Is concurrenct thread safe in PowerAutomate?

[Kran]

If I set a variable with a value within a loop and then turn on concurrency - will it be thread safe?

Or can one thread change the value of the variable which will affect another thread?

Is there a recommendation to avoid concurrency when we set variables within the loop? Is there any workaround?

[tom_riha]

Hello @Kran ,

if you use variable in a parallel loop, all the parallel runs will access it at the same time. It's ok if you only read the variable, but if you also update it, it'll be a mess.

If it's possible, you can use a 'Compose' action instead of a variable, each parallel branch will have its own 'Compose' action with its own input/output.

[Kran]

@tom_rihaThanks for your reply! That was very good information!

But how can I set a variable inside a compose action?

In my situation, as of now, I have a SWITCH case, where I for each of the cases, set a variable which is then used to set a column on a new record.

Do you see anyway to solve this with a compose action? Thanks!

[v-xiaochen-msft]

Hi @Kran ,

You could use 3 compose actions or create 3 variables to solve it.

Best Regards,

Wearsky

[Kran]

thanks for your reply!
So that If statement checks whether the first condition is empty? And if is, then it checks next one?

[v-xiaochen-msft]

Hi @Kran ,

Please use  switch conditions in your If expression .

Flow needs to know which compose action to use .

Best Regards,

Wearsky

[tom_riha]

Hello @Kran ,

I was thinking about the problem and I wrote a blog post with my solution: https://tomriha.com/using-variable-in-a-parallel-loop-in-power-automate-flow/.

Use an array variable, instead of the 'Set variable' use 'Append to array variable' while including some unique identifier of each item + the corresponding value. Filter only the corresponding value from the array and use it in the 'Add row...' action.