A brief explanation of Idempotent Filter and how messages are stored to prevent duplication in Mule and a basic example

1. Idempotent Filter

2. Overview
● It is an important message filter in Mule platform which ensures that only unique
messages are received by the service by checking the unique ID of the
incomming message
● It is used to avoid any duplicate messages in our flow
● To maintain which message have already arrived it uses Object Store
● An object store is a facility provided by Mule for storing objects thus persisting
data for eventual retrival
● Mule provides two types of object store:
● In-memory store: stores objects in local Mule runtime memory. Objects
are lost on shutdown of Mule runtime
● Persistent-store: Mule persists data when an object store is explicitly
configured to be persistent. In a standalone Mule runtime, Mule creates a
default persistent store in the file system

3. Various ways to configure Idempotent Filter
● Simple-text-file-store
● In-memory-store
● Managed-store
● Custome-object-store

4. Idempotent filter with simple-text-file-store
● Here we will configure our Idempotent filter with a basic simple-text-file-store
● Here text file will be generated in our Mule application where it will store the message ID to
avoid duplication
● Here we will also use Exception strategy to catch exception when a duplicate message is
inserted
● For that purpose we will make property throwOnUnaccepted=”true”

5. Flow Example

6. XML of the flow

7. Package Explore View
● As it can be seen here
idempotentStore folder is created in
our Mule Application to store text file
which holds the message ID to
prevent duplications