add linter and flag for enabling resource constraints

.golangci.yml

@@ -0,0 +1,22 @@
+linters:
+  disable-all: true
+  enable:
+    - errcheck
+    - goconst
+    - gocyclo
+    - gofmt
+    - goimports
+    - gosec
+    - govet
+    - ineffassign
+    - lll
+    - misspell
+    - nakedret
+    - prealloc
+    - staticcheck
+    - typecheck
+    - unconvert
+    - unparam
+    - unused
+    - whitespace
+  fast: false

README.md

@@ -71,13 +71,22 @@ To start the server, run the following command:
 ```sh
 ./server
 ```
-The default directory where the code files will be stored is `/tmp/`
-A separate directory is created for every language.
-To change the directory where the code files will be stored(eventually removed by the garbage collector), use
+
+### Flags
+- `--code-dir`
+    The default directory where the code files will be stored is `/tmp/`
+    A separate directory is created for every language.
+    To change the directory where the code files will be stored(eventually removed by the garbage collector), use
 ```sh
 ./server --code-dir /path/to/code/dir
 ```
 
+- `--resource-constraints`
+    By default, resource constraints are turned off to improve the performance, if you want to enable it, use
+```sh
+./server --resource-constraints true
+```
+
 ## API
 
 ### Submit Code

cmd/flags.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"flag"
+	"remote-code-engine/pkg/config"
+
+	"go.uber.org/zap"
+)
+
+func ParseFlags() {
+	flag.StringVar(&config.BaseCodePath, "code-dir", "/tmp/", "Base path to store the code files")
+	flag.BoolVar(&config.ResourceConstraints, "resource-constraints", false, "Enable resource constraints (default false)")
+	help := flag.Bool("help", false, "Display help")
+
+	flag.Parse()
+
+	if *help {
+		flag.Usage()
+		return
+	}
+
+	logger.Info("parsed the flags",
+		zap.String("code-dir", config.BaseCodePath),
+		zap.Bool("resource-constraints", config.ResourceConstraints),
+	)
+}

cmd/server.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"flag"
 	"net/http"
 	"os"
 	"remote-code-engine/pkg/config"
@@ -55,10 +54,11 @@ func setupCodeDirectory(imageConfig config.ImageConfig) {
 }
 
 func main() {
-	defer logger.Sync()
+	defer func() {
+		_ = logger.Sync()
+	}()
 
-	flag.StringVar(&config.BaseCodePath, "code-dir", "/tmp/", "Base path to store the code files")
-	flag.Parse()
+	ParseFlags()
 
 	// This should be given as a command line argument.
 	imageConfig, err := config.LoadConfig("../config.yml")
@@ -83,7 +83,23 @@ func main() {
 		panic(err)
 	}
 
-	go cli.FreeUpZombieContainers(context.Background())
+	ctx, cancel := context.WithCancel(context.Background())
 
-	StartServer(cli, imageConfig)
+	go func() {
+		err = cli.FreeUpZombieContainers(ctx)
+		if err != nil {
+			logger.Error("failed to free up zombie containers",
+				zap.Error(err),
+			)
+		}
+	}()
+
+	err = StartServer(cli, imageConfig)
+	if err != nil {
+		logger.Error("failed to start the server",
+			zap.Error(err),
+		)
+		cancel()
+		panic(err)
+	}
 }

pkg/config/config.go

@@ -17,7 +17,8 @@ const (
 )
 
 var (
-	BaseCodePath string
+	BaseCodePath        string
+	ResourceConstraints bool
 )
 
 type LanguageConfig struct {
@@ -55,3 +56,7 @@ func (c *ImageConfig) IsLanguageSupported(lang Language) bool {
 func GetHostLanguageCodePath(lang Language) string {
 	return filepath.Join(BaseCodePath, string(lang))
 }
+
+func IsResourceConstraintsEnabled() bool {
+	return ResourceConstraints
+}

pkg/config/config_test.go

@@ -34,7 +34,7 @@ func TestLoadConfig(t *testing.T) {
 
 	// Write the sample config to a temporary file
 	configPath := filepath.Join(tempDir, "config.yaml")
-	err = os.WriteFile(configPath, data, 0644)
+	err = os.WriteFile(configPath, data, 0600)
 	if err != nil {
 		t.Fatalf("failed to write sample config to file: %v", err)
 	}

pkg/container/consts.go

@@ -5,7 +5,7 @@ import "time"
 const (
 	MAX_EXECUTION_TIME = 60 * time.Second
 
-	// The server running this will check for every 10 minutes whether there are zombie containers - completed containers and removes them.
+	// The server running this will check for every 10 minutes whether there are zombie containers.
 	GarbageCollectionTimeWindow = 5 * time.Minute
 
 	// Path where the code files are mounted.

pkg/container/dockerclient.go

@@ -47,7 +47,7 @@ func NewDockerClient(opts *client.Opt, logger *zap.Logger) (ContainerClient, err
 }
 
 func (d *dockerClient) GetContainers(ctx context.Context, opts *container.ListOptions) ([]Container, error) {
-	var containersList []Container
+	containersList := []Container{}
 
 	containers, err := d.client.ContainerList(ctx, *opts)
 	if err != nil {
@@ -66,6 +66,39 @@ func (d *dockerClient) GetContainers(ctx context.Context, opts *container.ListOp
 	return containersList, nil
 }
 
+func (d *dockerClient) getResourceConstraints() container.Resources {
+	if config.IsResourceConstraintsEnabled() {
+		return container.Resources{
+			Memory:   500 * 1024 * 1024, // 500 MB
+			NanoCPUs: 1000000000,        // 1 CPU
+			Ulimits: []*units.Ulimit{
+				{
+					Name: "nproc",
+					Soft: 64,
+					Hard: 128,
+				},
+				{
+					Name: "nofile",
+					Soft: 64,
+					Hard: 128,
+				},
+				{
+					Name: "core",
+					Soft: 0,
+					Hard: 0,
+				},
+				{
+					// Maximum file size that can be created by the process (output file in our case)
+					Name: "fsize",
+					Soft: 20 * 1024 * 1024,
+					Hard: 20 * 1024 * 1024,
+				},
+			},
+		}
+	}
+	return container.Resources{}
+}
+
 func (d *dockerClient) ExecuteCode(ctx context.Context, code *Code) (string, error) {
 	codeFileName, inputFileName, err := createCodeAndInputFilesHost(code, d.logger)
 	if err != nil {
@@ -76,6 +109,8 @@ func (d *dockerClient) ExecuteCode(ctx context.Context, code *Code) (string, err
 		zap.String("input file name", inputFileName),
 	)
 
+	resourceConstraints := d.getResourceConstraints()
+
 	res, err := d.client.ContainerCreate(ctx, &container.Config{
 		Cmd:   getContainerCommand(code, codeFileName, inputFileName),
 		Image: code.Image,
@@ -92,40 +127,13 @@ func (d *dockerClient) ExecuteCode(ctx context.Context, code *Code) (string, err
 		RestartPolicy: container.RestartPolicy{
 			Name: "no",
 		},
-		// We are reading the container logs to get the output. So it's better to disable and have a separate thread to delete stale containers
+		// We are reading the container logs to get the output.
+		// So it's better to disable and have a separate thread to delete stale containers
 		AutoRemove: false,
 		// Drop all the capabilities
 		CapDrop:    []string{"ALL"},
 		Privileged: false,
-		// Set the memory limit to 1GB
-		Resources: container.Resources{
-			// set 500 MB as the memory limit in bytes
-			Memory:   500 * 1024 * 1024,
-			NanoCPUs: 500000000, // 0.5 CPU
-			Ulimits: []*units.Ulimit{
-				{
-					Name: "nproc",
-					Soft: 64,
-					Hard: 128,
-				},
-				{
-					Name: "nofile",
-					Soft: 64,
-					Hard: 128,
-				},
-				{
-					Name: "core",
-					Soft: 0,
-					Hard: 0,
-				},
-				{
-					// Maximum file size that can be created by the process (output file in our case)
-					Name: "fsize",
-					Soft: 20 * 1024 * 1024,
-					Hard: 20 * 1024 * 1024,
-				},
-			},
-		},
+		Resources:  resourceConstraints,
 	}, nil, nil, getContainerName())
 
 	if err != nil {
@@ -217,22 +225,36 @@ func deleteStaleFiles(dir string, logger *zap.Logger) error {
 }
 
 func (d *dockerClient) FreeUpZombieContainers(ctx context.Context) error {
+	ticker := time.NewTicker(GarbageCollectionTimeWindow)
 	for {
-		pruneResults, err := d.client.ContainersPrune(ctx, filters.Args{})
-		if err != nil {
-			d.logger.Error("failed to prune containers",
-				zap.Error(err),
-			)
-		}
+		select {
+		case <-ctx.Done():
+			d.logger.Info("stopping the zombie container cleanup routine")
+			return nil
+		case <-ticker.C:
+			pruneResults, err := d.client.ContainersPrune(ctx, filters.Args{})
+			if err != nil {
+				d.logger.Error("failed to prune containers",
+					zap.Error(err),
+				)
+			}
 
-		d.logger.Info("successfully pruned the containers:",
-			zap.Int("#Pruned containers", len(pruneResults.ContainersDeleted)),
-		)
+			d.logger.Info("successfully pruned the containers:",
+				zap.Int("#Pruned containers", len(pruneResults.ContainersDeleted)),
+			)
 
-		deleteStaleFiles(config.GetHostLanguageCodePath(config.Cpp), d.logger)
-		deleteStaleFiles(config.GetHostLanguageCodePath(config.Golang), d.logger)
+			if err = deleteStaleFiles(config.GetHostLanguageCodePath(config.Cpp), d.logger); err != nil {
+				d.logger.Error("failed to delete stale files",
+					zap.Error(err),
+				)
+			}
 
-		time.Sleep(GarbageCollectionTimeWindow)
+			if err = deleteStaleFiles(config.GetHostLanguageCodePath(config.Golang), d.logger); err != nil {
+				d.logger.Error("failed to delete stale files",
+					zap.Error(err),
+				)
+			}
+		}
 	}
 }
 

pkg/container/file-helper.go

@@ -40,7 +40,7 @@ func createFile(filePath, base64FileContent string, logger *zap.Logger) (string,
 		return filepath.Base(filePath), fmt.Errorf("failed to decode the file content: %w", err)
 	}
 
-	n, err := f.Write([]byte(data))
+	n, err := f.Write(data)
 	if err != nil {
 		return filepath.Base(filePath), fmt.Errorf("failed to write the content to the file: %w", err)
 	}

pkg/container/types.go

@@ -22,8 +22,11 @@ type Code struct {
 
 type ContainerClient interface {
 	FreeUpZombieContainers(ctx context.Context) error
-	ExecuteCode(ctx context.Context, code *Code) (string, error) // Executes and returns the output in the string, error in case of server errors not code errors.
+
+	// Executes and returns the output in the string, error in case of server errors not code errors.
+	ExecuteCode(ctx context.Context, code *Code) (string, error)
 
 	// TODO: Is this even needed?
-	GetContainers(ctx context.Context, opts *container.ListOptions) ([]Container, error) // Remove list options if you want some other container type other than docker
+	// Remove list options if you want some other container type other than docker
+	GetContainers(ctx context.Context, opts *container.ListOptions) ([]Container, error)
 }