WSO2 good practice with many service calls in a sequence

Question

I'm working on a scheduled sequence that need to do the following tasks:

call GetNew data service getting possible new xml data
if xml exists
    with the xml data, get the ID and save it into a property
    call UpdateStatus data service with the parameters ID and PROCESSING
    call the ProcessOrder service passing the xml data
    if the return is success
        call the external SetStatus service with SUCCESS
    otherwise
        call the external SetStatus service with ERROR 
    call UpdateStatus data service again with the parameters ID and PROCESSING
otherwise
    do nothing

For do that, I've build the following sequence:

payload -- to build a GetNew request
callout -- to call the GetNew data service
property -- to save the ID from the possible new message
filter -- verify if the ID property exists
    then
        clone
            payload -- to build a UpdateStatus PROCESSING request
            callout -- call the UpdateStatus
        xslt -- transform the XML from GetNew to the ProcessOrder
        in
            send -- to the ProcessOrder endpoint
        out
            property -- save the status of the ProcessOrder response
            payload -- to build the SetStatus request
            callout -- call the external SetStatus service with the status
        payload -- to build a UpdateStatus PROCESSED request
        callout -- call the UpdateStatus
    else
        drop

I would like to know if this is a good practice, or if I should split it into many sequences, or replace the callouts by send, and how is the best way to deal with SoapFaults using this approach.

Thanks in advance.

Answer 1

Breaking into many sequences in a design decision. Generally sequence is more like a class. If a particular sequence does a specific task, it will be cohesive and highly reusable in other scenarios as well. So better break based on the logical task performed through the sequence.

Using callout or send mediator depends on the usecase you are trying to achieve. Precisely send mediator differs from callout by making the call asynchronous. So callout mediator makes a blocking call, but this will be useful if you need the response from the service to proceed with the sequence. You can get more details about these mediators on the following link. http://docs.wso2.org/display/ESB480/Mediators

For proxy services and sequences you can define fault sequences to handle fault scenarios. For more on error handling you can follow http://docs.wso2.org/display/ESB480/Error+Handling.