Kafka streams processor context An incoming message, from an input topic, can be acknowledged only when it has been processed and its result message has been produced and stored in a Kafka output topic. Jan 15, 2018 · While using Processor API of Kafka Streams, I use something like this: context. Kafka Streams application architecture overview Use cases for Kafka Streams. Stream-time is tracked on a per-task basis and is preserved across restarts and during task migration. withTimestamp()). I read about using Processor API, using Schedule a periodic operation for processors. Apr 25, 2018 · // Creating an in-memory key-value store: // here, we create a `KeyValueStore<String, Long>` named "inmemory-counts". NOTE: Only advanced if messages arrive If it is triggered while processing a record generated not from the source processor (for example, if this method is invoked from the punctuate call), timestamp is defined as the current task's stream time, which is defined as the smallest among all its input stream partition timestamps. I am not finding a clear way of doing this in processorAPI. And of course, the parent may forward the same object to multiple children, and the child may forward it to grandchildren, etc. You run these applications on client machines at the periphery of a Kafka cluster. Jul 21, 2024 · ProcessorContext: This interface provides metadata related to the application, such as applicationId, taskId, and stateDir, as well as metadata of the currently processed record. In Kafka Streams app I want to add current temperature in the target city to the record. Kafka Streams processors are not thread-safe, so a processor scope is @jakarta. Oct 25, 2017 · The usage of ProcessorContext is somewhat limited and you cannot call each method is provides at arbitrary times. Copy of processor. It is provided for you to take any graceful shutdown measures before exiting the application. context. 4, these transformers are deprecated in favor of the new processor API. It represents a processing step in a topology, i. Processor interface has the init method. The tests for this class (org. So how can headers help in this regard? These are the good old signatures of the Kafka Serializer and Deserializer: Oct 15, 2023 · Kafka Streams support a set of commonly used data transformations such as filtering, data mapping, branching, etc that initializes the processor with state store and processor context. However, most applications should instead favor safety. It's working fine in terms of Kafka flow but the tracing support seems incomplete (baggage values updated in a processor are not propagated) when using this method. process() providing it with an appropriate Processor implementation. If it is triggered while processing a record generated not from the source processor (for example, if this method is invoked from the punctuate call), timestamp is defined as the current task's stream time, which is defined as the smallest among all its input stream partition timestamps. In productions settings, Kafka Streams applications are most likely distributed based on the number of partitions. Kafka streams application does not consume messages. Is there anyway to use context. My streaming app flow is . Dependent by default. Essentially, the processor topology can be considered as a directed acyclic graph. 1. Feb 18, 2025 · Kafka Streams is a powerful library that allows developers to build applications that process data in real-time using Kafka. state. Java 8 stream and incoming data (Kafka) 1. Apache Kafka Toggle navigation. There are close links between Kafka Streams and Kafka in the context of parallelism: Each stream partition is a totally ordered sequence of data records and maps to a Kafka topic partition. Feb 24, 2019 · using kafka-streams to conditionally sort a json input stream. ValidateProcessor. e. With the Processor API, you can define arbitrary stream processors that process one received record at a time, and connect these processors with their associated state stores to compose the processor topology that represents a customized processing logic. Kafka Streams 概念 二. It won't continue processing. kafka:kafka-streams-test-utils:3. To clarify what Matthias said: Yes, the Processor API in Kafka Streams gives you access to record metadata such as topic name, partition number, offset, etc. We need to process the records that are being pushed to the outerjoin topic by the outer join operation. As we have mentioned above, the computational logic of a Kafka Streams application is defined as a processor topology. Processor Contract — Stream Processing Node AbstractProcessor — Base for Stream Processors ProcessorContext Kafka Streams Execution Engine; Jun 14, 2019 · But, let’s get started. 0 in favor of org. Kafka Streams offers powerful event stream processing capabilities that make it ideal for a wide range of use cases, including fraud detection, data cleansing, workflow automation, event-driven communication, enriching data streams, and real-time analytics. Oct 24, 2023 · Since Kafka Streams 3. While Kafka Streams commits on a regular (configurable) interval, you can request intermediate commits when you use it. , it can be considered a high-watermark. May 31, 2018 · A Kafka Streams processing application defines its computational logic through one or more processor topologies, where a processor topology is a graph of stream processors (nodes) that are Apr 7, 2021 · I'm trying to write a Kafka stream processor using Spring boot but it's not getting invoked when messages are produced into the topic. Nov 19, 2019 · I have a kafka streams application using processor API. 이 Topology는 2개 이상의 하위 토폴로지에 의해 형성될 수 있다. Mar 14, 2025 · In Kafka Streams, the ProcessorSupplier interface plays a crucial role in defining how processors are instantiated and managed within a stream processing topology. Return the current stream-time in milliseconds. It provides a high-level API for building real-time stream processing applications. Dedicated local streams across North America, Europe, and Asia-Pacific will explore the latest Java AI models to develop LLM apps and agents, learning best practices for app modernization with AI-assisted dev tools, learning the latest in Java frameworks Feb 15, 2019 · 本文将从以下三个方面全面介绍Kafka Streams 一. Kafka Streams 使用 三. May 1, 2019 · In Kafka Stream API, is it possible to forward more than one record at once to different child processors ? For an example, let say we have a parent processor called Processor-Parent and two child processors, Child-1, Child-2. forward(key,value) context. Mar 15, 2019 · I think, you misunderstood the transform API. if(result. Oct 24, 2018 · Kafka Streams will assign the partitions to the task such that the partitioning is preserved. Kafka Streams WordCount . Mar 4, 2020 · I was able to access the store from a transform. It allows Some programs may opt to make use of this mutability for high performance, in which case the input record may be mutated and then forwarded by each Processor. Apache Kafka: A Distributed Streaming Platform. offset() method that returns the value, but I'm using KStream instead of the Processor, and I couldn't find a method that returns the same thing. Processor that has been deprecated since version 3. Kafka Streams allows developers to process and analyze data streams in real-time, enabling them to derive valuable insights and perform various computations on the data. It turns out, the streambuilder sequence of order matters. Note that the forwarded FixedKeyRecord is shared between the parent and child processors. I moved my lines of code to create the KTable first with materialized store, then create the other stream processor that uses the transform to access the store. The first punctuation will be triggered by the first record that is processed. ProcessorContext. The DSL in Kafka Streams does not give you access. The init() method passes in a ProcessorContext instance, which provides access to the metadata of the currently processed Apr 17, 2020 · I have below kafka stream code public class KafkaStreamHandler implements Processor&lt;String, String&gt;{ private ProcessorContext context; @Override public void init( If it is triggered while processing a record generated not from the source processor (for example, if this method is invoked from the punctuate call), timestamp is defined as the current task's stream time, which is defined as the smallest among all its input stream partition timestamps. schedule() in init() method). When Processor-Parent receives a record to process, I would like to do the following. In the init method, store a reference to the Processor context, get a reference to the state store by name, and store it in the storeName variable declared above. Let's say the record has city_id and some other fields. xml. apache. it is used to transform data. I want to access record headers, partition no etc in my Kafka streams application. Temperature<->City pairs are stored in eg. May 8, 2019 · I have records that are processed with Kafka Streams (using Processor API). api. PunctuationType. enterprise. @Override. Therefore, you should be mindful of mutability. What I don't understand here is: MockProcessorContext is a mock of ProcessorContext for users to test their Processor, Transformer, and ValueTransformer implementations. When the framework is done with the processor, Processor. close() will be called on it; the framework may later re-use the processor by calling #init() again. Kafka streams using context forward from processor called in dsl api. Related to that, Kafka Streams applications with the Processor API are typically built as follows: Add source node(s) Add N number of processors, child nodes of the source node(s) (child nodes can have any number of Dec 5, 2019 · Before the process method call, the correct record context is created by the caller ProcessorContext implementation, and it forwards the call to the custom processor, but the context held by the custom processor is not set. Kafka Streams provides a Processor API that we can use to write custom logic for record Jan 27, 2022 · I am using Kafka 2. Sometimes you'll find that the external data is best brought into Kafka itself (e. Kafka Streams application stops working after no message have been read for a while. What might be the reason for the init method passing in a ProcessContext where the record context is not set? Oct 24, 2016 · For one of my Kafka streams apps, I need to use the features of both DSL and Processor API. A “higher-level” stream DSL that would cover most processor implementation needs. Processor topology is the blueprint of Kafka Stream operations on one or more event streams. A stream processor is a node in the processor topology that represents a single processing step. Kafka Streams: Punctuate Nov 25, 2016 · My problem is: the org. streams. Related. MockProcessorContext is a mock of ProcessorContext for users to test their Processor, Transformer, and ValueTransformer implementations. More specifically, I noticed that the record's offset is always 0 when using the Processor from the latter Kafka Streams also gives access to a low level Processor API. Stream-time is the maximum observed record timestamp so far (including the currently processed record), i. Stores; // Note: The `Stores` factory returns a supplier for the state store, // because that's what you typically need to pass Mar 9, 2021 · Kafka Streams uses the concepts of stream partitions and stream tasks as logical units of its parallelism model. g. ProcessorContext Dec 8, 2023 · I have a kafka stream application (written in java springboot), which has let say 3 processors. They MockProcessorContext is a mock of ProcessorContext for users to test their Processor, Transformer, and ValueTransformer implementations. Then use the processor context to schedule a punctuation that fires every 30 seconds, based on stream time. Standard operations such as map or filter, joins, and aggregations are examples of stream processors that are available in Kafka Streams out of the box. Forward a record to all child processors. Kafka Streams는 특정 역할을 가진 노드를 연결하여 그래프 구조를 구축하고 Topology를 형성하고 동작한다. A “lower-level” processor that providea API’s for data-processing, composable processing and local state storage. StreamsException: Processor KSTREAM-TRANSFORM-0000000002 has no access to StateStore my-store as the store is not connected to the processor Cannot get custom store connected to a Transformer with Spring Cloud Stream Binder Kafka 3. Kafka Streams 提供的 Processor API 是一个更底层的 API，允许对流处理任务进行细粒度的可控操作。主要组件包括： Processor：流处理逻辑单元，可以处理输入、更新状态，以及生成输出。 Transformer：用于转换现有数据并可能保留处理状态。 A stream processor is a node in the processor topology as shown in the diagram of section Processor Topology. Sep 17, 2018 · A side note to your question, is that calling external APIs from a streams processor is not always the best pattern. java. Kafka Streams 概念. You will also debug your stream processor using the Eclipse debug tool. Initialize this processor with the given context. This marks a start of a series covering the new Kafka processor client, with this post covering the “lower-level” processor functionality. It simplifies the process of working with data streams by providing a high-level abstraction for stream processing. ProcessorContext class exposes an . Building Streams Applications with the Processor API. Processor API. Add kafka-streams-test-utils to your project dependencies. Postgres. CDC from databases, mainframes,etc) as its own topic, and then easily joined within the stream processing itself. import org. Initializing the context: private class PoisonMessageTransformer implements Dec 13, 2020 · Periodic NPE In Kafka Streams Processor Context. 1 Kafka Streams Kafka Streams。Apache Kafka开源项目的一个组成部分。是一个功能强大，易于使用的库。用于在Kafka上构建高可分布式、拓展性，容错的应用程序。 1. 2 Kafka Streams特点 1．功能强大 （1） Forward a record to all child processors. Sep 28, 2020 · Next, we will add the state store and processor code. Kafka Streams 9. Jan 8, 2024 · An important concept of Kafka Streams is that of processor topology. commit() Actually, what I'm doing here is sending forward a state from state store to sink every minute (using context. Jan 31, 2024 · Kafka Streams is a versatile library for building scalable, high-throughput, and fault-tolerant real-time stream processing applications. The framework ensures this is called once per processor when the topology that contains it is initialized. isSuccessful()) { context(). Note that the forwarded Record is shared between the parent and child processors. In this part, you will test the stream processor using kafka-streams-test-utils and JUnit 5. The processor API, although very powerful and gives the ability to control things in a much lower level, is imperative in nature. With the Processor API, you can define arbitrary stream processors that processes one received record at a time, and connect these processors with their associated state stores to compose the processor topology. 2. In turn, the Kafka Streams engine was attempting to create multiple processor instances, which I have no doubt created a multi-threaded dumpster fire. The kafka-streams-examples GitHub repo is a curated repo with examples that demonstrate the use of Kafka Streams DSL, the low-level Processor API, Java 8 lambda expressions, reading and writing Avro data, and implementing unit tests with TopologyTestDriver and end-to-end integration tests using embedded Kafka clusters. If you end up here, the following is a unit test working using org. In this graph, nodes are categorized into source, processor, and sink nodes, whereas the edges Dec 25, 2022 · In advanced Kafka streams applications some sort of batching/suppression is routinely used to control data that is pushed out to downstream services. Schedule a periodic operation for processors. Apr 27, 2019 · The proposed solutions seem to be based on org. You will recall the Kafka Streams topology from the Basic Operations module. A processor may call this method during initialization, processing, initialization, or processing to schedule a periodic callback — called a punctuation — to Punctuator. process(() -> new WindowAggregatorProcessor(storeName), storeName); 9. Nov 21, 2024 · I'm experiencing two issues with Kafka Streams' processValues() and suppress operations: Getting NPE when using processValues(): @Bean public Function<KStream<;String, String&gt;, KStream&lt; Aug 2, 2024 · Caused by: org. 0. kafka. public void process(String key, String value) { Object result = //validation logic. Within the Transformer, the state is obtained via the ProcessorContext. I have the following topology which uses processValues() method to combine streams DSL with Processor Api. Kafka Streams binder for Spring Cloud Stream, allows you to use either the high level DSL or mixing both the DSL and the processor API. 6 with spring cloud stream kafka-streams binder. It will be beneficial to both, people who work with Kafka Streams, and people who are integrating Kafka Streams with their Spring applications. forward("error",Object) Processors may be invoked to process a source record from an input topic, to run a scheduled punctuation (see schedule(Duration, PunctuationType, Punctuator)), or because a parent processor called forward(Record). . I have the following producer that works fine with the topic n (new class) org. In second processor, I want to call a rest api in asynchronous manner and when response comes, I want Sep 21, 2023 · Kafka Streams, on the other hand, is a powerful library built on top of Apache Kafka. stream. Jan 19, 2018 · It worth highlighting that record's metadata should be extracted from the ProcessorContext under the org. Open pom. In other words, Kafka Streams applications don’t run inside the Kafka brokers (servers) or the Kafka cluster. 7. Thus, it depend how you use it -- in general, you can pass it around as you wish (it will always be the same object throughout the live time of the processor). I’ll be building my custom kafka streams aggregator using Processor API on top of Spring Framework with Spring Cloud (why? Because I can!). I have a wall clock based punctuate that checks for stale entries in local statestore and deletes them and publishes messages on a kafa topic Schedule a periodic operation for processors. all(). MockProcessorContextTest) include several behavioral tests that serve as example usage. Anybody knows how to extract the consumer value for each row from a KStream? Thanks in advance. By following this guide, you’ve learned the basics and are well on your way to creating sophisticated stream processing applications with Kafka Streams. KStream<String, SecurityCommand&gt; securityCommands = The following examples show how to use org. forward(key, value); }else { context. Sep 5, 2023 · Kafka Streams is a popular stream processing library and framework that is part of the Apache Kafka ecosystem. As per the definition,transform each record of the input stream into zero or more records in the output stream. 7. 一. One of Jan 28, 2018 · Periodic NPE In Kafka Streams Processor Context. In particular, some Kafka Streams DSL operators set result record timestamps explicitly, to guarantee deterministic results. processor and not the org. There are close links between Kafka Streams and Kafka in the context of parallelism: First Kafka stream analyse the applications processor or topology (user defined kafka stream application) and then scaled it by breaking it into Note, that an upstream Processor might have set a new timestamp by calling forward(, To. topic(). Step 2: Add the Kafka Streams processor. Processor and there is no access to headers via context anymore. To get an access to ProcessorContext use KStream. forward() when calling a processor from the dsl? NOTE: I need to use a processor instead of a transform as I have custom logic on when to forward records down stream. The Processor API allows developers to define and connect custom processors and to interact with state stores. forward. Click the Dependencies tab, and then click the Add button. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. STREAM_TIME — uses "stream time", which is advanced by the processing of messages in accordance with the timestamp as extracted by the TimestampExtractor in use. Jan 7, 2019 · It is ok to call commit()-- either from the Processor or from a Punctuation -- that's why this API is offered. Aug 24, 2016 · The problem was that my ProcessorSuppliers were returning the same instance of the Processor for every call to get. x; Spring Kafka - Added Store cannot access from stream process A high-throughput, distributed, publish-subscribe messaging system - a0x8o/kafka Schedule a periodic operation for processors. Kafka Connect Kafka Streams Powered By Community Blog Kafka Summit Nov 20, 2024 · Processor API 基本操作. 11. punctuate(long). 1 概述. A processor may call this method during initialization or processing to schedule a periodic callback — called a punctuation — to Punctuator. Currently Kafka Streams provides two sets of APIs to define the processor topology, which will be described in the subsequent sections. No, they don’t run inside the Kafka brokers. With the Processor API, you can define arbitrary stream processors that process one received record at a time, and connect these processors with their associated state stores to compose the processor topology that represents a customized processing logic. Kafka Connect Kafka Streams Powered By Community Blog Kafka Summit May 24, 2024 · I figure out that the store was not properly initialized. api package, otherwise the metadata are not correct. Nov 13, 2018 · However with the DSL I have a StreamsBuilder/KStream. Jun 3, 2019 · You can get a topic name you need using ProcessorContext. Kafka Streams是一个客户端程序库，用于处理和分析存储在Kafka中的数据，并将得到的数据写回Kafka或发送到外部系统。Kafka Stream基于一个重要的流处理概念。如正确的区分事件时间和处理时间，窗口支持，以及简单而有效的应用程序状态管理。 Forward a record to all child processors. Oct 12, 2023 · When you are using Spring Kafka Streams you don't need to define and create a KafkaStreams bean. This will be done by Spring for you, however you do need to give it some sort of Topology to run, as you have noticed. “Kafka Streams applications” are normal Java applications that use the Kafka Streams library. 0 PunctuationType. Jan 18, 2024 · Kafka Streams의 Topology는 이 네트워크 토폴로지와 동일하다고 생각할 수 있다. source -> selectKey -> filter -> aggregate (on a window) -> sink Forward a record to all child processors. This section explores various common use cases for ProcessorSupplier, highlighting its flexibility and utility in building robust stream processing applications. I'm adding a state store here. Jan 8, 2024 · Connect with experts from the Java community, Microsoft, and partners to “Code the Future with AI” JDConf 2025, on April 9 - 10. Jul 1, 2021 · kafka Streams 1 概述 1. If a topic has four partitions and there are four instances of the same Kafka Streams processor running, then each instance maybe responsible for processing a single partition from the topic. processor. So, basically, a record can be forwarded to children processors using context. ProcessorContext with added generic parameters <K, V> code snippet below shows how the new API compares to processor. Jan 14, 2021 · If the application reaches the UncaughtExcpetionHandler, then the stream thread is already stopped and too late to recover. Kafka Stream？ Kafka Streams是一套处理分析Kafka中存储数据的客户端类库，处理完的数据或者写回Kafka，或者发送给外部系统。 Kafka Streams uses the concepts of stream partitions and stream tasks as logical units of its parallelism model. errors. A Apr 25, 2018 · Kafka Streams offers fault-tolerance and automatic recovery for local state stores. StateStoreSupplier; import org. fnra xay tbowm gdskp dsrs btte pwtywf fxd nqls sngemwo zsafvulu dnbho vtyn sitd alyu