How to store request response data concurrently - jmeter-5.0

Question

i'm setting a test plan running this thread groups sequentially:
Execute request A using 10 threads, 500 loops.
Execute request B using 10 thread, 500 loops, and the output from step 1.
My problem is this:
On each request A, i receive an ID that i need to pass to request B.
What is the best way to store all the IDs and then use them on step 2?
At this time, i am "JSonExtracting" each ID from response and store on a CSV file to pass to step 2.
The problem is the concurrence of the treads. Some times i got empty spots on the file or concatenated strings which will produce an error on step 2.
I was not able to store this to an array variable to use on step 2.
To write the IDs to a file, i am using this code on a BeanShell Listener inside my threadGroup. I strongly believe this is not the most correct way to do it.
f = new FileOutputStream("${DocumentIdsFile}", true);
p = new PrintStream(f);
p.println("${DocumentId}");
p.close();
f.close();
log.info("Id: ${Id}");
How can i solve this concurrence problem?

Answer 1

If you receive an ID at the request A, just use it in request B, passing it throug variable:
Parse ID value in request A response using one of the Post-Processors to store it in variable, for example "ID".
Use it's value in your request B as a parametr:
GET https://myserver.com/myapp/getSomethig/${ID}