TaskManagement Using Zookeeper Recipe

A typical use case in distributed system is " There are T tasks and P processes running but only T processes must be active always [ P > T ] and remaining P-T processes acting as stand by and be ready to take up a Task with one or more active processes fail".

Zookeeper provides an excellent service which can be used to co ordinate among P processes and using the mechanism of locking we can ensure that there is always T processes active. Without a central co-ordinating service generally there will be 2T processes[ i.e atleast one back up for each process]. With Zookeeper we can decide P based on the failure rate.

The assumption here are
1. At any time we have P > T. P can be chosen appropriately based on failure rate.
2. The tasks are stateless. That is any process P_i that takes up a task T_j does not know the state of the process P_k which previously processed T_j. This is not entirely true and there are ways to over come this draw back on a case by case basis.

This was developed for a different project S4 which is also open sourced http://s4.io/. The communication layer and task management layer is completely independent of S4 and can be used in any application.