java kafka客户端何时设置的kafka消费者默认值

kafka为什么有些属性没有配置却能正常工作,那是因为kafka-clients对有些消费者设置了默认值,具体看下ConsumerConfig类的静态模块,具体如下所示:

复制代码
kafka为什么有些属性没有配置却能正常工作,那是因为kafka-clients对有些消费者设置了默认值,具体看下ConsumerConfig类的静态模块,具体如下所示:

static {
    CONFIG = new ConfigDef().define(BOOTSTRAP_SERVERS_CONFIG,
                                    Type.LIST,
                                    Collections.emptyList(),
                                    new ConfigDef.NonNullValidator(),
                                    Importance.HIGH,
                                    CommonClientConfigs.BOOTSTRAP_SERVERS_DOC)
                            .define(CLIENT_DNS_LOOKUP_CONFIG,
                                    Type.STRING,
                                    ClientDnsLookup.USE_ALL_DNS_IPS.toString(),
                                    in(ClientDnsLookup.DEFAULT.toString(),
                                       ClientDnsLookup.USE_ALL_DNS_IPS.toString(),
                                       ClientDnsLookup.RESOLVE_CANONICAL_BOOTSTRAP_SERVERS_ONLY.toString()),
                                    Importance.MEDIUM,
                                    CommonClientConfigs.CLIENT_DNS_LOOKUP_DOC)
                            .define(GROUP_ID_CONFIG, Type.STRING, null, Importance.HIGH, GROUP_ID_DOC)
                            .define(GROUP_INSTANCE_ID_CONFIG,
                                    Type.STRING,
                                    null,
                                    Importance.MEDIUM,
                                    GROUP_INSTANCE_ID_DOC)
                            .define(SESSION_TIMEOUT_MS_CONFIG,
                                    Type.INT,
                                    10000,
                                    Importance.HIGH,
                                    SESSION_TIMEOUT_MS_DOC)
                            .define(HEARTBEAT_INTERVAL_MS_CONFIG,
                                    Type.INT,
                                    3000,
                                    Importance.HIGH,
                                    HEARTBEAT_INTERVAL_MS_DOC)
                            .define(PARTITION_ASSIGNMENT_STRATEGY_CONFIG,
                                    Type.LIST,
                                    Collections.singletonList(RangeAssignor.class),
                                    new ConfigDef.NonNullValidator(),
                                    Importance.MEDIUM,
                                    PARTITION_ASSIGNMENT_STRATEGY_DOC)
                            .define(METADATA_MAX_AGE_CONFIG,
                                    Type.LONG,
                                    5 * 60 * 1000,
                                    atLeast(0),
                                    Importance.LOW,
                                    CommonClientConfigs.METADATA_MAX_AGE_DOC)
                            .define(ENABLE_AUTO_COMMIT_CONFIG,
                                    Type.BOOLEAN,
                                    true,
                                    Importance.MEDIUM,
                                    ENABLE_AUTO_COMMIT_DOC)
                            .define(AUTO_COMMIT_INTERVAL_MS_CONFIG,
                                    Type.INT,
                                    5000,
                                    atLeast(0),
                                    Importance.LOW,
                                    AUTO_COMMIT_INTERVAL_MS_DOC)
                            .define(CLIENT_ID_CONFIG,
                                    Type.STRING,
                                    "",
                                    Importance.LOW,
                                    CommonClientConfigs.CLIENT_ID_DOC)
                            .define(CLIENT_RACK_CONFIG,
                                    Type.STRING,
                                    "",
                                    Importance.LOW,
                                    CommonClientConfigs.CLIENT_RACK_DOC)
                            .define(MAX_PARTITION_FETCH_BYTES_CONFIG,
                                    Type.INT,
                                    DEFAULT_MAX_PARTITION_FETCH_BYTES,
                                    atLeast(0),
                                    Importance.HIGH,
                                    MAX_PARTITION_FETCH_BYTES_DOC)
                            .define(SEND_BUFFER_CONFIG,
                                    Type.INT,
                                    128 * 1024,
                                    atLeast(CommonClientConfigs.SEND_BUFFER_LOWER_BOUND),
                                    Importance.MEDIUM,
                                    CommonClientConfigs.SEND_BUFFER_DOC)
                            .define(RECEIVE_BUFFER_CONFIG,
                                    Type.INT,
                                    64 * 1024,
                                    atLeast(CommonClientConfigs.RECEIVE_BUFFER_LOWER_BOUND),
                                    Importance.MEDIUM,
                                    CommonClientConfigs.RECEIVE_BUFFER_DOC)
                            .define(FETCH_MIN_BYTES_CONFIG,
                                    Type.INT,
                                    1,
                                    atLeast(0),
                                    Importance.HIGH,
                                    FETCH_MIN_BYTES_DOC)
                            .define(FETCH_MAX_BYTES_CONFIG,
                                    Type.INT,
                                    DEFAULT_FETCH_MAX_BYTES,
                                    atLeast(0),
                                    Importance.MEDIUM,
                                    FETCH_MAX_BYTES_DOC)
                            .define(FETCH_MAX_WAIT_MS_CONFIG,
                                    Type.INT,
                                    500,
                                    atLeast(0),
                                    Importance.LOW,
                                    FETCH_MAX_WAIT_MS_DOC)
                            .define(RECONNECT_BACKOFF_MS_CONFIG,
                                    Type.LONG,
                                    50L,
                                    atLeast(0L),
                                    Importance.LOW,
                                    CommonClientConfigs.RECONNECT_BACKOFF_MS_DOC)
                            .define(RECONNECT_BACKOFF_MAX_MS_CONFIG,
                                    Type.LONG,
                                    1000L,
                                    atLeast(0L),
                                    Importance.LOW,
                                    CommonClientConfigs.RECONNECT_BACKOFF_MAX_MS_DOC)
                            .define(RETRY_BACKOFF_MS_CONFIG,
                                    Type.LONG,
                                    100L,
                                    atLeast(0L),
                                    Importance.LOW,
                                    CommonClientConfigs.RETRY_BACKOFF_MS_DOC)
                      
                            .define(AUTO_OFFSET_RESET_CONFIG,
                                    Type.STRING,
                                    "latest",  //
                                    in("latest", "earliest", "none"),
                                    Importance.MEDIUM,
                                    AUTO_OFFSET_RESET_DOC)
                            .define(CHECK_CRCS_CONFIG,
                                    Type.BOOLEAN,
                                    true,
                                    Importance.LOW,
                                    CHECK_CRCS_DOC)
                            .define(METRICS_SAMPLE_WINDOW_MS_CONFIG,
                                    Type.LONG,
                                    30000,
                                    atLeast(0),
                                    Importance.LOW,
                                    CommonClientConfigs.METRICS_SAMPLE_WINDOW_MS_DOC)
                            .define(METRICS_NUM_SAMPLES_CONFIG,
                                    Type.INT,
                                    2,
                                    atLeast(1),
                                    Importance.LOW,
                                    CommonClientConfigs.METRICS_NUM_SAMPLES_DOC)
                            .define(METRICS_RECORDING_LEVEL_CONFIG,
                                    Type.STRING,
                                    Sensor.RecordingLevel.INFO.toString(),
                                    in(Sensor.RecordingLevel.INFO.toString(), Sensor.RecordingLevel.DEBUG.toString(), Sensor.RecordingLevel.TRACE.toString()),
                                    Importance.LOW,
                                    CommonClientConfigs.METRICS_RECORDING_LEVEL_DOC)
                            .define(METRIC_REPORTER_CLASSES_CONFIG,
                                    Type.LIST,
                                    Collections.emptyList(),
                                    new ConfigDef.NonNullValidator(),
                                    Importance.LOW,
                                    CommonClientConfigs.METRIC_REPORTER_CLASSES_DOC)
                            .define(KEY_DESERIALIZER_CLASS_CONFIG,
                                    Type.CLASS,
                                    Importance.HIGH,
                                    KEY_DESERIALIZER_CLASS_DOC)
                            .define(VALUE_DESERIALIZER_CLASS_CONFIG,
                                    Type.CLASS,
                                    Importance.HIGH,
                                    VALUE_DESERIALIZER_CLASS_DOC)
                            .define(REQUEST_TIMEOUT_MS_CONFIG,
                                    Type.INT,
                                    30000,
                                    atLeast(0),
                                    Importance.MEDIUM,
                                    REQUEST_TIMEOUT_MS_DOC)
                            .define(DEFAULT_API_TIMEOUT_MS_CONFIG,
                                    Type.INT,
                                    60 * 1000,
                                    atLeast(0),
                                    Importance.MEDIUM,
                                    CommonClientConfigs.DEFAULT_API_TIMEOUT_MS_DOC)
                            .define(SOCKET_CONNECTION_SETUP_TIMEOUT_MS_CONFIG,
                                    Type.LONG,
                                    CommonClientConfigs.DEFAULT_SOCKET_CONNECTION_SETUP_TIMEOUT_MS,
                                    Importance.MEDIUM,
                                    CommonClientConfigs.SOCKET_CONNECTION_SETUP_TIMEOUT_MS_DOC)
                            .define(SOCKET_CONNECTION_SETUP_TIMEOUT_MAX_MS_CONFIG,
                                    Type.LONG,
                                    CommonClientConfigs.DEFAULT_SOCKET_CONNECTION_SETUP_TIMEOUT_MAX_MS,
                                    Importance.MEDIUM,
                                    CommonClientConfigs.SOCKET_CONNECTION_SETUP_TIMEOUT_MAX_MS_DOC)
                            /* default is set to be a bit lower than the server default (10 min), to avoid both client and server closing connection at same time */
                            .define(CONNECTIONS_MAX_IDLE_MS_CONFIG,
                                    Type.LONG,
                                    9 * 60 * 1000,
                                    Importance.MEDIUM,
                                    CommonClientConfigs.CONNECTIONS_MAX_IDLE_MS_DOC)
                            .define(INTERCEPTOR_CLASSES_CONFIG,
                                    Type.LIST,
                                    Collections.emptyList(),
                                    new ConfigDef.NonNullValidator(),
                                    Importance.LOW,
                                    INTERCEPTOR_CLASSES_DOC)
                            .define(MAX_POLL_RECORDS_CONFIG,
                                    Type.INT,
                                    500,
                                    atLeast(1),
                                    Importance.MEDIUM,
                                    MAX_POLL_RECORDS_DOC)
                            .define(MAX_POLL_INTERVAL_MS_CONFIG,
                                    Type.INT,
                                    300000,
                                    atLeast(1),
                                    Importance.MEDIUM,
                                    MAX_POLL_INTERVAL_MS_DOC)
                            .define(EXCLUDE_INTERNAL_TOPICS_CONFIG,
                                    Type.BOOLEAN,
                                    DEFAULT_EXCLUDE_INTERNAL_TOPICS,
                                    Importance.MEDIUM,
                                    EXCLUDE_INTERNAL_TOPICS_DOC)
                            .defineInternal(LEAVE_GROUP_ON_CLOSE_CONFIG,
                                    Type.BOOLEAN,
                                    true,
                                    Importance.LOW)
                            .defineInternal(THROW_ON_FETCH_STABLE_OFFSET_UNSUPPORTED,
                                    Type.BOOLEAN,
                                    false,
                                    Importance.LOW)
                            .define(ISOLATION_LEVEL_CONFIG,
                                    Type.STRING,
                                    DEFAULT_ISOLATION_LEVEL,
                                    in(IsolationLevel.READ_COMMITTED.toString().toLowerCase(Locale.ROOT), IsolationLevel.READ_UNCOMMITTED.toString().toLowerCase(Locale.ROOT)),
                                    Importance.MEDIUM,
                                    ISOLATION_LEVEL_DOC)
                            .define(ALLOW_AUTO_CREATE_TOPICS_CONFIG,
                                    Type.BOOLEAN,
                                    DEFAULT_ALLOW_AUTO_CREATE_TOPICS,
                                    Importance.MEDIUM,
                                    ALLOW_AUTO_CREATE_TOPICS_DOC)
                            // security support
                            .define(SECURITY_PROVIDERS_CONFIG,
                                    Type.STRING,
                                    null,
                                    Importance.LOW,
                                    SECURITY_PROVIDERS_DOC)
                            .define(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG,
                                    Type.STRING,
                                    CommonClientConfigs.DEFAULT_SECURITY_PROTOCOL,
                                    Importance.MEDIUM,
                                    CommonClientConfigs.SECURITY_PROTOCOL_DOC)
                            .withClientSslSupport()
                            .withClientSaslSupport();
}

像auto.offset.reset这个配置默认值为latest一样,再看下ConsumerConfig的几个构造方法

复制代码
    public ConsumerConfig(Properties props) {
        super(CONFIG, props);
    }

    public ConsumerConfig(Map<String, Object> props) {
        super(CONFIG, props);
    }

是的,所有的ConsumerConfig构造方法都将上面的默认配置CONFIG传入了构造方法,将下来的处理就是如果显式配置了对应的配置项就使用显式配置数据,没有则使用CONFIG里面的默认配置。

PS:

上面的默认配置除了有一些配置的默认配置,一些枚举属性还有其可选值,比如

复制代码
auto.offset.reset的可选项
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