总结7

NodeApiVersions

/**
 * An internal class which represents the API versions supported by a particular node.
 */
public class NodeApiVersions {

    // A map of the usable versions of each API, keyed by the ApiKeys instance
    private final Map<ApiKeys, ApiVersion> supportedVersions = new EnumMap<>(ApiKeys.class);

    // List of APIs which the broker supports, but which are unknown to the client
    private final List<ApiVersion> unknownApis = new ArrayList<>();

NetworkClient

/**
 * A network client for asynchronous request/response network i/o. This is an internal class used to implement the
 * user-facing producer and consumer clients.
 * <p>
 * This class is not thread-safe!
 */
public class NetworkClient implements KafkaClient {

    private enum State {
        ACTIVE,
        CLOSING,
        CLOSED
    }

    private final Logger log;

    /* the selector used to perform network i/o */
    private final Selectable selector;

    private final MetadataUpdater metadataUpdater;

    private final Random randOffset;

    /* the state of each node's connection */
    private final ClusterConnectionStates connectionStates;

    /* the set of requests currently being sent or awaiting a response */
    private final InFlightRequests inFlightRequests;

    /* the socket send buffer size in bytes */
    private final int socketSendBuffer;

    /* the socket receive size buffer in bytes */
    private final int socketReceiveBuffer;

    /* the client id used to identify this client in requests to the server */
    private final String clientId;

    /* the current correlation id to use when sending requests to servers */
    private int correlation;

    /* default timeout for individual requests to await acknowledgement from servers */
    private final int defaultRequestTimeoutMs;

    /* time in ms to wait before retrying to create connection to a server */
    private final long reconnectBackoffMs;

    private final Time time;

    /**
     * True if we should send an ApiVersionRequest when first connecting to a broker.
     */
    private final boolean discoverBrokerVersions;

    private final ApiVersions apiVersions;

    private final Map<String, ApiVersionsRequest.Builder> nodesNeedingApiVersionsFetch = new HashMap<>();

    private final List<ClientResponse> abortedSends = new LinkedList<>();

    private final Sensor throttleTimeSensor;

    private final AtomicReference<State> state;