This is a pregen alternative for when other pregen mods/plugins may just not fit your needs.
You can give this mod a try if other pregens left you with a boot/kill-loop, I personally use this with Lithosphere which is too heavy for my 5gb ram server to pregen using other mods.

Attributes:

tries to generate a chunk per tick
slows down pregen down if the server is running under 1000ms per second
nice spammy console message each 20 ticks with status
no fancy algorithm, this generates lines like a printer prints on paper
caches which chunks it tried to pregen at least once, so they get skipped next time
skips up to 128 chunks per tick
saves every 16 chunks current progress
currently only overworld pregen is supported
do not misunderstand, this mod may still cause the server to quit, just less frequently

Planned

config for all the static values
a command to adjust everything ingame

Usage

After first boot a file called /world/yacp/task.json should be generated.
Stop the server to edit it (in case you don't, it does get overriden on stopping the server).
The Start and End coordinates are in chunk units (not block units!).
Start should always be a lower value than End!
If you want to start a new task, set the value of At to the same as Start and change Complete to false.
Processed and Existing are just last session's stats.

Known Issues

After the pregen and afterwards enabling bluemap, I noticed some chunks have been missing (black spots that wouldn't become a map preview).
Solution: remove all .yacp cache files and run the pregen again.
It will be far faster this time because most chunks exists already and server load should be minimal.

Discord

https://discord.gg/AkMAzaA

Yet Another Chunk Pregen