LogRetriever.java

private void fetchAndWriteLog(LogQuery query, String fileName) throws Exception {
    FileService fs = FileServiceFactory.getFileService();
    AppEngineFile file = null;
    FileWriteChannel channel = null;
    Writer writer = null;

    try {
        long start = System.currentTimeMillis();
        file = fs.createNewGSFile(new GSFileOptionsBuilder()
                .setBucket(GS_BUCKET_NAME)
                .setKey(fileName)
                .setMimeType("text/plain")
                .setAcl("project-private")
                .build());

        for (RequestLogs record : LogServiceFactory.getLogService().fetch(query)) {
            if (!"GET".equalsIgnoreCase(record.getMethod()) && !"POST".equalsIgnoreCase(record.getMethod()))
                continue;
            // 15秒に1回closeしてopenする（Cloud Storageの制約回避）
            if ((System.currentTimeMillis() - start) > 15000) {
                start = System.currentTimeMillis();
                writer.close();
                channel.close();
                Thread.sleep(1000);
            }
            if (channel == null || !channel.isOpen()) {
                channel = fs.openWriteChannel(file, true);
                writer = new BufferedWriter(Channels.newWriter(channel, "UTF8"), GS_WRITER_BUFFER_SIZE);
            }
            for (AppLogLine appLog : record.getAppLogLines()) {
                String line = appLog.getLogMessage();
                if (line.contains(ActivityLogger.STDLOG_PREFIX)) {
                    String message = line.split(ActivityLogger.STDLOG_PREFIX)[1];
                    writer.write(message);
                }
            }
        }
    } catch (Exception e) {
        logger.warning("failed to logging cloud storage.");
        throw e;
    } finally {
        try {
            if (writer != null)
                writer.close();
            if (channel != null)
                channel.closeFinally();
        } catch (Exception e) {
            logger.warning("failed to close cloud storage io channel.");
            e.printStackTrace(System.out);
        }
    }
}