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![]() When process.roles is not configured, it is assumed that the cluster will run in Zookeeper mode. The controllers can either be in active or standby mode which will eventually take over if the currently active controller server fails or is taken down.īroker: The Kafka server shall serve as a brokerĬontroller: The Kafka server shall serve as a controller of the internal Raft quorumīroker,controller: The Kafka server shall serve as both a controller of the quorum and a broker When KRaft mode is enabled, only a few selected servers can serve as controllers and these will compose the internal quorum. The nodes of the cluster can now serve as brokers, controllers, or both (called combined nodes). This internal topic is managed by the internal quorum and replicated across the cluster. This topic has a single partition and the leader will be on the active controller. When Kafka Raft Metadata mode is enabled, Kafka will store its metadata and configurations into an internal topic called _cluster_metadata. In the latest release, ZooKeeper can be replaced by an internal Raft quorum of controllers. To overcome the challenges of Zookeeper in Kafka, a KIP (Kafka Improvement Plan) was submitted for Zookeeper-less Kafka ( KIP-500) and version 2.8.0 introduced early access to Zookeeper-less Kafka, with KRaft becoming production-ready in version 3.3.0. Also, it has to send all metadata to all the brokers. The Zookeeper-based Kafka controller loads all the metadata synchronously on startup and during this time the cluster is unavailable. Given that the amount of metadata gets bigger over time, this means that the loading of such metadata becomes more inefficient over time and thus limiting the number of partitions the cluster can store. Every time the cluster is starting up, the Kafka controller must load the state of the cluster from Zookeeper.įewer Partitions in the Cluster- The same happens when a new controller is elected. Limits Kafka Scalability- With Zookeeper, Kafka scalability is limited. Therefore, if you want to deploy a Kafka cluster then you would also have to manage, deploy, and monitor Zookeeper as well.Įrror Prone- These two distributed systems require different configurations and the level of complexity increases, thus it is much easier for system administrators to make mistakes.ĭuplication of work- Having two systems also leads to duplication of work- for example, in order to enable security features you would have to apply the relevant configuration to both services.Īdditional Processes- Having an external metadata store is inefficient regarding resources as you need to run additional processes. Two different systems - Zookeeper is an external system to Kafka which means that it comes with its own configuration syntax, management tools, etc. Zookeeper provides multiple features for distributed systems: This kind of meta-information is usually measured in kilobytes, if not bytes. Zookeeper was designed to store coordination data: status information, configuration, location information, etc. The main difference between Zookeeper and standard file systems is that every zNode can have data associated with it. Its strict ordering allows sophisticated synchronization primitives to be implemented at the client. The reliability aspects prevent it from becoming the single point of failure in big systems. The performance aspects of Zookeeper allow it to be used in large distributed systems. Zookeeper allows distributed processes to coordinate with each other through zNodes. Zookeeper is a service for maintaining configurations, naming, and distributed synchronization. Finally, what are the limitations of Zookeeper, and how does KRaft mode mitigate those limitations? Zookeeper in Kafka What is Zookeeper Next, we'll see what its role is in Kafka. In this article, we’ll first discuss what Zookeeper is. The new feature simplifies cluster administration and infrastructure management and makes the Kafka cluster more scalable. The release of Apache Kafka 3.3.0 saw KIP-500 become production-ready, meaning Kafka now relies on an internal Raft quorum that uses a Kafka Topic to store metadata, and some Kafka servers act as Controllers. From the release of Apache Kafka 2.8.0, users have had early access to KIP-500, which removes the Zookeeper dependency from Kafka.
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