Appendix B. Topic configuration parameters cleanup.policy Type: list Default: delete Valid Values: [compact, delete] Server Default Property: log.cleanup.policy Importance: medium A string that is either "delete" or "compact" or both. This string designates the retention policy to use on old log segments. The default policy ("delete") will discard old segments when their retention time or size limit has been reached. The "compact" setting will enable log compaction on the topic. compression.type Type: string Default: producer Valid Values: [uncompressed, zstd, lz4, snappy, gzip, producer] Server Default Property: compression.type Importance: medium Specify the final compression type for a given topic. This configuration accepts the standard compression codecs ('gzip', 'snappy', 'lz4', 'zstd'). It additionally accepts 'uncompressed' which is equivalent to no compression; and 'producer' which means retain the original compression codec set by the producer. delete.retention.ms Type: long Default: 86400000 (1 day) Valid Values: [0,... ] Server Default Property: log.cleaner.delete.retention.ms Importance: medium The amount of time to retain delete tombstone markers for log compacted topics. This setting also gives a bound on the time in which a consumer must complete a read if they begin from offset 0 to ensure that they get a valid snapshot of the final stage (otherwise delete tombstones may be collected before they complete their scan). file.delete.delay.ms Type: long Default: 60000 (1 minute) Valid Values: [0,... ] Server Default Property: log.segment.delete.delay.ms Importance: medium The time to wait before deleting a file from the filesystem. flush.messages Type: long Default: 9223372036854775807 Valid Values: [0,... ] Server Default Property: log.flush.interval.messages Importance: medium This setting allows specifying an interval at which we will force an fsync of data written to the log. For example if this was set to 1 we would fsync after every message; if it were 5 we would fsync after every five messages. In general we recommend you not set this and use replication for durability and allow the operating system's background flush capabilities as it is more efficient. This setting can be overridden on a per-topic basis (see the per-topic configuration section ). flush.ms Type: long Default: 9223372036854775807 Valid Values: [0,... ] Server Default Property: log.flush.interval.ms Importance: medium This setting allows specifying a time interval at which we will force an fsync of data written to the log. For example if this was set to 1000 we would fsync after 1000 ms had passed. In general we recommend you not set this and use replication for durability and allow the operating system's background flush capabilities as it is more efficient. follower.replication.throttled.replicas Type: list Default: "" Valid Values: [partitionId]:[brokerId],[partitionId]:[brokerId],... Server Default Property: follower.replication.throttled.replicas Importance: medium A list of replicas for which log replication should be throttled on the follower side. The list should describe a set of replicas in the form [PartitionId]:[BrokerId],[PartitionId]:[BrokerId]:... or alternatively the wildcard '*' can be used to throttle all replicas for this topic. index.interval.bytes Type: int Default: 4096 (4 kibibytes) Valid Values: [0,... ] Server Default Property: log.index.interval.bytes Importance: medium This setting controls how frequently Kafka adds an index entry to its offset index. The default setting ensures that we index a message roughly every 4096 bytes. More indexing allows reads to jump closer to the exact position in the log but makes the index larger. You probably don't need to change this. leader.replication.throttled.replicas Type: list Default: "" Valid Values: [partitionId]:[brokerId],[partitionId]:[brokerId],... Server Default Property: leader.replication.throttled.replicas Importance: medium A list of replicas for which log replication should be throttled on the leader side. The list should describe a set of replicas in the form [PartitionId]:[BrokerId],[PartitionId]:[BrokerId]:... or alternatively the wildcard '*' can be used to throttle all replicas for this topic. max.compaction.lag.ms Type: long Default: 9223372036854775807 Valid Values: [1,... ] Server Default Property: log.cleaner.max.compaction.lag.ms Importance: medium The maximum time a message will remain ineligible for compaction in the log. Only applicable for logs that are being compacted. max.message.bytes Type: int Default: 1048588 Valid Values: [0,... ] Server Default Property: message.max.bytes Importance: medium The largest record batch size allowed by Kafka (after compression if compression is enabled). If this is increased and there are consumers older than 0.10.2, the consumers' fetch size must also be increased so that they can fetch record batches this large. In the latest message format version, records are always grouped into batches for efficiency. In message format versions, uncompressed records are not grouped into batches and this limit only applies to a single record in that case. message.format.version Type: string Default: 2.6-IV0 Valid Values: [0.8.0, 0.8.1, 0.8.2, 0.9.0, 0.10.0-IV0, 0.10.0-IV1, 0.10.1-IV0, 0.10.1-IV1, 0.10.1-IV2, 0.10.2-IV0, 0.11.0-IV0, 0.11.0-IV1, 0.11.0-IV2, 1.0-IV0, 1.1-IV0, 2.0-IV0, 2.0-IV1, 2.1-IV0, 2.1-IV1, 2.1-IV2, 2.2-IV0, 2.2-IV1, 2.3-IV0, 2.3-IV1, 2.4-IV0, 2.4-IV1, 2.5-IV0, 2.6-IV0] Server Default Property: log.message.format.version Importance: medium Specify the message format version the broker will use to append messages to the logs. The value should be a valid ApiVersion. Some examples are: 0.8.2, 0.9.0.0, 0.10.0, check ApiVersion for more details. By setting a particular message format version, the user is certifying that all the existing messages on disk are smaller or equal than the specified version. Setting this value incorrectly will cause consumers with older versions to break as they will receive messages with a format that they don't understand. message.timestamp.difference.max.ms Type: long Default: 9223372036854775807 Valid Values: [0,... ] Server Default Property: log.message.timestamp.difference.max.ms Importance: medium The maximum difference allowed between the timestamp when a broker receives a message and the timestamp specified in the message. If message.timestamp.type=CreateTime, a message will be rejected if the difference in timestamp exceeds this threshold. This configuration is ignored if message.timestamp.type=LogAppendTime. message.timestamp.type Type: string Default: CreateTime Valid Values: [CreateTime, LogAppendTime] Server Default Property: log.message.timestamp.type Importance: medium Define whether the timestamp in the message is message create time or log append time. The value should be either CreateTime or LogAppendTime . min.cleanable.dirty.ratio Type: double Default: 0.5 Valid Values: [0,... ,1] Server Default Property: log.cleaner.min.cleanable.ratio Importance: medium This configuration controls how frequently the log compactor will attempt to clean the log (assuming log compaction is enabled). By default we will avoid cleaning a log where more than 50% of the log has been compacted. This ratio bounds the maximum space wasted in the log by duplicates (at 50% at most 50% of the log could be duplicates). A higher ratio will mean fewer, more efficient cleanings but will mean more wasted space in the log. If the max.compaction.lag.ms or the min.compaction.lag.ms configurations are also specified, then the log compactor considers the log to be eligible for compaction as soon as either: (i) the dirty ratio threshold has been met and the log has had dirty (uncompacted) records for at least the min.compaction.lag.ms duration, or (ii) if the log has had dirty (uncompacted) records for at most the max.compaction.lag.ms period. min.compaction.lag.ms Type: long Default: 0 Valid Values: [0,... ] Server Default Property: log.cleaner.min.compaction.lag.ms Importance: medium The minimum time a message will remain uncompacted in the log. Only applicable for logs that are being compacted. min.insync.replicas Type: int Default: 1 Valid Values: [1,... ] Server Default Property: min.insync.replicas Importance: medium When a producer sets acks to "all" (or "-1"), this configuration specifies the minimum number of replicas that must acknowledge a write for the write to be considered successful. If this minimum cannot be met, then the producer will raise an exception (either NotEnoughReplicas or NotEnoughReplicasAfterAppend). When used together, min.insync.replicas and acks allow you to enforce greater durability guarantees. A typical scenario would be to create a topic with a replication factor of 3, set min.insync.replicas to 2, and produce with acks of "all". This will ensure that the producer raises an exception if a majority of replicas do not receive a write. preallocate Type: boolean Default: false Server Default Property: log.preallocate Importance: medium True if we should preallocate the file on disk when creating a new log segment. retention.bytes Type: long Default: -1 Server Default Property: log.retention.bytes Importance: medium This configuration controls the maximum size a partition (which consists of log segments) can grow to before we will discard old log segments to free up space if we are using the "delete" retention policy. By default there is no size limit only a time limit. Since this limit is enforced at the partition level, multiply it by the number of partitions to compute the topic retention in bytes. retention.ms Type: long Default: 604800000 (7 days) Valid Values: [-1,... ] Server Default Property: log.retention.ms Importance: medium This configuration controls the maximum time we will retain a log before we will discard old log segments to free up space if we are using the "delete" retention policy. This represents an SLA on how soon consumers must read their data. If set to -1, no time limit is applied. segment.bytes Type: int Default: 1073741824 (1 gibibyte) Valid Values: [14,... ] Server Default Property: log.segment.bytes Importance: medium This configuration controls the segment file size for the log. Retention and cleaning is always done a file at a time so a larger segment size means fewer files but less granular control over retention. segment.index.bytes Type: int Default: 10485760 (10 mebibytes) Valid Values: [0,... ] Server Default Property: log.index.size.max.bytes Importance: medium This configuration controls the size of the index that maps offsets to file positions. We preallocate this index file and shrink it only after log rolls. You generally should not need to change this setting. segment.jitter.ms Type: long Default: 0 Valid Values: [0,... ] Server Default Property: log.roll.jitter.ms Importance: medium The maximum random jitter subtracted from the scheduled segment roll time to avoid thundering herds of segment rolling. segment.ms Type: long Default: 604800000 (7 days) Valid Values: [1,... ] Server Default Property: log.roll.ms Importance: medium This configuration controls the period of time after which Kafka will force the log to roll even if the segment file isn't full to ensure that retention can delete or compact old data. unclean.leader.election.enable Type: boolean Default: false Server Default Property: unclean.leader.election.enable Importance: medium Indicates whether to enable replicas not in the ISR set to be elected as leader as a last resort, even though doing so may result in data loss. message.downconversion.enable Type: boolean Default: true Server Default Property: log.message.downconversion.enable Importance: low This configuration controls whether down-conversion of message formats is enabled to satisfy consume requests. When set to false , broker will not perform down-conversion for consumers expecting an older message format. The broker responds with UNSUPPORTED_VERSION error for consume requests from such older clients. This configurationdoes not apply to any message format conversion that might be required for replication to followers.

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