feat: allow overriding docker executable

So that you can run with DOCKER=nerdctl

Author: afbjorklund

Makefile

@@ -1,5 +1,7 @@
 .PHONY: build
 
+DOCKER = docker
+
 # Development
 
 build_rev := "main"
@@ -35,11 +37,11 @@ run:
 image:
 	@[ -n "$(name)" ] || (echo "Syntax: make image name=<image-name>" >&2; exit 1)
 	@echo "Building image codapi/$(name)"
-	@docker build --file sandboxes/$(name)/Dockerfile --tag codapi/$(name):latest sandboxes/$(name)/
+	@$(DOCKER) build --file sandboxes/$(name)/Dockerfile --tag codapi/$(name):latest sandboxes/$(name)/
 	@echo "✓ codapi/$(name)"
 
 network:
-	docker network create --internal codapi
+	$(DOCKER) network create --internal codapi
 
 # Host OS
 

README.md

@@ -38,7 +38,10 @@ rm -f codapi.tar.gz
 3. Build the sample `ash` sandbox image:
 
 ```sh
-docker build --file sandboxes/ash/Dockerfile --tag codapi/ash:latest sandboxes/ash
+# optional: $DOCKER
+export DOCKER=docker
+
+$DOCKER build --file sandboxes/ash/Dockerfile --tag codapi/ash:latest sandboxes/ash
 ```
 
 4. Start the server:

codapi-cli

@@ -2,6 +2,7 @@
 set -euo pipefail
 
 cd "$(dirname "$0")"
+docker=${DOCKER:-docker}
 sandboxes_dir="sandboxes"
 codapi_url="${CODAPI_URL:-localhost:1313}"
 
@@ -225,9 +226,9 @@ do_sandbox_rm() {
     fi
 
     # 1. Remove the container if it exists.
-    if docker ps -a -q --filter "name=$name" | grep -q .; then
+    if $docker ps -a -q --filter "name=$name" | grep -q .; then
         echo "Removing container '$name'..."
-        docker rm -f "$name"
+        $docker rm -f "$name"
     fi
 
     # 2. Remove the directory and its contents.

internal/engine/docker.go

@@ -31,12 +31,18 @@ const (
 type Docker struct {
 	cfg *config.Config
 	cmd *config.Command
+	exe string // docker
 }
 
 // NewDocker creates a new Docker engine for a specific command.
 func NewDocker(cfg *config.Config, sandbox, command string) Engine {
 	cmd := cfg.Commands[sandbox][command]
-	return &Docker{cfg, cmd}
+	exe := "docker"
+	// override docker with similar command
+	if env, ok := os.LookupEnv("DOCKER"); ok {
+		exe = env
+	}
+	return &Docker{cfg, cmd, exe}
 }
 
 // Exec executes the command and returns the output.
@@ -196,10 +202,10 @@ func (e *Docker) exec(box *config.Box, step *config.Step, req Request, dir strin
 	if step.Stdin {
 		// pass files to container from stdin
 		stdin := filesReader(files)
-		stdout, stderr, err = prog.RunStdin(stdin, req.ID, "docker", args...)
+		stdout, stderr, err = prog.RunStdin(stdin, req.ID, e.exe, args...)
 	} else {
 		// pass files to container from temp directory
-		stdout, stderr, err = prog.Run(req.ID, "docker", args...)
+		stdout, stderr, err = prog.Run(req.ID, e.exe, args...)
 	}
 
 	if err == nil {
@@ -213,7 +219,7 @@ func (e *Docker) exec(box *config.Box, step *config.Step, req Request, dir strin
 			// inside the container is not related to the "docker run" process,
 			// and will hang forever after the "docker run" process is killed
 			go func() {
-				err = dockerKill(req.ID)
+				err = dockerKill(e.exe, req.ID)
 				if err == nil {
 					logx.Debug("%s: docker kill ok", req.ID)
 				} else {
@@ -259,7 +265,7 @@ func (e *Docker) buildArgs(box *config.Box, step *config.Step, req Request, dir
 
 	command := expandVars(step.Command, req.ID)
 	args = append(args, command...)
-	logx.Debug("%v", args)
+	logx.Debug("%s %v", e.exe, args)
 	return args
 }
 
@@ -345,9 +351,9 @@ func expandVars(command []string, name string) []string {
 }
 
 // dockerKill kills the container with the specified id/name.
-func dockerKill(id string) error {
+func dockerKill(exe, id string) error {
 	ctx, cancel := context.WithTimeout(context.Background(), killTimeout)
 	defer cancel()
-	cmd := exec.CommandContext(ctx, "docker", "kill", id)
+	cmd := exec.CommandContext(ctx, exe, "kill", id)
 	return execy.Run(cmd)
 }

internal/engine/docker_test.go

@@ -139,6 +139,7 @@ var dockerCfg = &config.Config{
 
 func TestDockerRun(t *testing.T) {
 	logx.Mock()
+	t.Setenv("DOCKER", "docker")
 	commands := map[string]execy.CmdOut{
 		"docker run": {Stdout: "hello world", Stderr: "", Err: nil},
 	}
@@ -257,6 +258,7 @@ func TestDockerRun(t *testing.T) {
 
 func TestDockerExec(t *testing.T) {
 	logx.Mock()
+	t.Setenv("DOCKER", "docker")
 	commands := map[string]execy.CmdOut{
 		"docker exec": {Stdout: "hello world", Stderr: "", Err: nil},
 	}
@@ -287,6 +289,7 @@ func TestDockerExec(t *testing.T) {
 
 func TestDockerStop(t *testing.T) {
 	logx.Mock()
+	t.Setenv("DOCKER", "docker")
 	commands := map[string]execy.CmdOut{
 		"docker run":  {Stdout: "c958ff2", Stderr: "", Err: nil},
 		"docker exec": {Stdout: "hello", Stderr: "", Err: nil},

internal/sandbox/sandbox_test.go

@@ -1,6 +1,7 @@
 package sandbox
 
 import (
+	"os"
 	"testing"
 
 	"github.com/nalgeon/be"
@@ -56,9 +57,13 @@ func TestValidate(t *testing.T) {
 
 func TestExec(t *testing.T) {
 	_ = ApplyConfig(cfg)
+	docker := os.Getenv("DOCKER")
+	if docker == "" {
+		docker = "docker"
+	}
 	t.Run("exec", func(t *testing.T) {
 		execy.Mock(map[string]execy.CmdOut{
-			"docker run": {Stdout: "hello"},
+			docker + " run": {Stdout: "hello"},
 		})
 		req := engine.Request{
 			ID:      "http_42",

internal/server/router_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 
 	"github.com/nalgeon/be"
@@ -57,8 +58,12 @@ func (s *server) close() {
 
 func Test_exec(t *testing.T) {
 	_ = sandbox.ApplyConfig(cfg)
+	docker := os.Getenv("DOCKER")
+	if docker == "" {
+		docker = "docker"
+	}
 	execy.Mock(map[string]execy.CmdOut{
-		"docker run": {Stdout: "hello"},
+		docker + " run": {Stdout: "hello"},
 	})
 
 	srv := newServer()