Examples with SpeculativeRetryParam org.apache.cassandra.schema.SpeculativeRetryParam used on opensource projects

Example 1 with SpeculativeRetryParam

use of org.apache.cassandra.schema.SpeculativeRetryParam in project cassandra by apache.

the class AbstractReadExecutor method getReadExecutor.

/**
     * @return an executor appropriate for the configured speculative read policy
     */
public static AbstractReadExecutor getReadExecutor(SinglePartitionReadCommand command, ConsistencyLevel consistencyLevel, long queryStartNanoTime) throws UnavailableException {
    Keyspace keyspace = Keyspace.open(command.metadata().keyspace);
    List<InetAddress> allReplicas = StorageProxy.getLiveSortedEndpoints(keyspace, command.partitionKey());
    // 11980: Excluding EACH_QUORUM reads from potential RR, so that we do not miscount DC responses
    ReadRepairDecision repairDecision = consistencyLevel == ConsistencyLevel.EACH_QUORUM ? ReadRepairDecision.NONE : newReadRepairDecision(command.metadata());
    List<InetAddress> targetReplicas = consistencyLevel.filterForQuery(keyspace, allReplicas, repairDecision);
    // Throw UAE early if we don't have enough replicas.
    consistencyLevel.assureSufficientLiveNodes(keyspace, targetReplicas);
    if (repairDecision != ReadRepairDecision.NONE) {
        Tracing.trace("Read-repair {}", repairDecision);
        ReadRepairMetrics.attempted.mark();
    }
    ColumnFamilyStore cfs = keyspace.getColumnFamilyStore(command.metadata().id);
    SpeculativeRetryParam retry = cfs.metadata().params.speculativeRetry;
    // 11980: Disable speculative retry if using EACH_QUORUM in order to prevent miscounting DC responses
    if (retry.equals(SpeculativeRetryParam.NONE) || consistencyLevel == ConsistencyLevel.EACH_QUORUM || consistencyLevel.blockFor(keyspace) == allReplicas.size())
        return new NeverSpeculatingReadExecutor(keyspace, command, consistencyLevel, targetReplicas, queryStartNanoTime);
    if (targetReplicas.size() == allReplicas.size()) {
        // (same amount of requests in total, but we turn 1 digest request into a full blown data request).
        return new AlwaysSpeculatingReadExecutor(keyspace, cfs, command, consistencyLevel, targetReplicas, queryStartNanoTime);
    }
    // RRD.NONE or RRD.DC_LOCAL w/ multiple DCs.
    InetAddress extraReplica = allReplicas.get(targetReplicas.size());
    // we might have to find a replacement that's not already in targetReplicas.
    if (repairDecision == ReadRepairDecision.DC_LOCAL && targetReplicas.contains(extraReplica)) {
        for (InetAddress address : allReplicas) {
            if (!targetReplicas.contains(address)) {
                extraReplica = address;
                break;
            }
        }
    }
    targetReplicas.add(extraReplica);
    if (retry.equals(SpeculativeRetryParam.ALWAYS))
        return new AlwaysSpeculatingReadExecutor(keyspace, cfs, command, consistencyLevel, targetReplicas, queryStartNanoTime);
    else
        // PERCENTILE or CUSTOM.
        return new SpeculatingReadExecutor(keyspace, cfs, command, consistencyLevel, targetReplicas, queryStartNanoTime);
}