Delete old Lucene write.lock file

LockCleaner.java

import java.io.File;
import java.util.Date;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class LockCleaner {

    private static final Logger logger = LoggerFactory.getLogger(LockCleaner.class);
    
    public void clearOldLockInLuceneIndexDir(File indexDir) {
        /*  Used to recover from crashes. Deleting the lock file is normally an administrative action. 
            We are assuming here that if a lock is over an hour old, the process that initially took it has died 
            and deleting it is safe.
            More context here. https://stackoverflow.com/questions/43011020/how-to-clear-the-lock-for-lucene-write-lock-file-after-a-jvm-crash
        */     
        try {
            File lockFile = new File(indexDir, "write.lock");
            long oneMinuteInMillis = 1000 * 60;
            long oneHourInMillis = 60 * oneMinuteInMillis;
            Date oneHourAgo = new Date(System.currentTimeMillis() - oneHourInMillis);
            if (isFileOlderThan(lockFile, oneHourAgo)) {
                log.warn("Found lock file in " + indexDir + " over an hour old, deleting");
                deleteQuietly(lockFile);
            }
        } catch (Exception e) {
            log.error("Error checking for old lock file.", e);
        }
    }
    
    private static boolean isFileOlderThan(File file, Date threshold) {
        return file.exists() && file.lastModified() < threshold.getTime();
    }
    
    private static boolean deleteQuietly(File file) {
        try {
            return file.delete();
        } catch (final Exception ignored) {
            return false;
        }
   }
}