Description of problem:

When a LokiStack is configured as "1x.demo", the generated Loki configuration contains a "replay_memory_ceiling" value of zero. This value is respected by the ingester and leads to it immediately flushing each chunk during WAL-replay, which slows down ingester startup times considerably.

Version-Release number of selected component (if applicable):

5.9.2

Steps to Reproduce:

1. Create a LokiStack configured with "size: 1x.demo"
2. Look into the generated ConfigMap for the "replay_memory_ceiling" value

Actual results:

"replay_memory_ceiling" value is zero.

Expected results:

Use a more sensible value for the replay_memory_ceiling, while keeping the usage low for demo installations.

Additional info:

When this behavior of the ingester occurs it looks as if the ingester is "endlessly looping" on flushing the logs, because almost each line is flushed to object storage on its own.

It is no endless loop though, it is just very slow. Flushing after a restart can take a few minutes even on small clusters when this bug is present. Once the fix was applied, the flush after restart only took a few seconds, if at all.