Add basic load balancing (server groups)

README.md

@@ -69,6 +69,21 @@ Leave this empty to require no special privilege. Note that this only affects th
 players can still be connected to this server if it is the default server, a minetest server requests it
 or if a different command is used.
 ```
+> `groups`
+```
+Type: Dictionary
+Description: List of all server groups
+```
+> `groups.*`
+```
+Type: List
+Description: Contains server group members
+```
+> `group_privs`
+```
+Type: Dictionary
+Description: List of all server groups and the required privilege (on the proxy), can be omitted
+```
 > `default_server`
 ```
 Type: String

conn.go

@@ -191,3 +191,14 @@ func ConnCount() int {
 
 	return connectedConns
 }
+
+// ConnsServer returns the client Conns that are connected to a server
+func ConnsServer(server string) []*Conn {
+	var r []*Conn
+	for _, c := range Conns() {
+		if c.ServerName() == server {
+			r = append(r, c)
+		}
+	}
+	return r
+}

igutils.go

@@ -162,6 +162,7 @@ func init() {
 				c.SendChatMsg("Current server: " + c.ServerName() + " | All servers: " + r)
 			} else {
 				servers := ConfKey("servers").(map[interface{}]interface{})
+				groups := ConfKey("groups").(map[interface{}]interface{})
 				srv := c.ServerName()
 
 				if srv == param {
@@ -169,17 +170,35 @@ func init() {
 					return
 				}
 
-				if servers[param] == nil {
+				nogrp := true
+				for grp := range groups {
+					name, ok := grp.(string)
+					if !ok {
+						continue
+					}
+
+					if name == param {
+						nogrp = false
+					}
+				}
+
+				if servers[param] == nil && nogrp {
 					c.SendChatMsg("Unknown servername " + param)
 					return
 				}
 
 				reqprivs := make(map[string]bool)
+
 				reqpriv, ok := ConfKey("servers:" + param + ":priv").(string)
 				if ok {
 					reqprivs[reqpriv] = true
 				}
 
+				reqpriv, ok = ConfKey("group_privs:" + param).(string)
+				if ok {
+					reqprivs[reqpriv] = true
+				}
+
 				allow, err := c.CheckPrivs(reqprivs)
 				if err != nil {
 					log.Print(err)

media.go

@@ -10,7 +10,6 @@ import (
 	"net"
 	"os"
 	"strings"
-	"sync"
 
 	"github.com/anon55555/mt/rudp"
 )
@@ -362,8 +361,6 @@ func loadMedia(servers map[string]struct{}) {
 
 	loadMediaCache()
 
-	var wg sync.WaitGroup
-
 	for server := range servers {
 		straddr := ConfKey("servers:" + server + ":address")
 
@@ -383,23 +380,15 @@ func loadMedia(servers map[string]struct{}) {
 			continue
 		}
 
-		wg.Add(1)
-
 		clt := &Conn{username: "media"}
 
 		fin := make(chan *Conn) // close-only
 		go Init(clt, srv, false, true, fin)
+		<-fin
 
-		go func() {
-			<-fin
-
-			srv.fetchMedia()
-			wg.Done()
-		}()
+		srv.fetchMedia()
 	}
 
-	wg.Wait()
-
 	if err := mergeNodedefs(nodedefs); err != nil {
 		log.Fatal(err)
 	}

redirect.go

@@ -20,8 +20,8 @@ func RegisterOnRedirectDone(function func(*Conn, string, bool)) {
 	onRedirectDone = append(onRedirectDone, function)
 }
 
-func processRedirectDone(c *Conn, newsrv string) {
-	success := c.ServerName() == newsrv
+func processRedirectDone(c *Conn, newsrv *string) {
+	success := c.ServerName() == *newsrv
 
 	successstr := "false"
 	if success {
@@ -30,12 +30,12 @@ func processRedirectDone(c *Conn, newsrv string) {
 
 	rpcSrvMu.Lock()
 	for srv := range rpcSrvs {
-		srv.doRpc("->REDIRECTED "+c.Username()+" "+newsrv+" "+successstr, "--")
+		srv.doRpc("->REDIRECTED "+c.Username()+" "+*newsrv+" "+successstr, "--")
 	}
 	rpcSrvMu.Unlock()
 
 	for i := range onRedirectDone {
-		onRedirectDone[i](c, newsrv, success)
+		onRedirectDone[i](c, *newsrv, success)
 	}
 }
 
@@ -44,11 +44,32 @@ func (c *Conn) Redirect(newsrv string) error {
 	c.redirectMu.Lock()
 	defer c.redirectMu.Unlock()
 
-	defer processRedirectDone(c, newsrv)
+	defer processRedirectDone(c, &newsrv)
 
 	straddr, ok := ConfKey("servers:" + newsrv + ":address").(string)
 	if !ok {
-		return fmt.Errorf("server %s does not exist", newsrv)
+		grp, ok := ConfKey("groups:" + newsrv).([]interface{})
+		if !ok {
+			return fmt.Errorf("server or group %s does not exist", newsrv)
+		}
+
+		smallestCnt := int(^uint(0) >> 1)
+		for _, srv := range grp {
+			cnt := len(ConnsServer(srv.(string)))
+			if cnt < smallestCnt {
+				if c.ServerName() == srv.(string) {
+					return fmt.Errorf("already connected to server %s", srv.(string))
+				}
+
+				smallestCnt = cnt
+				newsrv = srv.(string)
+			}
+		}
+
+		straddr, ok = ConfKey("servers:" + newsrv + ":address").(string)
+		if !ok {
+			return fmt.Errorf("server %s does not exist", newsrv)
+		}
 	}
 
 	if c.ServerName() == newsrv {
@@ -70,7 +91,7 @@ func (c *Conn) Redirect(newsrv string) error {
 		return err
 	}
 
-	fin := make(chan *Conn) // close-only
+	fin := make(chan *Conn)
 	go Init(c, srv, true, false, fin)
 	initOk := <-fin
 

storage.go

@@ -17,7 +17,7 @@ func initStorageDB() (*sql.DB, error) {
 	}
 
 	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS storage (
-		key VARCHAR(512) NOT NULL,
+		key VARCHAR(512) PRIMARY KEY NOT NULL,
 		value VARCHAR(512) NOT NULL
 	);`); err != nil {
 		db.Close()