checkpoint

設置checkpoint存儲目錄，從最新的checkpoint恢復：

JavaStreamingContext ssc = JavaStreamingContext.getOrCreate(checkpointDirectory,
                ()-> createContext(ip,port,outputPath,checkpointDirectory));

createContext(String ip, int port, String outputPath, String checkpointDirectory)：

public static JavaStreamingContext createContext(String ip, int port, String outputPath, String checkpointDirectory) {

        //程序第一運行時會創建該條語句，如果應用程序失敗，則會從checkpoint中恢復，該條語句不會執
        SparkConf sparkConf = new SparkConf().setAppName("RecoverableNetworkWordCount").setMaster("local");
        // Create the context with a 1 second batch size
        JavaStreamingContext ssc = new JavaStreamingContext(sparkConf, Durations.seconds(1));
        ssc.checkpoint(checkpointDirectory);

        return  ssc;
    }