Kafka consumer offset example Let’s say one consumer has read five messages from a partition. The numbering Apr 2, 2024 · Example: auto. sh --bootstrap-server localhost:9092 --topic test-topic --partition 0 --offset 0 Message2 Message5 Here, the –partition 0 and –offset 0 options specify the partition and the offset to consume from. Kafka Consumer — Auto Offset Commit Diagram. Mar 9, 2018 · Since kafka 0. Dec 18, 2023 · In this example, we’re focusing on a Kafka topic that has three partitions: partitions zero, one, and two. Offsets are integers starting from zero that increment by one as the message gets stored. serialization. 0. reset config kicks in ONLY if your consumer group does not have a valid offset committed somewhere (2 supported offset storages now are Kafka and Zookeeper), and it also depends on what sort of consumer you use. If you wanted to replay messages from a given offset, you could use consumer. ms=5000 and enable. Offsets are the key to ordered, reliable data processing in Kafka – but when they get lost or corrupted, things can go downhill fast! In this post, I‘ll provide an in-depth guide to Kafka‘s auto […] On each poll, consumer will try to use the last consumed offset as the starting offset and fetch sequentially. And Confluent also mentioned: "If the consumer crashes or is shut down, its partitions will be re-assigned to another member, which will begin consumption from the last committed offset of each partition" Jun 21, 2020 · Example. It essentially acts as a marker indicating the last consumed message, ensuring that consumers know where to resume processing. A group ID value for consumer group coordination. And then the next message to be written is going to be message number 12, offset number 12. Oct 9, 2024 · Learn about how Kafka consumer offset works and how it identifies the position of an event record in a partition. Docker Compose is used for building a single node Kafka cluster and running multiple consumer instances. For our example, we’ll use String keys and values and the following deserializer: org. Blog post: Apache Kafka Data Access Semantics: Consumers and Membership; Free course: Apache Kafka 101 Mar 17, 2024 · Here, Kafka, with the help of offsets, keeps track of the messages that consumers read. Confluent develops and maintains confluent-kafka-dotnet, a . Imagine you have a kafka topic with a single partition, and a consumer group with two consumers, Consumer-A and Consumer-B, is reading messages. The Kafka consumer offset allows Aug 29, 2024 · Now, we’ll read messages from a specific offset. The minimum buffered bytes defines what “enough” is. To see examples of consumers written in various languages, see Kafka Client Examples for Confluent Platform. common. reset” that indicates what should be done when there’s no initial offset in Kafka or if the current offset doesn’t exist anymore on the server. Whether processing billions of real-time events, syncing datasets across regions, or building planet-scale stream processors – it‘s crucial […] Jan 21, 2016 · When Apache Kafka® was originally created, it shipped with a Scala producer and consumer client. Kafka acknowledgment description. Docs; Help; GitHub › Examples The two different variants of the seek methods provide a way to seek to an arbitrary offset. Apr 24, 2025 · Your All-in-One Learning Portal: GeeksforGeeks is a comprehensive educational platform that empowers learners across domains-spanning computer science and programming, school education, upskilling, commerce, software tools, competitive exams, and more. It helps consumers keep track of their progress like how many messages each consumer has already consumed Apache Kafka offsets play a crucial role in managing message consumption within Kafka topics. Offset Management with Example. Run Kafka server as described here. Feb 4, 2025 · How to Reset Offset Example 1: Resetting Offset to Earliest for a Consumer Group. Keeping track of the offset, or position, is important for nearly all Kafka use cases and can be an absolute necessity in certain instances, such as financial services. In this article, we are going to discuss the step-by-step implementation of how to Create an Apache Kafka Consumer using Java. As long as all Sep 10, 2019 · In this Kafka pub sub example you will learn, • Kafka producer components (producer api, serializer and partition strategy) • Kafka producer architecture • Kafka producer send method (fire and forget, sync and async types) • Kafka producer config (connection properties) example • Kafka producer example • Kafka consumer examplePrerequisite - refer my previous post on Apache Kafka Jul 24, 2021 · Current Offset: The current offset is a reference to the most recent record that Kafka has already provided to a consumer. consumers-count. You can reset the offset to the earliest: kafka-consumer-groups. auto. Over time we came to realize many of the limitations of these APIs. component. StringDeserializer Oct 19, 2024 · A Kafka consumer offset is a unique, steadily increasing number that marks the position of an event record in a partition. Example config Offset info before consumer loop, Committed: 4, current position 4 Sending message topic: Nov 14, 2024 · 3. The earliest and latest values for the auto. sh: $ kafka-console-consumer. For Hello World examples of Kafka clients in various programming languages including Java, see Code Examples for Apache Kafka. This function provides access to the current offset (the current position returned by the consumer, which is the next offset to be fetched). Dec 27, 2023 · Dear reader, welcome to my comprehensive guide on building Kafka consumers in Python! Given Kafka‘s meteoric rise as the central nervous system for modern data architectures, I‘m thrilled to help you master one of its fundamental pieces. Nov 26, 2023 · Confluent Kafka. 9 Apache Zookeeper was used for managing the offsets of the consumer group. Examples. Jan 18, 2018 · When a consumer joins a consumer group it will fetch the last committed offset so it will restart to read from 5, 6, 7 if before crashing it committed the latest offset (so 4). kafka-consumer-groups. apache. When a consumer fails the load is automatically distributed to other members of the group. One of its most powerful features is the ability to control the position of a consumer in a topic’s partition using the seek method. kafka. How does a consumer commit an offset? It produces a message to Kafka, to a special __consumer_offsets topic, with the committed offset for each partition. Step by step guide to realize a Kafka Consumer is provided for understanding. For example, a consumer which is at position 5 has consumed records with offsets 0 through 4 and will next receive the record with offset 5. Messages Jun 21, 2020 · Kafka consumer will auto commit the offset of the last message received in response to its poll() call. This allows scaling out consumers with the guarantee of only-once message delivery. Nov 27, 2024 · In Kafka, a consumer offset represents the position of a consumer within a partition of a topic. This guide explores the different types of Kafka offsets and their significance in building robust data processing pipelines. What is a Kafka Consumer ? A Consumer is an application that reads data from Kafka Topics. Example 1: Basic Offset Tracking in a Consumer Group. reset=latest Apache Kafka Tutorial – Learn about Apache Kafka Consumer with Example Java Application working as a Kafka consumer. We call the action of updating the current position in the partition a commit. assign() API may help you. The number of consumers that connect to kafka server. Each consumer is run on a separate thread that retrieves and process the incoming data. reset property is used when a consumer starts but there is no committed offset for the assigned partition. These APIs are also helpful to replay data from a specific offset. Example: kafka-consumer-groups --bootstrap-server <kafka_broker> --group Mar 24, 2017 · "For an existing group ID, the initial offset is the current offset for that group ID". Consider a scenario where an analytics system needs to reprocess all past data from a Kafka topic. id configuration setting. Kafka brokers use an internal topic named __consumer_offsets that keeps track of what messages a given consumer group last successfully processed. seek(partition, offset). This can be achieved by using the commitSync() or Instead, it allows consumers to use Kafka to track their position (offset) in each partition. 0 you can use the script kafka-consumer-groups. etc, maybe all the way up to 11. In this tutorial, you'll learn how to use the Apache Kafka console consumer to quickly debug issues by reading from a specific offset and/or These properties determine the consumer group to which the consumer belongs, control whether the consumer automatically commits offsets, determine how the consumer handles starting from an unknown offset, control the interval at which the consumer sends heartbeats to the group coordinator, and dictate the maximum number of records that the Jan 8, 2024 · Kafka uses the committed offset to keep track of the last position read from a topic. Kafka has two offset management strategies Defining Kafka Consumer Offset. interval. In such cases, Kafka provides a property “auto. offset. Nov 12, 2023 · Hey there! If you‘re building applications using Apache Kafka, you‘ve likely dealt with the challenge of managing consumer message offsets. Feb 17, 2023 · A kafka offset is a unique identifier for each message within a kafka partition. Message delivery guarantees with Kafka offsets By default, Kafka pulls in a micro-batch of messages and commits the offset at periodic intervals. reset=earliest; start from the end (awaiting new messages) if auto. commit=true will commit. The consumer polls the Kafka brokers to check if there is enough data to receive. As a result of the current offset, the consumer does not receive the same Aug 10, 2022 · As we’ve seen from the previous example, the data received by the consumer isn’t exactly “real time”. Then, based on configuration, Kafka marks the offset till 4 as committed Nov 27, 2024 · If a consumer fails after processing offset 3 in Partition 0, the next consumer (or restart) will resume from offset 4. 9, it’s not zookeeper anymore that store the information about what were the offset consumed by each groupid on a topic by partition. sh --bootstrap-server kafka-host:9092 --group my-group --reset-offsets --to-earliest --all-topics --execute Other options listed in the KIP-122: Add Reset Consumer Group Offsets tooling Apr 22, 2023 · Implementation of Kafka listener with manual acknowledgment. NET library that provides a high-level producer, consumer, and AdminClient compatible with all Apache Kafka® brokers camel. properties for manual offset commit. When a consumer issues a request, it specifies a log offset, and then receives a chunk of log that starts with the offset position specified. Integer. In other words, it’s the starting point for itself and other consumers to read events in subsequent rounds. Create a Consumer. How to deserialize the key and value of events. For example, CURRENT . For example, […] Dec 13, 2022 · Setting enable. Each consumer in the group keeps its own offset for each partition to track progress. While this feature allows applications to process records asynchronously, it should be understood that it increases the possibility of duplicate deliveries after a failure. This offset acts as a unique identifier of a record within that partition, and also denotes the position of the consumer in the partition. Consumer groups __must have__ unique group ids within the cluster, from a kafka broker perspective. sh --bootstrap-server kafka-broker:9092 --group analytics-consumer --reset-offsets --to-earliest Apr 24, 2025 · And in case of broker failures, the consumers know how to recover and this is again a good property of Apache Kafka. Messages sent to a Kafka topic are distributed across these partitions. The committed offset is the position in the topic to which a consumer acknowledges having successfully processed. For example, if we have a configuration like this: Consumer groups allow a group of machines or processes to coordinate access to a list of topics, distributing the load among the consumers. 2. Jan 10, 2023 · We will discuss how to configure the Kafka consumer to seek offsets by timestamp where topic partitions are dynamically assigned by subscription. They provide a way to track the position of a consumer within a partition of a topic. Resources for additional reading. The “auto. Example In case you are looking to read specific messages from specific partitions, the . May 11, 2024 · A new consumer group won’t have any offset associated with it. Kafka maintains a numerical offset for each record in a partition. Let's build a simple application that uses a KafkaConsumer to read records from Kafka. Mar 10, 2024 · Creating a Kafka Consumer: — Kafka consumers track their position (offset) offsets stored in the database when partitions are assigned or when the consumer starts. camel. Oct 18, 2022 · So if we take this example of a Kafka Topic with 3 partitions then if we look at Partition 0, it will have the message with Offset 0, then the message with Offset 1, 2, 3. At a minimum, the Consumer needs to know: How to find the Kafka broker(s). sh Example from this answer. The last consumed offset can be manually set through seek() or automatically set as the last committed offset for the subscribed list of partitions. The method that takes a Function as an argument to compute the offset was added in version 3. How to read from a specific offset and partition with the Apache Kafka ® console consumer Setup. 2 of the framework. It subscribes to one or more topics in the Kafka cluster KafkaJS 2. Sep 4, 2015 · The auto. As we know, each message in a Kafka topic has a partition ID and an offset ID attached to it. The consumer will be paused (no new records delivered) until all the offsets for the previous poll have been committed. Nov 25, 2024 · In the above code, seekToBeginning moves the offset of the consumer to the beginning of the partition and replays all messages. commit to false takes Kafka consumers out of the “autopilot mode” and it’s up to the application to commit the offsets. Step by Step Implementation Apr 22, 2015 · Since kafka 0. This tool allows you to reset or change the offset of a consumer group to a specific value. Kafka now store this information on a topic Kafka maintains a numerical offset for each record in a partition. The following picture shows multiple producers and consumers working together with Kafka: 4. A consumer group will contain one or more consumers. You are confirming record arrivals, and you'd like to read from a specific offset in a topic partition. I’m already sharing this information, but let’s go over it again. Here's how offsets work in this scenario: For versions less than 0. 1. Only one consumer of a consumer group will receive the message. Feb 21, 2025 · How Do I Change the Offset of a Consumer Group in Kafka? To change the offset of a consumer group, you can use Kafka's built-in tooling, such as the Kafka-consumer-groups command. Now data for the consumers is going to be read in order within each partition. Add application. commit. 11. . Dec 26, 2024 · Apache Kafka is a distributed event-streaming platform used to handle real-time data. Offset management is the mechanism, which tracks the number of records that have been consumed from a partition of a topic for a particular consumer group. Feb 6, 2025 · Consumers are part of a Consumer Group that Kafka identifies by a simple name. reset parameter and either: start from the first record available if auto. Using Kafka CLI to reset offsets Sep 12, 2020 · If there is no offset stored for a consumer group (it is the first poll or previously committed offset expired) then your consumer will look at the auto. This gives the consumer control over what it consumes, and it can specify an offset to reconsume data if needed. 1 Kafka maintains a numerical offset for each record in a partition. Real-Time Examples of Kafka Offset Management. We start a consumer using kafka-console-consumer. 4. What are Kafka Offsets? In case of consumer termination and restart, the Kafka offset ensures the consumer can resume the correct message. The delay in millis seconds to wait before trying again to create the kafka consumer (kafka Apr 9, 2022 · Every Kafka consumer belongs to a consumer group, grouped together by the consumer’s group. create-consumer-backoff-interval. There are required properties needed to create a Kafka Consumer. The consumer offset is a way of tracking the sequential order in which messages are received by Kafka topics. reset” property accepts the following values: Jan 10, 2024 · Auto Offset Reset: the position in the Kafka log to start reading data when there is no initial offset Key/Value Deserializers: the deserializer classes for the keys and values. seek() and . kwyeff upjdop pab vsfoqb juul dukyn ezolxqc pekshpo fvyc rgoref