public static boolean nowLoggingTo(String filename) {
        if (filename.contains("\n")) {
            throw new IllegalArgumentException("Cannot use filename with newline: "+filename);
        }
        long s = System.currentTimeMillis() / 1000;
        String meta = "" + s + " " + filename + "\n";
        byte[] data = meta.getBytes(UTF_8);
        try (OutputStream out = metaFile()) {
            out.write(data);
        } catch (java.io.IOException e) {
            System.err.println("Saving meta-data about logfile "+filename+" failed: "+e);
            return false;
        }
        return true;
    }
@Test
    public void canSave() {
        System.err.println("VH: "+System.getenv("VESPA_HOME"));
        File dir = new File(getDefaults().underVespaHome(LogFileDb.DBDIR));
        assertTrue(!dir.exists() || IOUtils.recursiveDeleteDir(dir));
        System.err.println("using directory: "+dir);
        File extraDir = new File(getDefaults().underVespaHome("logs/extra"));
        assertTrue(!extraDir.exists() || IOUtils.recursiveDeleteDir(extraDir));
        String fn = getDefaults().underVespaHome("logs/extra/foo-bar.log");
        assertTrue(LogFileDb.nowLoggingTo(fn));
        fn = getDefaults().underVespaHome("logs/extra/stamped-1.log");
        assertTrue(LogFileDb.nowLoggingTo(fn));
    }