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使用java的cassandra中的高频插入会丢失一些数据

cassandra java

Vickie Jack · 技术社区 · 7 年前

我有5000000个插入查询文件。我想从文件中读取它们,并使用java驱动程序和executeAsync方法,在循环语句中写入cassandra,如以下代码所示:

public static void main(String[] args) {
        FileReader fr = null;
        try {
            fr = new FileReader("the-file-name.txt");
            BufferedReader br = new BufferedReader(fr);
            String sCurrentLine;
            long time1 = System.currentTimeMillis();
            while ((sCurrentLine = br.readLine()) != null) {
                session.executeAsync(sCurrentLine);
            }

            System.out.println(System.currentTimeMillis() - time1);
            fr.close();
            br.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

我的表定义是:

CREATE TABLE test.climate (
    city text,
    date text,
    time text,
    temprature int,
    PRIMARY KEY ((city, date), time)
) WITH CLUSTERING ORDER BY (time ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';

但运行程序后,表中的行数为2569725

cqlsh:test> select count(*) from climate ;

 count
---------
 2569725

我测试了10多次,每次select count(*)的结果都在2400,00到2600000之间

1 回复 | 直到 7 年前

Chris Lohfink 7 年前

您正在以比执行更快的速度发出异步插入,因此它们最终会超过队列大小并失败。您可以增加队列大小,这会起作用,但之后您只会对内存施加背压,而不是对生产者施加背压,并且仍然可能遇到问题。尝试限制飞行中的查询,如:

public static void main2(String[] args) {
    FileReader fr = null;
    int permits = 256;
    Semaphore l = new Semaphore(permits);
    try {
        fr = new FileReader("the-file-name.txt");
        BufferedReader br = new BufferedReader(fr);
        String sCurrentLine;
        long time1 = System.currentTimeMillis();
        while ((sCurrentLine = br.readLine()) != null) {
            l.acquire();
            session.executeAsync(sCurrentLine)
                .addListener(()->l.release(), MoreExecutors.directExecutor());
        }
        l.acquire(permits);

        System.out.println(System.currentTimeMillis() - time1);
        fr.close();
        br.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

它可能会运行得同样快,只需要找到合适大小的信号量。还要注意阻塞,直到所有许可都返回为止(在末尾获取max),否则您可以在发送所有可能在队列中的请求之前关闭jvm。

免责声明:我没有测试上述代码