What does "Connection pool shut down" error mean?


Using webmethods.io, we have a REST connector that tries to pull data from a third-party service. The amount of data is big, and the service is rather slow to build it, so we take it paginated, and with the Response Timeout increased to 3 minutes in account’s settings. Problem is, after few pages received, the connector returns the error “Connection pool shut down”, and after that, any attempt to use that account in the connector, even for other, more short queries, ends with the same error. Creating another account with same settings revives the connector (and apparently requests to the third-party service start to come from another SAG cloud server IP), but only for few pages, then the same error appears.

Now, I realize that this particular connection is probably badly formed and exhausts some sort of resource that is limited to us by our service agreement… but what exactly that resource is? The amount of requests? Absolutely impossible, it dies after less than ten pages of a single query. The data size? The time spent on requests? Also unlikely, with other services we’ve been pulling much larger amounts of data on a daily basis, and there was no problem like that. Then what? The error message does not explain much.

Filtering the amount of data we’ve already tried and exhausted that option, so no need pointing that.

Thank you.

Update: the problem still persists.

The tenant is updated to

The vendor updated the system on their side, so individual pages come in a reasonable ~20 seconds time, yet after a couple of pages the error returns.

What kind of limitation could cause this error?