Question

我尝试使用official Cassandra and Scylla documentation中描述的预准备语句，但是对于100,000条消息，性能仍然是大约30秒。任何想法如何才能改善这一点？

query = "INSERT INTO message (id, message) VALUES (?, ?)"
prepared = session.prepare(query)
for key in range(100000):

    try:
        session.execute_async(prepared, (0, "my example message"))
    except Exception as e:
        print("An error occured : " + str(e))
        pass

更新

我发现信息强烈建议使用批次来提高性能，因此我根据官方文档使用了预处理语句和批处理。我的代码目前以这种方式看待：

print("time 0: " + str(datetime.now()))
query = "INSERT INTO message (id, message) VALUES (uuid(), ?)"
prepared = session.prepare(query)

for key in range(100):

    print(key)

    try:

        batch = BatchStatement(consistency_level=ConsistencyLevel.QUORUM)
        for key in range(100):

            batch.add(prepared, ("example message",))

        session.execute(batch)

    except Exception as e:
        print("An error occured : " + str(e))
        pass

print("time 1: " + str(datetime.now()))

您是否知道为什么性能如此之慢？运行此源代码后，结果如下所示？

test 0: 2018-06-19 11:10:13.990691
0
1
...
41
cAn error occured : Error from server: code=1100 [Coordinator node timed out waiting for replica nodes' responses] message="Operation timed out for messages.message - received only 1 responses from 2 CL=QUORUM." info={'write_type': 'BATCH', 'required_responses': 2, 'consistency': 'QUORUM', 'received_responses': 1}
42
...
52                                                                                                                                                                             An error occured : errors={'....0.3': 'Client request timeout. See Session.execute[_async](timeout)'}, last_host=.....0.3
53
An error occured : Error from server: code=1100 [Coordinator node timed out waiting for replica nodes' responses] message="Operation timed out for messages.message - received only 1 responses from 2 CL=QUORUM." info={'write_type': 'BATCH', 'required_responses': 2, 'consistency': 'QUORUM', 'received_responses': 1}
54
...
59
An error occured : Error from server: code=1100 [Coordinator node timed out waiting for replica nodes' responses] message="Operation timed out for messages.message - received only 1 responses from 2 CL=QUORUM." info={'write_type': 'BATCH', 'required_responses': 2, 'consistency': 'QUORUM', 'received_responses': 1}
60
61
62
...
69
70
71
An error occured : errors={'.....0.2': 'Client request timeout. See Session.execute[_async](timeout)'}, last_host=.....0.2
72
An error occured : errors={'....0.1': 'Client request timeout. See Session.execute[_async](timeout)'}, last_host=....0.1
73
74
...
98
99
test 1: 2018-06-19 11:11:03.494957

Answer 1

在我的计算机上，通过严重并行化插入内容，使用本地计算机可以获得此类问题的次执行时间。

➜  loadz ./loadz
execution time: 951.701622ms

恐怕我不知道如何在Python中进行操作，但是在Go语言中，它看起来可能像这样：

package main

import (
  "fmt"
  "sync"
  "time"

  "github.com/gocql/gocql"
)

func main() {
  cluster := gocql.NewCluster("127.0.0.1")
  cluster.Keyspace = "mykeyspace"

  session, err := cluster.CreateSession()
  if err != nil {
      panic(err)
  }
  defer session.Close()

  workers := 1000
  ch := make(chan *gocql.Query, 100001)
  wg := &sync.WaitGroup{}
  wg.Add(workers)

  for i := 0; i < workers; i++ {
      go func() {
          defer wg.Done()
          for q := range ch {
              if err := q.Exec(); err != nil {
                  fmt.Println(err)
              }
          }
      }()
  }

  start := time.Now()
  for i := 0; i < 100000; i++ {
      ch <- session.Query("INSERT INTO message (id,message) VALUES (uuid(),?)", "the message")
  }
  close(ch)
  wg.Wait()
  dur := time.Since(start)
  fmt.Printf("execution time: %s\n", dur)
}

如果您想进行测试，请根据需要调整连接参数。

如何提高向ScyllaDB添加数据的性能？

1 个答案: