Error Handling in Mulesoft

[15th Aug 2020]
[Mule 4 Error Handling]
[Faridabad - India]

All contents © MuleSoft Inc.
Sensitivity: General
Agenda
2
➢ Community Introduction
➢ Introduction to Error Handling
➢3 Rules to Understand Error Handling
➢Demo
➢Try-Until Successful scopes
➢Error Handling - Priority
➢Q & A session
➢Quiz
➢Networking time

Organizers
3
Welcome everyone! Thanks for joining us!

Surprises!
4
• Participate in an online
Quiz to win the
instructor-led training
classes and certification
exam vouchers. (3
Winners!)
• Be geared up for the
quiz sessions at the end


Error Handling
6
• An exception occurs when an unexpected
event happens while processing.
• Exception handling is the process of
responding to exceptions when a computer
program runs.
• In Mule we can handle the message exception
at different levels.

Error Handling
7
• At Project level using Default error handler
• At Project level using Custom Global error handler
• At Flow level in exception handling using :
On Error Continue
On Error Propagate
Raise Error
• With in Flow or at processor level using try scope

Error Handling
8
• Whenever there is an error occurred in a Flow, an error Object is created
• It contains many properties . Eg : error.description , error.errorType etc.
• Mule identifies based on errorType and then route to respective blocks that are
placed in Error Handler.
• errorType is combination of Namespace and Identifier :
Eg : HTTP:UNAUTHORIZED
• namespace = HTTP
Identifier = UNAUTHORIZED

Error Handling
9
• Sub-Flow doesn’t have Error Handling scope .
• So its just Flow and a Private flow where you can place On-Error-
Propagate and On-Error-Continue inside “Error Handling” block.
• Either it is Propagate or Continue, Mule Executes all the components
within that block.
Remember : The error will route to error-handling only if it identifies
that the errorType of that error is handled

Error Handling
10
• Mule 4 has one excellent feature of Identifying the types of
errors that can occur within that flow by looking at what
kind of connectors are placed in that particular flow.

3 Rules to Understand Error Handling
11

Rule 1 : Error handling
12
• See if anything is present in Error-Handling .
• Even if there are on-error-propagate and on-error-continue blocks, see that if that
particular errorType is handled.
• If NOT, then Mule will use default Error Handling .
• And if your flow is not called by any other flow , then it will display default value that is
set in Error-Response of HTTP Listener and gives status code as 500 bad default if
nothing is set manually.
• If your flow is called by any other flow, then it will RAISE as an error to the calling flow.

13
• If some Error Handling is present in that particular flow and errorType is
handled (YES condition for RULE1) .
• Check whether it is On-Error-continue or On-Error-Propagate .
• In both the cases, Mule will execute all components within that Error block.
• Next follow Rule 3 which is very important !

14
• If the error is handled using On-Error Propagate , it will raise an error
back to the calling flow.
• If the error is handled using On-Error Continue , it will not raise an error
back to the calling flow but continue to next processor of “flow-ref” of
calling flow and continues further process as it is.
- But it will not continue to other processors in the flow where error is
handled (in On-Error Continue Case).

Rule 3 : Error handling ( Cont… )
15
• Suppose you have only single flow. Then On-error-propagate and On-error-
Continue behaves same way, instead error-continues gives 200 status and
error-propagate gives 500 status.
• Because as said , even if its error-continue, it will not go to next processor
within the same flow where error is Handled.
• Remember : This point is very important. On-error-Continue will continue only
to next processor of calling flow but not in the same flow

Error Handling - example 1
16
Rule 1
Rule 1 Output :
Default error message with 500
status

17
Rule 1
Output :
”Error Handled in Main flow”
with 200 status
Rule 2
Rule 3

18
Rule 1
Output :
”Error Handled in Main flow”
with 200 status
Rule 2
Rule 3
Rule 1
Rule 2
Rule 3

Error handling - Let’s get our Hands Dirty
19
Hands-on

Error Handling - Raise Error
20
• This core component generates a Mule error, as if a failure had occurred, which allows
you to customize its description and type.
• Use this component to only raise:
✓ Core runtime errors, such as MULE:SECURITY, MULE:CONNECTIVITY, etc.
✓ Custom error types. Eg : ORDER:INVALID
You cannot use a connector’s existing namespace.

Error Handling - Try , Until Successful
21
• Try and Until Successful scopes are handled at connector level.
• You can wrap one or more connectors within Try or Until Successful

Error Handling - Try , Until Successful
22
• Until Successful retries for all kind of errors. So make Sure when you use it for
HTTP Request component.
• The errorType for Until Successful is MULE:RETRY_EXHAUSTED
• When Error Continue is used within Try block , then it moves to Next processor.
When error propagate is used, it follows Rules of General Error Handling.
• For MUnits , its very important to have Try-Error continue combination for error

Error Handling - Priority
23
• The Error handling has its defined Precedence.
• The error that is handled at connector level takes 1st precedence , followed by
flow level and then global level and finally Default level
• Priorities of Error Handling :
✦ 1st priority - Connector Level
✦ 2nd priority - Flow level
Hands-on

Take a stand !
27
• Nominate yourself for the
next meetup speaker and
suggest a topic as well.
• Either for our virtual meetup
speaker, or in-person
meetup speaker.
• Surprise swag for upcoming
Speakers.
• Fill this form -
https://bit.ly/speakar

What’s next
28
• Share:
– Tweet/share in LinkedIn , facebook, Instagram with your pictures with the hashtag
#FaridabadMuleMeetup #MuleSoftMeetup
– Also use #BringMuleSoftConnectToFaridabad to reach our wish to MuleSoft 
– Invite your network to join: https://meetups.mulesoft.com/Faridabad/
• Feedback:
– Contact MuleSoft at meetup@mulesoft.com for ways to improve the program
– Your Feedback is Food for us. https://bit.ly/f-mf
• Our next meetup:
– Date: 29th August 2020, 5:00 PM IST
– Location: Virtual
– Topic: Ways to Externalize the Mule Application Logs

THANK YOU 
#Everyone
for becoming a part of such a great
#community.

Error Handling in Mulesoft

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