Mule - Processing Strategies

Hello Everyone,

This post will have a glance on what is Processing Strategy ? How we Choose it or how Mule Application selects by default etc.

This concept will help us to develop applications in a reliable way .

Processing Strategy determines how Mule implements Message processing for a given flow(s).

It determines by:

Ø Should message be processed synchronously or asynchronously? (Explained earlier)

Ø Should message be Non-Blocking strategy?

Ø If asynchronously , what are properties of pool of threads used to process messages.

Ø If asynchronously , how messages wait for their turn to be processed in 2^nd thread.

All Mule Flows have a Default or implicit Startegy which mule applies automatically.

Implicit Processing Strategy :

Even though we do not define Processing Strategy for flow created, it will be automatically applied by Mule. It can be :

a)    Synchronous flow Processing Strategy

b)    Queued Asynchronous flow Processing Strategy.

How does it selects???

It can be selected based on 2 criteria’s :

1)    Flow’s Exchange pattern :

There are two types of exchange patterns and based on it , the strategy is defined.

a) Request-response exchange pattern: It is used when sender, I.e, inbound endpoint expects response or some result to return to caller.

b) One-way Response exchange pattern: It is used when no-response is expected or when result is sent to some other flow.

If its request response processing strategy, then its Synchronous Processing Strategy.

2)    Whether or not flow is transactional :

If flow is transactional, then it is Synchronous Processing Strategy

Exchange Pattern	Transactional	Processing Strategy
Request-Response	Yes	Synchronous
Request-Response	No	Synchronous
One-way	Yes	Synchronous(because Transaction is Yes)
One-way	No	Queued Asynchronous

Note: Request-response ----- Blindly Synchronous

Transaction if Yes-----Blindly Synchronous

Some Options:

a)    Change to Synchronous : If mule selects Queued Asynchronous Processing Strategy , we can specify a Synchronous flow to achieve reliability.

b)    Fine Tune: We can accept Mule’s choice of Queued Asynchronous Processing Strategy , but fine-tune it . Remember, we cannot fine tune Synchronous Flow.

c)     Wrap a Flow: Inside async Scope, we can wrap one or more message processors to achieve Asynchronous Processing Strategy.

d)    Sub-flow: It’s a Synchronous Processing Strategy

e)    Non-Blocking Strategy: Available in 3.7+ version . To avoid having threads blocked while waiting for Http-responses, which also requires less tuning. (Note: Not all components are supported. Non supported components fall back to Synchronous Processing Strategy).

f)      Custom: We can create custom Processing Strategy by specifying in xml as :

<flow name=”xxx” processing strategy =” Processing Strategy name” >

Strategy	Description
Non-blocking	Applies using Http listener
Thread-per processor	Here every processor runs sequentially in different thread
Asynchronous	Not applicable in most cases
Queued -thread	Not applicable in most Cases