Cassandra Datastax 驱动程序重试策略

Question

我们可以像这样创建一个集群实例。

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

我们是否会提供有关在查询时必须重试请求的次数的信息。

任何建议表示赞赏。

谢谢

Answer 1

为了指定这些值，您必须创建自己的 RetryPolicy interface 实现。 .

以下只是一个例子 -- 按照您的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();
    }

}

这真的很容易做到......然后你在你的 Cluster中传递它...

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

哈，
卡罗