3 posts tagged with "distributed-computing"

Session and request order handling:​

Sessions is very important and quite critical for the operation of ZooKeeper. All operations a client submits to ZooKeeper are associated to a session. When a session ends for any reason, the ephemeral nodes created during that session disappear.

The client initially connects to any server in the ensemble, and only to a single server. It uses a TCP connection to communicate with the server, but the session may be moved to a different server if the client has not heard from its current server for some time. Moving a session to a different server is handled transparently by the ZooKeeper client library.

Zookeper data Model:​

ZooKeeper has a hierarchal name space(as shown below), much like a distributed file system. The only difference is that each node in the namespace can have data associated with it as well as children. It is like having a file system that allows a file to also be a directory.

Zookeper is an open-source, centralised co-ordination service which is used to co-ordinate the services and manage the configurations of applications accross a large number of hosts over a distributed environment.

Co-ordinating between the services in a distributed application is a complex process. ZooKeeper was designed to be a robust service that enables application developers to focus mainly on their application logic rather than coordination. It exposes a simple API, similar to filesystem API, that allows developers to implement common co‐ordination tasks, such as electing a master server,managing group membership, and managing metadata.

Zookeper is open-sorced to Apache by Yahoo. Apache Zookeper have became standard for organising the services in Hadoop, kafka and other distributed frameworks.