| Name | Description | Default value |
| group_id | Consumer group id. Topic partition evenly distributed between consumers with the same group_id. | – |
| client_id | Client identifier. May be an arbitrary string. Optional, but you should set this property on each instance because it enables you to more easily correlate requests on the broker with the client instance which made it, which can be helpful in debugging and troubleshooting scenarios. | userver |
| topics.[] | List of topics consumer subscribes. Each of the elements: topic name. | – |
| max_batch_size | Maximum number of messages consumer waits for new messages before calling a callback. | 1 |
| poll_timeout | Maximum amount of time consumer waits for new messages before calling a callback. | 1s |
| message_key_log_format | Specifies the logging format for the message key. - 'plaintext': logs the message key as-is. - 'hex': logs the message key in hexadecimal format. Possible values: plaintext, hex. | plaintext |
| max_callback_duration | Duration user callback must fit not to be kicked from the consumer group. The duration must fit in [1ms; 86400000ms]. | 5m |
| restart_after_failure_delay | Backoff consumer waits until restart after user-callback exception. | 10s |
| auto_offset_reset | Action to take when there is no initial offset in offset store or the desired offset is out of range: smallest, earliest, beginning - automatically reset the offset to the smallest offset largest, latest, end - automatically reset the offset to the largest offset, error - trigger an error (ERR__AUTO_OFFSET_RESET). Note: the policy applies iff there are not committed offsets in topic. Possible values: smallest, earliest, beginning, largest, latest, end, error. | – |
| env_pod_name | If defined and group_id value contains {pod_name} substring, the substring is replaced with the value of the environment variable env_pod_name. | none |
| security_protocol | Protocol used to communicate with brokers. Possible values: PLAINTEXT, SASL_SSL, SASL_PLAINTEXT, SSL. | – |
| sasl_mechanisms | SASL mechanism to use for authentication. Must be set if security_protocol equals SASL_SSL. Possible values: PLAIN, SCRAM-SHA-512. | none |
| ssl_ca_location | File or directory path to CA certificate(s) for verifying the broker's key. Must be set if security_protocol equals SASL_SSL or SSL. If set to probe, CA certificates are probed from the default certificates paths. | none |
| topic_metadata_refresh_interval | Period of time at which topic and broker metadata is refreshed in order to discover any new brokers, topics, partitions or partition leader changes. | 5m |
| metadata_max_age | Metadata cache max age. Recommended value is 3 times topic_metadata_refresh_interval. | 15m |
| rd_kafka_custom_options.* | A map of arbitrary librdkafka library configuration options. Full list of options is available by link: https://github.com/confluentinc/librdkafka/blob/master/CONFIGURATION.md. Note: This options is not guaranteed to be supported in userver-kafka, use it at your own risk. Each of the elements: librdkafka option value. | {} |
| debug_info_log_level | Log level for everything debug information. | debug |
| operation_log_level | Log level for infos about ordinary actions. | debug |
