Re-implement ContainerInspect call in Wings to use more performant json encoder (#119)

* First pass at re-implementing the Docker inspect call to use more efficient json parser

* Improve logic

config/config_docker.go

@@ -75,6 +75,8 @@ type DockerConfiguration struct {
 	// 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"`
+
+	UsePerformantInspect bool `default:"true" json:"use_performant_inspect" yaml:"use_performant_inspect"`
 }
 
 // RegistryConfiguration defines the authentication credentials for a given

environment/docker/api.go

@@ -0,0 +1,116 @@
+package docker
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"reflect"
+	"strings"
+	"sync"
+
+	"emperror.dev/errors"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/versions"
+	"github.com/docker/docker/client"
+	"github.com/docker/docker/errdefs"
+	"github.com/goccy/go-json"
+	"github.com/pterodactyl/wings/config"
+)
+
+var (
+	o           sync.Once
+	cli         cliSettings
+	fastEnabled bool
+)
+
+type cliSettings struct {
+	enabled bool
+	proto   string
+	host    string
+	scheme  string
+	version string
+}
+
+func configure(c *client.Client) {
+	o.Do(func() {
+		fastEnabled = config.Get().Docker.UsePerformantInspect
+
+		r := reflect.ValueOf(c).Elem()
+		cli.proto = r.FieldByName("proto").String()
+		cli.host = r.FieldByName("addr").String()
+		cli.scheme = r.FieldByName("scheme").String()
+		cli.version = r.FieldByName("version").String()
+	})
+}
+
+// ContainerInspect is a rough equivalent of Docker's client.ContainerInspect()
+// but re-written to use a more performant JSON decoder. This is important since
+// a large number of requests to this endpoint are spawned by Wings, and the
+// standard "encoding/json" shows its performance woes badly even with single
+// containers running.
+func (e *Environment) ContainerInspect(ctx context.Context) (types.ContainerJSON, error) {
+	configure(e.client)
+
+	// Support feature flagging of this functionality so that if something goes
+	// wrong for now it is easy enough for people to switch back to the older method
+	// of fetching stats.
+	if !fastEnabled {
+		return e.client.ContainerInspect(ctx, e.Id)
+	}
+
+	var st types.ContainerJSON
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "/containers/"+e.Id+"/json", nil)
+	if err != nil {
+		return st, errors.WithStack(err)
+	}
+
+	if cli.proto == "unix" || cli.proto == "npipe" {
+		req.Host = "docker"
+	}
+
+	req.URL.Host = cli.host
+	req.URL.Scheme = cli.scheme
+
+	res, err := e.client.HTTPClient().Do(req)
+	if err != nil {
+		return st, errdefs.FromStatusCode(err, res.StatusCode)
+	}
+
+	body, err := io.ReadAll(res.Body)
+	if err != nil {
+		return st, errors.Wrap(err, "failed to read response body from Docker")
+	}
+	if err := parseErrorFromResponse(res, body); err != nil {
+		return st, errdefs.FromStatusCode(err, res.StatusCode)
+	}
+	if err := json.Unmarshal(body, &st); err != nil {
+		return st, errors.WithStack(err)
+	}
+	return st, nil
+}
+
+// parseErrorFromResponse is a re-implementation of Docker's
+// client.checkResponseErr() function.
+func parseErrorFromResponse(res *http.Response, body []byte) error {
+	if res.StatusCode >= 200 && res.StatusCode < 400 {
+		return nil
+	}
+
+	var ct string
+	if res.Header != nil {
+		ct = res.Header.Get("Content-Type")
+	}
+
+	var emsg string
+	if (cli.version == "" || versions.GreaterThan(cli.version, "1.23")) && ct == "application/json" {
+		var errResp types.ErrorResponse
+		if err := json.Unmarshal(body, &errResp); err != nil {
+			return errors.WithStack(err)
+		}
+		emsg = strings.TrimSpace(errResp.Message)
+	} else {
+		emsg = strings.TrimSpace(string(body))
+	}
+
+	return errors.Wrap(errors.New(emsg), "Error response from daemon")
+}

environment/docker/container.go

@@ -118,7 +118,7 @@ func (e *Environment) InSituUpdate() error {
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
 	defer cancel()
 
-	if _, err := e.client.ContainerInspect(ctx, e.Id); err != nil {
+	if _, err := e.ContainerInspect(ctx); err != nil {
 		// If the container doesn't exist for some reason there really isn't anything
 		// we can do to fix that in this process (it doesn't make sense at least). In those
 		// cases just return without doing anything since we still want to save the configuration
@@ -150,7 +150,7 @@ func (e *Environment) Create() error {
 	// If the container already exists don't hit the user with an error, just return
 	// the current information about it which is what we would do when creating the
 	// container anyways.
-	if _, err := e.client.ContainerInspect(context.Background(), e.Id); err == nil {
+	if _, err := e.ContainerInspect(context.Background()); err == nil {
 		return nil
 	} else if !client.IsErrNotFound(err) {
 		return errors.Wrap(err, "environment/docker: failed to inspect container")

environment/docker/environment.go

@@ -10,7 +10,6 @@ import (
 	"github.com/apex/log"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/client"
-
 	"github.com/pterodactyl/wings/environment"
 	"github.com/pterodactyl/wings/events"
 	"github.com/pterodactyl/wings/remote"
@@ -116,7 +115,7 @@ func (e *Environment) Events() *events.Bus {
 // will work fine when using the container name as the lookup parameter in addition to the longer
 // ID auto-assigned when the container is created.
 func (e *Environment) Exists() (bool, error) {
-	_, err := e.client.ContainerInspect(context.Background(), e.Id)
+	_, err := e.ContainerInspect(context.Background())
 	if err != nil {
 		// If this error is because the container instance wasn't found via Docker we
 		// can safely ignore the error and just return false.
@@ -140,7 +139,7 @@ func (e *Environment) Exists() (bool, error) {
 //
 // @see docker/client/errors.go
 func (e *Environment) IsRunning(ctx context.Context) (bool, error) {
-	c, err := e.client.ContainerInspect(ctx, e.Id)
+	c, err := e.ContainerInspect(ctx)
 	if err != nil {
 		return false, err
 	}
@@ -150,7 +149,7 @@ func (e *Environment) IsRunning(ctx context.Context) (bool, error) {
 // Determine the container exit state and return the exit code and whether or not
 // the container was killed by the OOM killer.
 func (e *Environment) ExitState() (uint32, bool, error) {
-	c, err := e.client.ContainerInspect(context.Background(), e.Id)
+	c, err := e.ContainerInspect(context.Background())
 	if err != nil {
 		// I'm not entirely sure how this can happen to be honest. I tried deleting a
 		// container _while_ a server was running and wings gracefully saw the crash and

environment/docker/power.go

@@ -66,7 +66,7 @@ func (e *Environment) Start(ctx context.Context) error {
 		}
 	}()
 
-	if c, err := e.client.ContainerInspect(ctx, e.Id); err != nil {
+	if c, err := e.ContainerInspect(ctx); err != nil {
 		// Do nothing if the container is not found, we just don't want to continue
 		// to the next block of code here. This check was inlined here to guard against
 		// a nil-pointer when checking c.State below.
@@ -235,7 +235,7 @@ func (e *Environment) WaitForStop(seconds uint, terminate bool) error {
 
 // Terminate forcefully terminates the container using the signal provided.
 func (e *Environment) Terminate(signal os.Signal) error {
-	c, err := e.client.ContainerInspect(context.Background(), e.Id)
+	c, err := e.ContainerInspect(context.Background())
 	if err != nil {
 		// Treat missing containers as an okay error state, means it is obviously
 		// already terminated at this point.

environment/docker/stats.go

@@ -16,7 +16,7 @@ import (
 // Uptime returns the current uptime of the container in milliseconds. If the
 // container is not currently running this will return 0.
 func (e *Environment) Uptime(ctx context.Context) (int64, error) {
-	ins, err := e.client.ContainerInspect(ctx, e.Id)
+	ins, err := e.ContainerInspect(ctx)
 	if err != nil {
 		return 0, errors.Wrap(err, "environment: could not inspect container")
 	}