Do you know of a reliable way to induce a "Transport endpoint is not connected" trouble state in S3FS?
Yes, I know that S3FS is dodgy and that S3 is not meant for mounting as a normal file system. I realize there are other, better solutions than S3FS. I have read the other threads on SO and I'm not interested in re-hashing recommended alternatives at the moment. Some day, I may consider other alternatives, but I have a deadline and I want to stick to the topic.
I plan to try out things like autofs and cron-triggered remounting scripts and I want to be fairly sure that I'm testing potential solutions against as faithful a reproduction case as I can muster.
"Transport endpoint is not connected" means that the s3fs process exited without unmounting cleanly. Usually this is due to s3fs crashing, e.g., segmentation fault, memory corruption, etc. It should not occur under normal operation but you can simulate it by sending a signal to s3fs: kill -s SEGV $(pidof s3fs).
Newer versions of s3fs (1.89 as of this writing) address many of the previously-reported crashes. If you encounter one with the latest version, please re-run the s3fs with gdb attached and report the backtrace to the s3fs GitHub issue tracker so we can fix the root cause.