Feature: add experimental flag to use the mcutils library for pings

README.md

@@ -46,6 +46,13 @@ docker run -it --rm itzg/mc-monitor status-bedrock --host play.fallentech.io
 
 where exit code will be 0 for success or 1 for failure.
 
+### Workarounds for some status errors
+
+Some Forge servers may cause a `string length out of bounds` error during status messages due to how the [FML2 protocol](https://wiki.vg/Minecraft_Forge_Handshake#FML2_protocol_.281.13_-_Current.29) bundles the entire modlist for client compatibility check. If there are issues with `status` failing when it otherwise should work, you can try out the experimental `--use-mc-utils` flag below (enables the [mcutils](https://github.com/xrjr/mcutils) protocol library):
+```
+docker run -it --rm itzg/mc-monitor status --use-mc-utils --host play.fallentech.io
+```
+
 ### Monitoring a server with Telegraf
 
 > The following example is provided in [examples/mc-monitor-telegraf](examples/mc-monitor-telegraf)

go.mod

@@ -4,33 +4,34 @@ go 1.17
 
 require (
 	github.com/Raqbit/mc-pinger v0.2.2
+	github.com/avast/retry-go v3.0.0+incompatible
+	github.com/google/subcommands v1.2.0
+	github.com/itzg/go-flagsfiller v1.5.0
+	github.com/itzg/line-protocol-sender v0.1.1
+	github.com/itzg/zapconfigs v0.1.0
+	github.com/prometheus/client_golang v1.11.0
+	github.com/sandertv/go-raknet v1.10.0
+	github.com/stretchr/testify v1.7.0
+	github.com/xrjr/mcutils v1.3.2
+	go.uber.org/zap v1.19.1
+)
+
+require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.1 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
-	github.com/google/subcommands v1.2.0
 	github.com/iancoleman/strcase v0.1.3 // indirect
 	github.com/influxdata/line-protocol v0.0.0-20210311194329-9aa0e372d097 // indirect
-	github.com/itzg/go-flagsfiller v1.5.0
-	github.com/itzg/line-protocol-sender v0.1.1
-	github.com/itzg/zapconfigs v0.1.0
 	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
 	github.com/pires/go-proxyproto v0.6.0 // indirect
-	github.com/prometheus/client_golang v1.11.0
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_model v0.2.0 // indirect
 	github.com/prometheus/common v0.26.0 // indirect
 	github.com/prometheus/procfs v0.6.0 // indirect
-	github.com/sandertv/go-raknet v1.10.0
-	github.com/stretchr/testify v1.7.0
 	go.uber.org/atomic v1.7.0 // indirect
 	go.uber.org/multierr v1.6.0 // indirect
-	go.uber.org/zap v1.19.1
 	golang.org/x/sys v0.0.0-20210603081109-ebe580a85c40 // indirect
 	google.golang.org/protobuf v1.26.0 // indirect
-)
-
-require (
-	github.com/avast/retry-go v3.0.0+incompatible // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

go.sum

@@ -125,6 +125,8 @@ github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UV
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/xrjr/mcutils v1.3.2 h1:AApQqiVrzNhXyggMIjW82x0EWzsQf4MTRtM0ebFjJ9E=
+github.com/xrjr/mcutils v1.3.2/go.mod h1:43n8cyMIHYjiRM2LFZLVH5Ppz2+RvWppz6OgkLP8Lsk=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
 go.uber.org/atomic v1.7.0 h1:ADUqmZGgLDDfbSL9ZmPxKTybcoEYHgpYfELNoN+7hsw=

java_status.go

@@ -15,13 +15,15 @@ import (
 	mcpinger "github.com/Raqbit/mc-pinger"
 	"github.com/google/subcommands"
 	"github.com/itzg/go-flagsfiller"
+	"github.com/xrjr/mcutils/pkg/ping"
 )
 
 type statusCmd struct {
 	Host string `default:"localhost" usage:"hostname of the Minecraft server" env:"MC_HOST"`
 	Port int    `default:"25565" usage:"port of the Minecraft server" env:"MC_PORT"`
 
 	UseServerListPing bool `usage:"indicates the legacy, server list ping should be used for pre-1.12"`
+	UseMcUtils        bool `usage:"(experimental) try using mcutils to query the server"`
 
 	RetryInterval time.Duration `usage:"if retry-limit is non-zero, status will be retried at this interval" default:"10s"`
 	RetryLimit    int           `usage:"if non-zero, failed status will be retried this many times before exiting"`
@@ -60,6 +62,10 @@ func (c *statusCmd) Execute(ctx context.Context, fs *flag.FlagSet, args ...inter
 		return c.ExecuteServerListPing()
 	}
 
+	if c.UseMcUtils {
+		return c.ExecuteMcUtilPing(logger)
+	}
+
 	var options []mcpinger.McPingerOption
 	if c.Timeout > 0 {
 		options = append(options, mcpinger.WithTimeout(c.Timeout))
@@ -143,3 +149,51 @@ func (c *statusCmd) ExecuteServerListPing() subcommands.ExitStatus {
 	// regular output is within Do function
 	return subcommands.ExitSuccess
 }
+
+func (c *statusCmd) ExecuteMcUtilPing(logger *zap.Logger) subcommands.ExitStatus {
+	client := ping.NewClient(c.Host, c.Port)
+	client.DialTimeout = c.Timeout
+	client.ReadTimeout = c.Timeout
+
+	err := retry.Do(func() error {
+
+		err := client.Connect()
+		if err != nil {
+			logger.Debug("Client failed to connect", zap.Error(err))
+			return err
+		}
+
+		defer client.Disconnect()
+
+		hs, err := client.Handshake()
+		if err != nil {
+			logger.Debug("Client failed to handshake", zap.Error(err))
+			return err
+		}
+
+		response := hs.Properties.Infos()
+		logger.Debug("mcutils ping returned", zap.Any("properties", response))
+
+		if response.Players.Max == 0 {
+			return errors.New("server not ready")
+		}
+
+		if c.ShowPlayerCount {
+			fmt.Printf("%d\n", response.Players.Online)
+		} else {
+			fmt.Printf("%s:%d : version=%s online=%d max=%d motd='%s'\n",
+				c.Host, c.Port,
+				response.Version.Name, response.Players.Online, response.Players.Max, response.Description)
+		}
+
+		return nil
+	}, retry.Delay(c.RetryInterval), retry.Attempts(uint(c.RetryLimit+1)))
+
+	if err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "failed to ping %s:%d : %s", c.Host, c.Port, err)
+		return subcommands.ExitFailure
+	}
+
+	// regular output is within Do function
+	return subcommands.ExitSuccess
+}