From e29789114cfd79a741a7117da170018ce1a3f113 Mon Sep 17 00:00:00 2001
From: Dane Everitt <dane@daneeveritt.com>
Date: Sun, 11 Oct 2020 15:02:37 -0700
Subject: [PATCH] Fix server disk usage not being reported properly; closes
 pterodactyl/panel#2445

---
 server/filesystem/disk_space.go | 10 ++++++++++
 server/resources.go             | 26 +++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/server/filesystem/disk_space.go b/server/filesystem/disk_space.go
index 4922b7a..3c7ef79 100644
--- a/server/filesystem/disk_space.go
+++ b/server/filesystem/disk_space.go
@@ -75,6 +75,16 @@ func (fs *Filesystem) HasSpaceAvailable(allowStaleValue bool) bool {
 	return size <= fs.MaxDisk()
 }
 
+// Returns the cached value for the amount of disk space used by the filesystem. Do not rely on this
+// function for critical logical checks. It should only be used in areas where the actual disk usage
+// does not need to be perfect, e.g. API responses for server resource usage.
+func (fs *Filesystem) CachedUsage() int64 {
+	fs.mu.RLock()
+	defer fs.mu.RUnlock()
+
+	return fs.diskUsed
+}
+
 // Internal helper function to allow other parts of the codebase to check the total used disk space
 // as needed without overly taxing the system. This will prioritize the value from the cache to avoid
 // excessive IO usage. We will only walk the filesystem and determine the size of the directory if there
diff --git a/server/resources.go b/server/resources.go
index db7bea8..d3a3d2c 100644
--- a/server/resources.go
+++ b/server/resources.go
@@ -1,6 +1,7 @@
 package server
 
 import (
+	"encoding/json"
 	"github.com/pterodactyl/wings/environment"
 	"sync"
 )
@@ -17,17 +18,34 @@ type ResourceUsage struct {
 	// The current server status.
 	State string `json:"state" default:"offline"`
 
-	// The current disk space being used by the server. This is cached to prevent slow lookup
-	// issues on frequent refreshes.
+	// The current disk space being used by the server. This value is not guaranteed to be accurate
+	// at all times. It is "manually" set whenever server.Proc() is called. This is kind of just a
+	// hacky solution for now to avoid passing events all over the place.
 	Disk int64 `json:"disk_bytes"`
 }
 
+// Alias the resource usage so that we don't infinitely recurse when marshaling the struct.
+type IResourceUsage ResourceUsage
+
+// Custom marshaler to ensure that the object is locked when we're converting it to JSON in
+// order to avoid race conditions.
+func (ru *ResourceUsage) MarshalJSON() ([]byte, error) {
+	ru.mu.Lock()
+	defer ru.mu.Unlock()
+
+	return json.Marshal(IResourceUsage(*ru))
+}
+
 // Returns the resource usage stats for the server instance. If the server is not running, only the
 // disk space currently used will be returned. When the server is running all of the other stats will
 // be returned.
 //
 // When a process is stopped all of the stats are zeroed out except for the disk.
 func (s *Server) Proc() *ResourceUsage {
+	s.resources.SetDisk(s.Filesystem().CachedUsage())
+
+	// Get a read lock on the resources at this point. Don't do this before setting
+	// the disk, otherwise you'll cause a deadlock.
 	s.resources.mu.RLock()
 	defer s.resources.mu.RUnlock()
 
@@ -35,11 +53,9 @@ func (s *Server) Proc() *ResourceUsage {
 }
 
 func (s *Server) emitProcUsage() {
-	s.resources.mu.RLock()
-	if err := s.Events().PublishJson(StatsEvent, s.resources); err != nil {
+	if err := s.Events().PublishJson(StatsEvent, s.Proc()); err != nil {
 		s.Log().WithField("error", err).Warn("error while emitting server resource usage to listeners")
 	}
-	s.resources.mu.RUnlock()
 }
 
 // Returns the servers current state.