Cassandra DataStax驱动程序重试策略

Question

我们可以创建一个类似的群集实例。

 cluster = Cluster
.builder()
.addContactPoint("192.168.0.30")
.withRetryPolicy(DefaultRetryPolicy.INSTANCE)
.build();

是，我们将提供有关在查询时必须重新请求的时间数量的信息。

任何建议都将不胜感激。

谢谢

Answer 1

为了指定这些值，您必须创建自己的RetryPolicy接口实现。

以下只是一个示例 - 按照规则进行自己的实现：

public class CustomRetryPolicy implements RetryPolicy {
    private final int readAttempts;
    private final int writeAttempts;
    private final int unavailableAttempts;
    public CustomRetryPolicy(int readAttempts, int writeAttempts, int unavailableAttempts) {
        this.readAttempts = readAttempts;
        this.writeAttempts = writeAttempts;
        this.unavailableAttempts = unavailableAttempts;
    }
    @Override
    public RetryDecision onReadTimeout(Statement stmnt, ConsistencyLevel cl, int requiredResponses, int receivedResponses, boolean dataReceived, int rTime) {
        if (dataReceived) {
            return RetryDecision.ignore();
        } else if (rTime < readAttempts) {
            return RetryDecision.retry(cl);
        } else {
            return RetryDecision.rethrow();
        }
    }
    @Override
    public RetryDecision onWriteTimeout(Statement stmnt, ConsistencyLevel cl, WriteType wt, int requiredResponses, int receivedResponses, int wTime) {
        if (wTime < writeAttempts) {
            return RetryDecision.retry(cl);
        }
        return RetryDecision.rethrow();
    }
    @Override
    public RetryDecision onUnavailable(Statement stmnt, ConsistencyLevel cl, int requiredResponses, int receivedResponses, int uTime) {
                if (uTime < unavailableAttempts) {
            return RetryDecision.retry(ConsistencyLevel.ONE);
        }
        return RetryDecision.rethrow();
    }
}

这真的很容易做...然后您将其传递到Cluster ...

RetryPolicy rc = new CustomRetryPolicy(3, 3, 2);
Cluster cluster = Cluster.builder().addContactPoint("192.168.0.30").withRetryPolicy(rc).build();

hth，卡洛

Answer 2

对于任何C＃使用Cassandracsharpdriver nuget软件包的开发人员，我无耻地复制了Carlo bertuccini的出色答案，并转换为C＃Syntax：

CustomRetryPolicy customRetryPolicy = new CustomRetryPolicy(10, 10, 10);
cluster = Cluster.Builder().WithRetryPolicy(customRetryPolicy).WithCredentials(USER, PASS).AddContactPoint(NODE).WithCompression(CompressionType.Snappy).Build();

类：

public class CustomRetryPolicy : IRetryPolicy
{
    private int readAttempts;
    private int writeAttempts;
    private int unavailableAttempts;
    public CustomRetryPolicy(int readAttempts, int writeAttempts, int unavailableAttempts)
    {
        this.readAttempts = readAttempts;
        this.writeAttempts = writeAttempts;
        this.unavailableAttempts = unavailableAttempts;
    }
    public RetryDecision OnReadTimeout(IStatement query, ConsistencyLevel cl, int requiredResponses, int receivedResponses, bool dataRetrieved, int nbRetry)
    {
        if (dataRetrieved)
        {
            return RetryDecision.Ignore();
        }
        else if (nbRetry < readAttempts)
        {
            return RetryDecision.Retry(cl);
        }
        else
        {
            return RetryDecision.Rethrow();
        }
    }
    public RetryDecision OnUnavailable(IStatement query, ConsistencyLevel cl, int requiredReplica, int aliveReplica, int nbRetry)
    {
        if (nbRetry < unavailableAttempts)
        {
            return RetryDecision.Retry(ConsistencyLevel.One);
        }
        return RetryDecision.Rethrow();
    }
    public RetryDecision OnWriteTimeout(IStatement query, ConsistencyLevel cl, string writeType, int requiredAcks, int receivedAcks, int nbRetry)
    {
        if (nbRetry < writeAttempts)
        {
            return RetryDecision.Retry(cl);
        }
        return RetryDecision.Rethrow();
    }
}