What is Apache Zookeeper? | Expert’s Top Picks | Free Guide Tutorial

What is Apache Zookeeper? | Expert’s Top Picks | Free Guide Tutorial

Last updated on 14th Dec 2021, Blog, General

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First, let’s have a look at concisely what the Zookeeper is. ZooKeeper could be a coordinative and managing service to an oversized set of hosts in a very distributed surroundings. ZooKeeper will this task with its easy design and API. to grasp the role of the Apache Zookeeper properly, it’s higher to own some plan on distributed applications.

    • Introduction to Apache Zookeeper
    • How Zookeeper achieves coordination?
    • Zookeeper information Model
    • Zookeeper APIs
    • Zookeeper Workflow
    • Benefits of ZooKeeper
    • Conclusion

    Introduction to Apache Zookeeper:

    In terribly easy words, it’s a central information store of key-value mistreatment that distributed systems will coordinate. Since it must be able to handle the load, Zookeeper itself runs on several machines.

    Zookeeper provides straightforward|a straightforward} set of primitives and it’s terribly easy to program to.

    It is used for:

  • Synchronization.
  • Locking.
  • Maintaining configuration.
  • Failover management.

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      How Zookeeper achieves coordination?

      Say, there’s inbox from that we want to index emails. categorization could be a significant method and would possibly take plenty of your time. So, you’ve got multiple machines that area unit categorization the emails. each email has Associate in Nursing id. you’ll be able to not delete any email. you’ll be able to solely scan Associate in Nursing email and mark it scan or uninformed. currently however would you handle the coordination between multiple skilled worker processes so each email is indexed? If indexers were running as multiple threads of one method, it absolutely was easier by the manner of mistreatment synchronization constructs of programing language.

      Zookeeper information Model:

    • The manner we tend to store information in any store is termed a knowledge model. within the case of the zookeeper, it uses a knowledge model sort of a directory tree.
    • Consider the information model as if it’s a extremely offered classification system with few variations.
    • We store information in entity known as znode. the information that we tend to store ought to be in JSON format that Java script object notation.
    • The znode will solely be updated. It doesn’t support append operations.
    • The scan or write is Associate in Nursing atomic operation that means either it’ll be full or would throw a slip if unsuccessful. there’s no intermediate state like half-written.
    • znode will have youngsters. So, znodes within znodes create a tree-like hierarchy. The commanding znode is “/”.

      Application of Zookeeper:

    • Let us say several servers will reply to your request and there area unit many purchasers which could need the service. From time to time a number of the servers can keep taking place. however will all of the shoppers will keep track of the offered servers?
    • It is terribly simple mistreatment ZooKeeper as a central agency. every server can produce their ephermal znode below a selected znode say “/servers”. The shoppers would merely question zookeeper for the foremost recent list of servers.
    • Let’s take a case of 2 servers and a consumer. the 2 servers duck and cow created their ephermal nodes below “/servers” znode. The consumer would merely discover the alive servers cow and duck mistreatment command ls /servers.
    • Say, a server known as “duck” is down, the ephermal node can disappear from /servers znode, and therefore next time the consumer comes and queries it might solely get “cow”.
    • So, the coordinations are created heavily simplified and created economical thanks to ZooKeeper.
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      Zookeeper APIs:

    • You can use the ZooKeeper from at intervals your application via Apis – application programming interface.
    • Though ZooKeeper provides the core Apis in Java and C, there area unit contributed libraries in Perl, Python, REST.
    • For each operate of Apis, synchronous and asynchronous variants area unit offered.
    • While mistreatment synchronous Apis the caller or consumer can wait until ZooKeeper finishes Associate in Nursing operation. however if you’re using asynchronous API, the consumer provides a handle to the operate that might be known as once zooKeeper finishes the operation.

      Zookeeper Workflow:

      Once a ZooKeeper ensemble starts, it’ll watch for the shoppers to attach. shoppers can hook up with one among the nodes within the ZooKeeper ensemble. it’s going to be a frontrunner or a lover node. Once a consumer is connected, the node assigns a session ID to the actual consumer Associate in Nursingd sends an acknowledgment to the consumer. If the consumer doesn’t get Associate in Nursing acknowledgment, it tries to attach another node within the ZooKeeper ensemble. Once connected to a node, it will perform functions like reading, writing, or storing the information as per the necessity. The consumer can PING to the node at an everyday interval to create positive that the affiliation isn’t lost.

      Use cases

      The common services provided by ZooKeeper area unit as follows:

      Naming service − characteristic the nodes in a very cluster by name.

      Configuration management − Latest and up-to-date configuration data of the system for a connexion node.

      Cluster management − connexion / going away of a node in a very cluster and node standing in time period.

      Leader election − Electing a node as a frontrunner for coordination functions.

      Locking and synchronization service − lockup the information whereas modifying it. This is often utilized in automatic fail recovery whereas connecting different distributed applications.

      Highly reliable information register register accessibility of knowledge even once one or a couple of nodes area unit down.

      Benefits of ZooKeeper:

      Here is that the list of varied benefits of mistreatment Apache ZooKeeper:


      The operating of the Zookeeper is extremely synchronous , which suggests there’s a mutual exclusion also as co-operation between server processes. Basically, this synchronization helps in Apache HBase for the aim of configuration management.

      Ordered Messages

      Zookeeper track with variety, by denoting its order with the stamping of every update, through all the messages area unit ordered here.


      According to specific rules, Zookeeper encodes the information. to boot, it ensures that our application is running systematically or not. Though, in MapReduce, we tend to use this technique (Serialization) to coordinate queues to execute running threads.


      In the cases wherever ‘Reads’ area unit additional common, it runs with the quantitative relation of 10:1, that is nice speed.


      Furthermore, it’s potential to accentuate the performance of Zookeeper by deploying additional machines.

      How is that the Order Beneficial?

      As we know, Messages in Zookeeper is in good order. So, so as to implement higher-level abstractions that order is needed. That’s however the order United Stateseful|is helpful} for us.

      ZooKeeper is quick

      In the cases of “read-dominant” workloads, Apache Zookeeper works in no time.


      Also, we will say that Zookeeper is incredibly reliable. it’s as a result of as shortly because it applies the update till a consumer overwrites the update, which will persist from that point forward.


      There area unit solely 2 cases potential, either information transfer succeeds or rather fail fully. although there’s no case of the partial group action.


      In easy words, up-to-date, which means in some definite time quantity, the system’s client’s read is up-to-date or on time.

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      Apache ZooKeeper is employed for maintaining centralized configuration data, naming, providing distributed synchronization, and providing cluster services in a very easy interface so we do not ought to write it from scratch. Apache writer additionally uses ZooKeeper to manage configuration.

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