On the page you linked:

>However, if a database has many concurrent overlapping readers and there is always at least one active reader, then no checkpoints will be able to complete and hence the WAL file will grow without bound.

>This scenario can be avoided by ensuring that there are "reader gaps": times when no processes are reading from the database and that checkpoints are attempted during those times.

Dunno, maybe Rails has a built-in workaround for this.

My workaround was to run a separate thread that monitored the WAL size on disk every second. If it went above the target size of 8 MB, my framework would enter "slow down" mode, where all reads and writes were artificially delayed by calling "sleep()", starting at 16 ms and gradually increasing the sleep time based on a few heuristics.

This allowed the application to have short gaps with no reads or writes, so the checkpointer could actually proceed.