Datastax Java 驅動程序自定義重試策略

Question

我編寫了一個自定義重試策略類，我可以在其中傳遞沒有重試驅動程序將執行 onWriteTimeout/onUnavilable/onReadTimeout。

public class CustomRetryPolicy implements RetryPolicy {


  private static final Logger LOG = LoggerFactory.getLogger(CustomRetryPolicy.class);

  @VisibleForTesting
  public static final String RETRYING_ON_READ_TIMEOUT =
      "[{}] Retrying on read timeout on same host (consistency: {}, required responses: {}, "
          + "received responses: {}, data retrieved: {}, retries: {})";

  @VisibleForTesting
  public static final String RETRYING_ON_WRITE_TIMEOUT =
      "[{}] Retrying on write timeout on same host (consistency: {}, write type: {}, "
          + "required acknowledgments: {}, received acknowledgments: {}, retries: {})";

  @VisibleForTesting
  public static final String RETRYING_ON_UNAVAILABLE =
      "[{}] Retrying on unavailable exception on next host (consistency: {}, "
          + "required replica: {}, alive replica: {}, retries: {})";

  @VisibleForTesting
  public static final String RETRYING_ON_ABORTED =
      "[{}] Retrying on aborted request on next host (retries: {})";

  @VisibleForTesting
  public static final String RETRYING_ON_ERROR =
      "[{}] Retrying on node error on next host (retries: {})";

  private static final String LOG_PREFIX = "DATASTORE-CASSANDRA";

  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(Request request, ConsistencyLevel cl, int blockFor,
      int received, boolean dataPresent, int retryCount) {


    RetryDecision decision = (retryCount < readAttempts && received >= blockFor && !dataPresent)
        ? RetryDecision.RETRY_SAME
        : RetryDecision.RETHROW;

    if (decision == RetryDecision.RETRY_SAME && LOG.isTraceEnabled()) {
      LOG.trace(RETRYING_ON_READ_TIMEOUT, LOG_PREFIX, cl, blockFor, received, false, retryCount);
    }

    return decision;
  }



  @Override
  public RetryDecision onWriteTimeout(Request request, ConsistencyLevel cl, WriteType writeType,
      int blockFor, int received, int retryCount) {
    RetryDecision decision = (retryCount < writeAttempts && writeType == DefaultWriteType.BATCH_LOG)
        ? RetryDecision.RETRY_SAME
        : RetryDecision.RETHROW;

    if (decision == RetryDecision.RETRY_SAME && LOG.isTraceEnabled()) {
      LOG.trace(RETRYING_ON_WRITE_TIMEOUT, LOG_PREFIX, cl, writeType, blockFor, received,
          retryCount);
    }
    return decision;
  }

  @Override
  public RetryDecision onUnavailable(Request request, ConsistencyLevel cl, int required, int alive,
      int retryCount) {
    RetryDecision decision =
        (retryCount < unavailableAttempts) ? RetryDecision.RETRY_NEXT : RetryDecision.RETHROW;

    if (decision == RetryDecision.RETRY_NEXT && LOG.isTraceEnabled()) {
      LOG.trace(RETRYING_ON_UNAVAILABLE, LOG_PREFIX, cl, required, alive, retryCount);
    }

    return decision;
  }

  @Override
  public RetryDecision onRequestAborted(Request request, Throwable error, int retryCount) {
    RetryDecision decision =
        (error instanceof ClosedConnectionException || error instanceof HeartbeatException)
            ? RetryDecision.RETRY_NEXT
            : RetryDecision.RETHROW;

    if (decision == RetryDecision.RETRY_NEXT && LOG.isTraceEnabled()) {
      LOG.trace(RETRYING_ON_ABORTED, LOG_PREFIX, retryCount, error);
    }

    return decision;
  }

  @Override
  public RetryDecision onErrorResponse(Request request, CoordinatorException error,
      int retryCount) {
    RetryDecision decision =
        (error instanceof ReadFailureException || error instanceof WriteFailureException)
            ? RetryDecision.RETHROW
            : RetryDecision.RETRY_NEXT;

    if (decision == RetryDecision.RETRY_NEXT && LOG.isTraceEnabled()) {
      LOG.trace(RETRYING_ON_ERROR, LOG_PREFIX, retryCount, error);
    }

    return decision;
  }

  @Override
  public void close() {

    // Nothing to do

  }



}

我正在使用 datastax java 驅動程序 4.6.0。 但問題是我不能用 CQLSessionBuilder 傳遞這個類的對象，這可以通過像

RetryPolicy rc = new CustomRetryPolicy(3, 3, 2);
Cluster cluster = Cluster.builder().addContactPoint("192.168.0.0").withRetryPolicy(rc).build();

在舊版本的驅動程序中。 我已經嘗試過 DriverConfigLoader，但只有選項可以傳遞自定義類名。

你能建議嗎。

Answer 1

如果您查看DefaultRetryPolicy 的實現和CustomRetryPolicy 的示例，您將看到兩者都接收 2 個參數： DriverContext類型的context和帶有配置文件名稱的字符串。 然后您應該能夠使用context通過getConfig調用獲取DriverConfig ，然后在 config 上使用getProfile來提取自定義策略所需的配置值 - 您可以將自己的配置值放入配置文件並在重試中使用它政策，是這樣的：

datastax-java-driver {
  advanced.retry-policy {
    class = DefaultRetryPolicy
  }
  profiles {
    custom-retries {
      advanced.retry-policy {
        class = CustomRetryPolicy
        custom-policy {
           read-attempts = 3
           write-attempts = 2
           ...
        }
      }
    }
  }
}