From 1892b270b1012f2353baa0d72e77e1f40a3adb57 Mon Sep 17 00:00:00 2001
From: Matthew Penner <me@matthewp.io>
Date: Mon, 17 Jan 2022 20:20:30 -0700
Subject: [PATCH] environment: allow overriding memory overhead; closes
 pterodactyl/panel#3728 (#111)

---
 config/config_docker.go | 74 ++++++++++++++++++++++++++++++++++++++---
 environment/settings.go |  8 +----
 2 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/config/config_docker.go b/config/config_docker.go
index 33e40a4..7fd2034 100644
--- a/config/config_docker.go
+++ b/config/config_docker.go
@@ -3,6 +3,7 @@ package config
 import (
 	"encoding/base64"
 	"encoding/json"
+	"sort"
 
 	"github.com/docker/docker/api/types"
 )
@@ -51,9 +52,9 @@ type DockerConfiguration struct {
 	// Registries .
 	Registries map[string]RegistryConfiguration `json:"registries" yaml:"registries"`
 
-	// The size of the /tmp directory when mounted into a container. Please be aware that Docker
-	// utilizes host memory for this value, and that we do not keep track of the space used here
-	// so avoid allocating too much to a server.
+	// TmpfsSize specifies the size for the /tmp directory mounted into containers. Please be
+	// aware that Docker utilizes the host's system memory for this value, and that we do not
+	// keep track of the space used there, so avoid allocating too much to a server.
 	TmpfsSize uint `default:"100" json:"tmpfs_size" yaml:"tmpfs_size"`
 
 	// ContainerPidLimit sets the total number of processes that can be active in a container
@@ -62,14 +63,18 @@ type DockerConfiguration struct {
 	// available pids and crash.
 	ContainerPidLimit int64 `default:"512" json:"container_pid_limit" yaml:"container_pid_limit"`
 
-	// InstallLimits defines the limits on the installer containers that prevents a server's
+	// InstallerLimits defines the limits on the installer containers that prevents a server's
 	// installation process from unintentionally consuming more resources than expected. This
 	// is used in conjunction with the server's defined limits. Whichever value is higher will
-	// take precedence in the install containers.
+	// take precedence in the installer containers.
 	InstallerLimits struct {
 		Memory int64 `default:"1024" json:"memory" yaml:"memory"`
 		Cpu    int64 `default:"100" json:"cpu" yaml:"cpu"`
 	} `json:"installer_limits" yaml:"installer_limits"`
+
+	// Overhead controls the memory overhead given to all containers to circumvent certain
+	// software such as the JVM not staying below the maximum memory limit.
+	Overhead Overhead `json:"overhead" yaml:"overhead"`
 }
 
 // RegistryConfiguration defines the authentication credentials for a given
@@ -91,3 +96,62 @@ func (c RegistryConfiguration) Base64() (string, error) {
 	}
 	return base64.URLEncoding.EncodeToString(b), nil
 }
+
+// Overhead controls the memory overhead given to all containers to circumvent certain
+// software such as the JVM not staying below the maximum memory limit.
+type Overhead struct {
+	// Override controls if the overhead limits should be overridden by the values in the config file.
+	Override bool `default:"false" json:"override" yaml:"override"`
+
+	// DefaultMultiplier sets the default multiplier for if no Multipliers are able to be applied.
+	DefaultMultiplier float64 `default:"1.05" json:"default_multiplier" yaml:"default_multiplier"`
+
+	// Multipliers allows overriding DefaultMultiplier depending on the amount of memory
+	// configured for a server.
+	//
+	// Default values (used if Override is `false`)
+	// - Less than 2048 MB of memory, multiplier of 1.15 (15%)
+	// - Less than 4096 MB of memory, multiplier of 1.10 (10%)
+	// - Otherwise, multiplier of 1.05 (5%) - specified in DefaultMultiplier
+	//
+	// If the defaults were specified in the config they would look like:
+	// ```yaml
+	// multipliers:
+	//   2048: 1.15
+	//   4096: 1.10
+	// ```
+	Multipliers map[int]float64 `json:"multipliers" yaml:"multipliers"`
+}
+
+func (o Overhead) GetMultiplier(memoryLimit int64) float64 {
+	// Default multiplier values.
+	if !o.Override {
+		if memoryLimit <= 2048 {
+			return 1.15
+		} else if memoryLimit <= 4096 {
+			return 1.10
+		}
+		return 1.05
+	}
+
+	// This plucks the keys of the Multipliers map, so they can be sorted from
+	// smallest to largest in order to correctly apply the proper multiplier.
+	i := 0
+	multipliers := make([]int, len(o.Multipliers))
+	for k := range o.Multipliers {
+		multipliers[i] = k
+		i++
+	}
+	sort.Ints(multipliers)
+
+	// Loop through the memory values in order (smallest to largest)
+	for _, m := range multipliers {
+		// If the server's memory limit exceeds the modifier's limit, don't apply it.
+		if memoryLimit > int64(m) {
+			continue
+		}
+		return o.Multipliers[m]
+	}
+
+	return o.DefaultMultiplier
+}
diff --git a/environment/settings.go b/environment/settings.go
index 0371757..ae853cf 100644
--- a/environment/settings.go
+++ b/environment/settings.go
@@ -75,13 +75,7 @@ func (l Limits) ConvertedCpuLimit() int64 {
 // server is < 4G, use 10%, if less than 2G use 15%. This avoids unexpected
 // crashes from processes like Java which run over the limit.
 func (l Limits) MemoryOverheadMultiplier() float64 {
-	if l.MemoryLimit <= 2048 {
-		return 1.15
-	} else if l.MemoryLimit <= 4096 {
-		return 1.10
-	}
-
-	return 1.05
+	return config.Get().Docker.Overhead.GetMultiplier(l.MemoryLimit)
 }
 
 func (l Limits) BoundedMemoryLimit() int64 {