feat: add page for Velocity's system properties (#466)

feat: add draft design for Velocity env variables page

style: fix formatting issues

fix: correct spelling errors

refactor(design): implement changes suggested in Discord & reviews

Discord suggestion can be found here: https://discord.com/channels/289587909051416579/947676006964162611/1273324897158037607

fix: add missing period

refactor(design): update properties design to match Paper's design

This (as mentioned in Discord) allows for links to specific properties

fix: correctly capitalize Vanilla

Co-authored-by: Matouš Kučera <[email protected]>

fix: correctly capitalize Vanilla (2)

Co-authored-by: Matouš Kučera <[email protected]>

update: improve descriptions for some properties

config/sidebar.velocity.ts

@@ -47,6 +47,7 @@ const velocity: SidebarsConfig = {
           },
           items: [
             "admin/reference/configuration",
+            "admin/reference/system-properties",
             "admin/reference/commands",
             "admin/reference/server-compatibility",
             "admin/reference/comparison",

docs/velocity/admin/reference/system-properties.md

@@ -0,0 +1,92 @@
+---
+slug: /reference/system-properties
+description: Documentation for the system properties Velocity may check.
+---
+
+# Velocity System Properties
+
+These system properties can be set when you start your server allowing for the configuration of various settings.
+
+:::danger[Danger Ahead]
+
+Setting flags for the JVM can alter how it operates and the same goes for the Velocity server.
+If you are unsure about what a flag does, it is recommended that you **do not use it**.
+
+:::
+
+## How they work
+
+System properties are set when you start your server. For example, if you are using a `.bat` or a `.sh` file to start your server, you can add the system properties to
+the file. For example:
+
+```bash
+java -Dvelocity.packet-decode-logging=true -jar velocity.jar
+```
+
+:::info
+
+Some of Velocity's system properties contain a `.` character in their name. When using PowerShell, these will require wrapping in quotes.
+i.e. `"-Dvelocity.packet-decode-logging=true"`
+
+:::
+
+Where a `-D` is used to set a system property, and the system property is `velocity.packet-decode-logging` with a value of `true`.
+Otherwise, just add them to the start command.
+
+:::note
+
+The default value shown may not be set for the property but will only be used by Velocity if it is not explicitly set.
+
+:::
+
+## List of system properties
+
+#### auth.forceSecureProfiles:
+
+- **default**: `true`
+- **description**: Overrides `force-key-authentication` from the config. If not set, it will be automatically set to the current config value.
+
+#### velocity.natives-tmpdir:
+
+- **default**: `unset`
+- **description**: Temporary directory for Velocity native files. (If set, it will also define `io.netty.native.workdir`)
+
+#### velocity.max-known-packs:
+
+- **default**: `64`
+- **description**: Limits known packs to the Vanilla default to prevent crashing Velocity.
+
+#### velocity.max-packets-per-flush:
+
+- **default**: `8192`
+- **description**: The max amount of packets before the queue is flushed automatically.
+
+#### velocity.log-server-backpressure:
+
+- **default**: `false`
+- **description**: Whether Velocity should log if the server connection is writable and thus if the player connection will be auto-read.
+
+#### velocity.packet-decode-logging:
+
+- **default**: `false`
+- **description**: Whether packet decoding errors should be logged extensively.
+
+#### velocity.increased-compression-cap:
+
+- **default**: `false`
+- **description**: Whether the maximum uncompressed packet size should be set to its maximum supported limit (128 MiB) instead of the Vanilla limit (8 MiB).
+
+#### velocity.disable-native-transport:
+
+- **default**: `false`
+- **description**: Whether to disable Netty's native transport methods like Epoll. If set to true, Velocity will use Java's NIO transport instead.
+
+#### velocity.natives-disabled:
+
+- **default**: `false`
+- **description**: Whether native functionality for specific operating systems should be disabled.
+
+#### velocity.strictErrorHandling:
+
+- **default**: `true`
+- **description**: Whether the client should disconnect on packet errors. Temporarily added in MC 1.20.5 to help modded servers transition to this change.