AstyanaxBlockedDataReaderDAO.java 文件源码

/**
 * Gets the topology for a Cassandra keyspace as a Multimap, where the keys identify a rack (or availability zone
 * in Amazon) and the values are the token ranges for each host in that rack.  For example, for a well distributed
 * ring of 12 hosts and a replication factor of 3 this method would return a Multimap with 3 keys and each key would
 * contain 4 token ranges.
 */
private Multimap<String, TokenRange> describeCassandraTopology(final Keyspace keyspace) {
    try {
        @SuppressWarnings ("unchecked")
        ConnectionPool<Cassandra.Client> connectionPool = (ConnectionPool<Cassandra.Client>) keyspace.getConnectionPool();

        return connectionPool.executeWithFailover(
                new AbstractKeyspaceOperationImpl<Multimap<String, TokenRange>>(EmptyKeyspaceTracerFactory.getInstance().newTracer(CassandraOperationType.DESCRIBE_RING), keyspace.getKeyspaceName()) {
                    @Override
                    protected Multimap<String, TokenRange> internalExecute(Cassandra.Client client, ConnectionContext state)
                            throws Exception {
                        Multimap<String, TokenRange> racks = ArrayListMultimap.create();
                        for (org.apache.cassandra.thrift.TokenRange tokenRange : client.describe_local_ring(getKeyspace())) {
                            // The final local endpoint "owns" the token range, the rest are for replication
                            EndpointDetails endpointDetails = Iterables.getLast(tokenRange.getEndpoint_details());
                            racks.put(endpointDetails.getRack(),
                                    new TokenRangeImpl(tokenRange.getStart_token(), tokenRange.getEnd_token(), tokenRange.getEndpoints()));
                        }
                        return Multimaps.unmodifiableMultimap(racks);
                    }
                },
                keyspace.getConfig().getRetryPolicy().duplicate()).getResult();
    } catch (ConnectionException e) {
        throw Throwables.propagate(e);
    }
}