Bad Practices

These bad practices should be avoided, as they can lead to memory leaks (OutOfMemoryError), lag or inconsistencies.

Storing References

Some instances such as

• DataHolder

• TileEntity

• CommandSource

• Entity

• Player

• Subject

• World

• and containers that MIGHT contain any of the above elements, including

  • Collections

  • Maps

should NEVER be stored or cached in plugins.

These are the main reasons for this:

• The references prevent proper garbage collection

• The instances might no longer be valid

This can easily be avoided by using the corresponding snapshots or saving the UUID of the given instances and requesting a live instance when you need it.

IO on the main thread

Executing some IO operations such as loading a config/data file or checking for updates/connecting to a website takes much time and greatly affects the TPS on the server. Such tasks should be done either in their own threads, or using the inbuilt scheduler’s async feature. However, it is perfectly fine to load required files/config on the main thread during server startup/plugin initialization.

this.game.getScheduler().createAsyncExecutor(this).execute(this::checkForUpdates);

For more details refer to the scheduler docs.

If this is done incorrectly, you may see clients time out, or the watchdog may even kill the server.

Accessing game objects outside the main thread

Accessing game objects outside of the main thread can lead to crashes, inconsistencies and various other problems and should be avoided. If you have a lengthy operation on a different thread use the scheduler to make changes to such game objects on the main thread. If you want to use a game object in a different thread use a snapshot of the instance or a detached data container.

Avvertimento

If this is done wrong, you can get a ConcurrentModificationException with or without a server crash at best and a corrupted player/world/server at worst.