Log¶

Creating Instance¶

Log takes the following to be created:

• Directory
• LogConfig
• LogSegments
• logStartOffset
• recoveryPoint
• LogOffsetMetadata
• Scheduler
• BrokerTopicStats
• Time
• producerIdExpirationCheckIntervalMs
• TopicPartition
• Optional LeaderEpochFileCache
• ProducerStateManager
• LogDirFailureChannel
• Optional Topic ID
• keepPartitionMetadataFile

Log is created using apply utility.

Creating Log¶

apply(
  dir: File,
  config: LogConfig,
  logStartOffset: Long,
  recoveryPoint: Long,
  scheduler: Scheduler,
  brokerTopicStats: BrokerTopicStats,
  time: Time = Time.SYSTEM,
  maxProducerIdExpirationMs: Int,
  producerIdExpirationCheckIntervalMs: Int,
  logDirFailureChannel: LogDirFailureChannel,
  lastShutdownClean: Boolean = true,
  topicId: Option[Uuid],
  keepPartitionMetadataFile: Boolean): Log

apply...FIXME

apply is used when:

• LogManager is requested to loadLog and getOrCreateLog
• KafkaMetadataLog is requested to apply

Reading Messages¶

read(
  startOffset: Long,
  maxLength: Int,
  isolation: FetchIsolation,
  minOneMessage: Boolean): FetchDataInfo

read prints out the following TRACE message to the logs:

Reading maximum [maxLength] bytes at offset [startOffset] from log with total length [size] bytes

read...FIXME

read requests the LogSegment to read messages.

read...FIXME

read is used when:

• Partition is requested to readRecords
• GroupMetadataManager is requested to doLoadGroupsAndOffsets
• TransactionStateManager is requested to loadTransactionMetadata
• Log is requested to convertToOffsetMetadataOrThrow
• KafkaMetadataLog is requested to read

Logging¶

Enable ALL logging level for kafka.log.Log logger to see what happens inside.

Add the following line to log4j.properties:

log4j.logger.kafka.log.Log=ALL

Refer to Logging.