[MC-168748] Rapid cod spawning and despawning causing performance issues

Similar to MC-134696 but I was told to create a new issue.

The bug

Cods can rapidly spawn and despawn. They don't respect their cap. This can cause 400+ cods to spawn, dropping the server performance.

This happens more regularly when moving into unloaded chunks, but this is not always required. After a minute the numbers go back down. I printed the number of cods in chat every 10 seconds and attached a screenshot with the results.

How to reproduce

Load chunks near an ocean where cods spawn.
Cods should start spawning immediately.
/execute if entity @e[type=cod] shows how many cods are loaded. In my testing this could be as high as 500 entities.
Notice the server performance has dropped significantly.

Linked issues

is duplicated by 1

MC-167754 Fish Causes Massive Server Resource Spike Resolved

Attachments

profile-results-2019-12-24_13.12.17.txt

Comments 3

NeunEinser 2019-12-24T23:15:23Z

It's pretty interesting. /kill @e[type=!player] while being at an ocean and then doing /execute if @e[type=cod] -> over 600 entities.
Sit around for a while, most of them despawned, only 29 left for me.
Moving around might spawn enormous amounts again.

violine1101 2020-03-04T16:51:25Z

From the 20w10a changelog:

Fish now despawn when further than 64 blocks away from the closest player

So, this should be fixed now?

Misode 2020-03-04T21:49:47Z

It does indeed appear that fish spawning is much more stable now. I can still get 110+ cods spawning, this may be acceptable. The number of cod also stabilizes after a while instead of fluctuating drastically.

So I'd say that this is fixed.