There was a build failure where one of the heartbeat threads timed out trying to connect to the mongod, causing the test to fail. Heartbeat threads are used to keep idle cursors alive.

This happened on a UBSAN+Debug variant. I think the 5-second limit to establish a connection may be the cause here.

There are two things we can try doing here:

• Don't run backup/restore tests on UBSAN+Debug due to the variants slowness
• The heartbeat thread should retry connecting to the mongod