I have a log of the form
"Associated integration for customer AAA is Integration{id=1865, clientID}, carrying out deactivate call while processing message success"
I wanted to extract the AAA which is the customer name from this log
| rex field=_raw "Associated integration for customer (?<customer_name>[\w]+)"
The statement in the quotes is a regex that is used to match and capture the name as the field customer_name
If the customer name is a sequence of normal A-Z upper/lower case characters the \w is sufficient, however, if there are other characters in the name, then put those character classes inside the [] and add in the extra constraining text after the customer name,