cancel
Showing results for 
Search instead for 
Did you mean: 
Reply
BLawless
Frequent Visitor

On Error Block not triggering and catching error, resulting in flow failing

Hey guys, y'all were pretty helpful with a deeper concept I was trying to wrap my head around, so it's time for a softball (because I'm pretty sure the issue is located between the keyboard and the computer chair).

I've been trying to implement "On Block Error" blocks that will catch any errors thrown by the actions they are encapsulating and handle them so the main flow doesn't fail. Every attempt at this however has failed to catch any errors thrown by the actions the block encapsulates, this is both when I just have actions as well as when I have calls to sub flows that are contained within an "On block error" action. 

To help visualize my issue (see pictures below) I created a very basic "example" flow that creates an array of a certain length and, inside of an "On block error" action, it will attempt to assign a a value to an index that is out of bounds for the array (and should therefore throw an IndexOutOfBoundsException upon attempting that action).

I have not set individual error handling actions (namely because "Set varaible" does not have any "on error" properties), but this is applicable to actions that also have individual error handling properties. Every time the flow attempts the action it will cause the whole flow to fail with a runtime error of the index being invalid. The "On Block Error" is not set to throw an error in response to catching one, so the error causing the flow to fail (from my observations) is the one thrown by the action inside of the "On block error" block. It is worth noting that I in the example I am calling this sub-flow from the Main flow, which has the sub-flow call encapsulated in another "On block error" action, which means two different "On block error" actions have failed to catch and handle this error.

I have tried setting it to "Continue flow run" and either "go to the end of block", "run sub-flow", "go to beginning of block", etc. None of these actions take place, it simply behaves as if it didn't catch the error and the error made its way unhandled to the main flow runtime level and caused the flow to fail. 

I'm hoping this is just a simple configuration issue but if there are limitations to the "On block error" action that I am not aware of then I will happily expand on other scenarios where I am implementing this action (because none of my attempts with "On block error" have been successful thus far). 
Error thrown from the previous run at the bottom reports that the flow was stopped because of the action performedError thrown from the previous run at the bottom reports that the flow was stopped because of the action performed"On Error Block" configuration"On Error Block" configuration


2 ACCEPTED SOLUTIONS

Accepted Solutions
yoko2020
Responsive Resident
Responsive Resident

@BLawless 

I agree with your statement, applying individual exception in every action is ridiculous approach if we have complex flow.

 

But this is the reality, there are some action/error which did not get captured by On Block error. It still does not work as we expected same as like we apply Try Catch Exception in C#/Vb.Net.

View solution in original post

Rkv_
Resolver II
Resolver II

Hello Everyone, 

The Onblock error can only able to capture the failures happened with the actions which contain on error property and the errors listed with in the advanced tab of the on error.

 

For example the below action Get window contains On error.

 

Rkv__1-1630316620306.png    

Rkv__2-1630316661006.png

So the Onblock error able to capture if this action failed to get window.

The below action is the IF condition, which don't have on error, and this cannot be captured in Onblock error.

Rkv__3-1630316786825.png

 

 

 



View solution in original post

8 REPLIES 8
Henrik_M
Super User
Super User

Power Automate Desktop cannot handle IndexOutOfBounds exceptions 👎

 

If you are not 100% sure that the index will be valid during execution, you will have to do a manual check (using %List.Count%) instead of relying on the block error...

If the "On Block Error" doesn't catch errors like IndexOutOfBounds Exceptions then what errors are they capable of catching? Is there a reference list somewhere? 

 

I do agree with you that there are means to verify whether or not something should cause an error before performing the action (and make the actions performance conditional to that verification), but with complex flows there's a lot of edge cases that would be better off handled by a simple "On Block Error" segment. In my experience, individually checking all these cases for an error triggers would severely impact the readability and debug performance of the flow. 

yoko2020
Responsive Resident
Responsive Resident

@BLawless 

I agree with your statement, applying individual exception in every action is ridiculous approach if we have complex flow.

 

But this is the reality, there are some action/error which did not get captured by On Block error. It still does not work as we expected same as like we apply Try Catch Exception in C#/Vb.Net.


@yoko2020 wrote:

But this is the reality, there are some action/error which did not get captured by On Block error. It still does not work as we expected same as like we apply Try Catch Exception in C#/Vb.Net.




Marking this as the solution since it touches directly on the general issue, which is that the "On Block Error" doesn't capture every exception the same way a Try-Catch block does in other contexts.

From what I've gathered here it seems that the only errors that the "On Block Error" catches are those listed under the "advanced" segment of the actions "on error" actions. If this is true then actions such as assigning variables are capable of throwing errors that the "On Block Error" cannot handle. This is unverified but makes the most sense based on the discussion here and my observations. 

yoko2020
Responsive Resident
Responsive Resident

Here is just sample, and there are many more i can not remember.

This error did not catch by the On Block error.

 

That means if you have internal subflow function for handling global exception, it will not be executed.

(EX: if %GeneralException% = 1 then take a screenshot of desktop and send it via email )

 

Spoiler
2021-08-29_084245.png
Rkv_
Resolver II
Resolver II

Hello Everyone, 

The Onblock error can only able to capture the failures happened with the actions which contain on error property and the errors listed with in the advanced tab of the on error.

 

For example the below action Get window contains On error.

 

Rkv__1-1630316620306.png    

Rkv__2-1630316661006.png

So the Onblock error able to capture if this action failed to get window.

The below action is the IF condition, which don't have on error, and this cannot be captured in Onblock error.

Rkv__3-1630316786825.png

 

 

 



BLawless
Frequent Visitor


@Rkv_ wrote:

Hello Everyone, 

The Onblock error can only able to capture the failures happened with the actions which contain on error property and the errors listed with in the advanced tab of the on error.




Thank you @Rkv_  for confirming my theory posted in my last comment (here). Going to update the post to represent your comment as the solution as it points out the core issue. 

The previously marked solution by @yoko2020 is still input valuable as it touches on the core of how PAD under the hood isn't a programming/scripting language but features script-like operations to allow non-programmers to use the automation without having to learn a full programming language and has some limitations as a result (which we may be able to mitigate, see followup further down). 


@yoko2020 wrote:

But this is the reality, there are some action/error which did not get captured by On Block error. It still does not work as we expected same as like we apply Try Catch Exception in C#/Vb.Net.



Furthermore thank you for your example contribution (found here). 

 


As a followup:

I think there is a workaround but it may take some time to verify.

It might be possible (in cases where doing checks for validation on all edge cases is impossible with other actions) to perform the analog equivalent of the PAD action inside of a "Run JavaScript" action and use a try-catch block there (the one under "System", not "Run JavaScript on webpage unless you're using a browser to perform actions on a page). Knowing how variables work between the translation layer of a "Run JavaScript" action and the variable assignment in the flow, this will not work for every scenario, but I think a combination of this and using validation checks using other actions in PAD will cover most (if not all) of advanced edge cases. 

If JavaScript isn't your thing, "Run Python script", "Run VBScript", "Run PowerShell script", and any other "Run [Insert Programming Language here] Script" that Microsoft implements into PAD in the future (C#?) are good alternatives. 

I know for non-programmers this may not be ideal, but if you're running into scenarios where you need the full function of a try-catch block, chances are you're at the level to learn enough about one of these languages to do a try-catch block and scripting analog of whatever action you're wanting to perform in PAD. 

Anonymous
Not applicable

💩This is pain in butt. Try-Catch construction that cannot be trusted is a nightmare. It makes it really difficult to explain to customers why the robot terminated without sending any email warning as it should by the process design...  💩

Helpful resources

Announcements

Check Out the February 2024 Dynamics 365 Newsletter

Some of our most active Power Platform Community members are also active in our D365 Community. This month, we are excited to share the latest news from the D365 Community with you.   Our Dynamics365 Community has updated yet again! Since launching in June of 2023, the new Community has seen consistent updates and exciting new ways to feature and celebrate its members. In the latest edition of the Dynamics365 Community newsletter, you can see the new Leaderboard feature! This feature showcases which Community members have earned the most points over the previous month, enabling them to see how they are doing with their engagement--and their progress toward Super User status. Visit the leaderboard for yourself: https://aka.ms/d365clb     Read the whole newsletter featuring the new leaderboard as well as the D365 Monthly Community Member spotlight, FastTrack Tech Talks, upcoming events, and more. February 2024 Dynamics 365 Community Newsletter

Celebrating a New Season of Super Users with Charles Lamanna, CVP Microsoft Business Applications

February 8 was the kickoff to the 2024 Season One Super User program for Power Platform Communities, and we are thrilled to welcome back so many returning Super Users--as well as so many brand new Super Users who started their journey last fall. Our Community Super Users are the true heroes, answering questions, providing solutions, filtering spam, and so much more. The impact they make on the Communities each day is significant, and we wanted to do something special to welcome them at our first kickoff meeting of the year.   Charles Lamanna, Microsoft CVP of Business Applications, has stressed frequently how valuable our Community is to the growth and potential of Power Platform, and we are honored to share this message from him to our 2024 Season One Super Users--as well as anyone who might be interested in joining this elite group of Community members.     If you want to know more about Super Users, check out these posts for more information today:    Power Apps: What is A Super User? - Power Platform CommunityPower Automate: What is A Super User? - Power Platform Community Copilot Studio: What is A Super User? - Power Platform Community Power Pages: What is A Super User? - Power Platform Community

February 2024 User Group Update: Welcoming New Groups and Highlighting Upcoming Events

It's a new month and a brand-new year, which means another opportunity to celebrate our amazing User Groups!Each month, we highlight the new User Groups that have joined the community. It's been a busy season for new groups, because we are thrilled to welcome 15 New User Groups! Take a look at the list below, shared by the different community categories. If your group is listed here, give this post a kudo so we can celebrate with you!   We love our User Groups and the difference they make in the lives of our Community! Thank you to all the new User Groups, new User Group leaders--we look forward to hearing about your successes and the impact you will leave!   In addition to our monthly User Group spotlight, it's a great time to share some of the latest events happening in our User Group community! Take a look at the list below to find one that fits your schedule and need! There's a great combination of in-person and virtual events to choose from. Also, don't forget to review the many events happening near you or virtually! It's a great time of year to connect and engage with User Groups both locally and online. Please Welcome Our NEW User Groups   Power Platform: Heathcare Power Platform User Group Power Platform Connect Hub Power Platform Usergroup Denmark Mexico Norte- Power Platform User Group Pune Power User Group Sudbury Power Platform User GroupMicrosoft User Group GhanaMPPBLR - Microsoft Power Platform Bengaluru User Group Power Apps:   Myrtle Beach Power Platform User GroupAnanseTechWB PowerApps Copilot Studio: Pathfinders Power Platform Community Dynamics365: Cairo, Egypt MSD 365 Business Central/NAV/F&O User GruopMS Dynamics 365 Business Central LatamCincinnati OH D365 F&O User Group February User Group Events February 2024 Cleveland Power Platform User GroupPortallunsj - Februar 2024Indiana D365/AX February User Group MeetingQ1 2024 KC Power Platform and Dynamics 365 CRM Users Group 

January 2024 Community Newsletter

Welcome to our January Newsletter, where we highlight the latest news, product releases, upcoming events, and the amazing work of our outstanding Community members. If you're new to the Community, please make sure to follow the latest News & Announcements in each Community and check out the Community on LinkedIn as well! It's the best way to stay up-to-date in 2024 with all the news from across Microsoft Power Platform and beyond.      COMMUNITY HIGHLIGHTS Check out the most active community members of the last month! These hardworking members are posting regularly, answering questions, giving (and receiving!) kudos, and consistently providing top solutions in their communities. We are so thankful for each of you--keep up the great work! If you hope to see your name here next month, make it your New Year's Resolution to be more active in the community in 2024.   Power AppsPower AutomateCopilot StudioPower PagesWarrenBelzWarrenBelzPstork1saudali_25LaurensMPstork1stephenrobertLucas001AARON_ClbendincpaytonSurendran_RANBNived_NambiarMariamPaulachanNikhil2JmanriqueriosANBJupyter123rodger-stmmbr1606Agniusstevesmith27mandelaPhineastrice602AnnaMoyalanOOlashynBCLS776grantjenkinsExpiscornovusJcookSpongYeAARON_CManishSolankiapangelesPstork1ManishSolankiSanju1Fubar   LATEST NEWS Power Platform 2024 Release Wave Highlights This month saw the 2024 Release Wave 1 plans for Microsoft Power Platform and Microsoft Dynamics 365- a compilation of new capabilities planned for release between April and September 2024. Click here to read Corporate Vice President Maureen (Mo) Osborne's detailed breakdown of the upcoming capabilities, and click the image below to check out some of the Power Platform 2024 Release Wave 1 highlights.     "What's New" Power Platform Shorts Series This month we also launched our brand-new 'Power Shorts' series on YouTube - a selection of super sweet snapshots to keep you in the loop with all the latest trends from across the Power Platform and beyond. Click the image below to check out the entire playlist so far, and don't forget to subscribe to our YouTube channel for all the latest updates.   Super User In Training (S.U.I.T) It was great to see the Power Platform Community officially kick off Season One of their Super User in Training (SUIT) program this month! Their first meeting saw an amazing turnout of over 300 enthusiastic participants who started their dynamic journey toward becoming Super Users. Huge thanks to Manas Maheshwari, Eric Archer, Heather Hernandez, and Duane Montague for a fantastic kick-off. The first meeting also saw seasoned Super User, Drew Poggemann, share invaluable insights on navigating the #MicrosoftCommunity with finesse. Many thanks to Drew for setting the stage and emphasizing the importance of active engagement and the art of providing thoughtful community solutions. If you want to learn more about the features and benefits of gaining Super User status, click the image below to find out more, and watch this space for more info about Season Two and how you can SUIT UP in the community!     UPCOMING EVENTS Microsoft 365 Community Day - Miami - February 1-2, 2024 It's not long now until the Microsoft 365 Community Day Miami, which will be taking place at the Wolfson Campus at Miami Dade College on 1-2 Feb. 2024. This free event is all about unlocking the full potential of Power Platform, Microsoft 365, and AI, so whether you’re a tech enthusiast, a business owner, or just curious about the latest Microsoft advancements, #M365Miami is for you.   The event is completely free and there will sessions in both English and Spanish to celebrate the vibrant and diverse make-up of our amazing community. Click the image below to join this amazing Community Day in Miami and become a part of our incredible network of learners and innovators!     Microsoft Fabric - Las Vegas - March 26-28, 2024 Exciting times ahead for the inaugural #MicrosoftFabric Community Conference on March 26-28 at the MGM Grand in Las Vegas. And if you book now, you can save $100 off registration! The Microsoft Fabric Conference will cover all the latest in analytics, AI, databases, and governance across 150+ sessions.   There will be a special Community Lounge onsite, interactive learning labs, plus you'll be able to 'Ask the Experts' all your questions to get help from data, analytics, and AI specialists, including community members and the Fabric Customer Advisory Team. Just add the code MSCUST when registering for a $100 discount today. Click the image below to find out more about the ultimate learning event for Microsoft Fabric!     Microsoft 365 Conference - Orlando - April 30 - May 2, 2024 Have you added The Microsoft 365 Conference to your community calendar yet? It happens this April 30th - May 2nd in Orlando, Florida. The 2024 Microsoft 365 Conference is one of the world’s largest gatherings of Microsoft engineers and community, with a strong focus on Power Platform, SharePoint, Azure, and the transition to an AI-powered modern workplace.   Click the image link below to find out more and be prepared to be enlightened, educated, and inspired at #M365Conf24!   LATEST COMMUNITY BLOG ARTICLES Power Apps Community Blog Power Automate Community Blog Copilot Studio Community Blog Power Pages Community Blog Check out 'Using the Community' for more helpful tips and information: Power Apps, Power Automate, Copilot Studio, Power Pages  

Super Users 2024 Season One is Here!

   We are excited to announce the first season of our 2024 Super Users is here! Our kickoff to the new year welcomes many returning Super Users and several new faces, and it's always exciting to see the impact these incredible individuals will have on the Community in 2024! We are so grateful for the daily difference they make in the Community already and know they will keep staying engaged and excited for all that will happen this year.   How to Spot a Super User in the Community:Have you ever written a post or asked for help in the Community and had it answered by a user with the Super User icon next to their name? It means you have found the actual, real-life superheroes of the Power Platform Community! Super Users are our heroes because of the way they consistently make a difference in the Community. Our amazing Super Users help keep the Community a safe place by flagging spam and letting the Community Managers know about issues. They also make the Community a great place to find answers, because they are often the first to offer solutions and get clarity on questions. Finally, Super Users share valuable insights on ways to keep the Community growing, engaging, and looking ahead!We are honored to reveal the new badges for this season of Super Users! Congratulations to all the new and returning Super Users!     To better answer the question "What is a Super User?" please check out this article: Power Apps: What is A Super User? - Power Platform CommunityPower Automate: What is A Super User? - Power Platform Community Copilot Studio: What is A Super User? - Power Platform Community Power Pages: What is A Super User? - Power Platform Community

Did You Attend the Microsoft Power Platform Conference in 2022 or 2023? Claim Your Badge Today!

If you were one of the thousands of people who joined us at the first #MPPC Microsoft Power Platform Conference in 2022 in Orlando--or attended the second-annual conference in Las Vegas in 2023--we are excited to honor you with a special community badge! Show your support for #MPPC Microsoft Power Platform Conference this year by claiming your badge!           Just follow this link to claim your badge for attending #MPPC in 2022 and/or 2023: MPPCBadgeRequest    Want to earn your badge for 2024? Just keep watching our News & Announcements for the latest updates on #MPPC24.

Top Solution Authors
Top Kudoed Authors
Users online (2,669)