeletionEvent(this.tempPath + event.context());
}
}
key.reset();
}
}
}
Еще один класс для ролловера инициализации (я назвал его AppenderWatcher):
public class AppenderWatcher {
private static final org.apache.logging.log4j.Logger logger = LogManager.getLogger(AppenderWatcher.class);
public static void hadleLogFileDeletionEvent(String logFile) {
File file = new File(logFile);
if (!checkFileExist(file)) {
logger.info("File {} is not exist. Starting manual rollover...", file.toString());
// Getting possible appender name by log-file.
String appenderName = getAppenderNameByFileName(logFile);
// Getting appender from list of all appender
RollingFileAppender appender = (RollingFileAppender) getAppender(appenderName);
if (appender != null) {
// Manually start rollover logic.
appender.getManager().rollover();
logger.info("Rollover finished");
}
else {
logger.error("Can't get appender {}. Please, check lo4j2 config.", appenderName);
}
} else {
logger.warn("Received notification what file {} was deleted, but it exist.", file.getAbsolutePath());
}
}
// Method which checks is file exist. It need to prevent conflicts with Log4J rolling file logic.
// When Log4j rotate file it deletes it first and create after.
private static boolean checkFileExist(File logFile) {
return logFile.exists();
}
// Method which gets appender by name from list of all configured appenders.
private static Appender getAppender(String appenderName) {
final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
return ctx.getConfiguration().getAppenders().get(appenderName);
}
// Method which returns name of appender by log file name.
// ===Here I'm explaining some customer specific moments of log4j config.
private static String getAppenderNameByFileName(String fileName) {
return getLoggerNameByFileName(fileName) + "_LOG";
}
// This method fully customer specific.
private static String getLoggerNameByFileName(String fileName) {
// File name looks like "../log/temp/uber.log" (example).
String[] parts = fileName.split("/");
// Last part should look like "uber.log"
String lastPart = parts[parts.length - 1];
// We need only "uber" part.
String componentName = lastPart.substring(0, lastPart.indexOf("."));
return componentName.toUpperCase();
}
}