High-water mark
A high-water mark is a maximum observed value or configured threshold that bounds, tracks, or controls progress, storage, or processing.
Apache Kafka in Action
A high water mark is the highest offset in a Kafka partition whose record is available for consumption because the required replicas have received it.
- How it is used
- Uses replica progress to determine which Kafka records are committed and available to consumers.
- How deep it goes
- Explains HWM calculation through LEO and ISR fetches, then traces lag effects without detailing broker persistence internals.
- Examples
- Illustrates leader and follower offsets, a lagging ISR, HWM advancement, and blocked consumption when the minimum ISR is unavailable.
- What you can do after
- Diagnose/debug with it by relating consumer stalls and delayed visibility to ISR lag and minimum-replica settings.
Kafka Streams in Action, Second Edition
A high-water mark is the greatest partition offset replicated to all in-sync replicas and made accessible to consumers.
- How it is used
- Limits consumer visibility to records replicated across all in-sync replicas.
- How deep it goes
- Defines the replication boundary, works through offsets 8–10, and contrasts it with the transactional last stable offset.
- Examples
- Uses offsets 8–10 awaiting replication and contrasts nontransactional polling with read_committed polling.
- What you can do after
- Configure consumers with read_committed while distinguishing replication durability from transactional visibility.
Read how Kafka Streams in Action, Second Edition explains high-water mark →
Related concepts
- offsetmeasures · An offset is a position or displacement measured relative to a reference point, such as within an ordered sequence, memory region, or layout.
- in-sync replicaused by · An in-sync replica is a Kafka partition replica sufficiently caught up with its leader to remain eligible for failover.
- Reactconfigured by · React is an open-source JavaScript library for building user interfaces from declarative, reusable components.
- min.insync.replicasconfigured by · min.insync.replicas is a Kafka setting specifying the minimum number of in-sync replicas that must acknowledge a write for it to succeed.
- clientconfigures · A client is a person, organization, device, or software component that receives or uses a product, service, resource, or functionality provided by another entity.
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