First cut to spawner

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

internal/server/user/spawn.go

@@ -0,0 +1,22 @@
+package user
+
+import (
+	"io"
+	"os"
+	"os/exec"
+
+	"github.com/BBVA/kapow/internal/server/model"
+)
+
+func spawn(h *model.Handler, out io.Writer) error {
+	cmd := exec.Command(h.Route.Entrypoint)
+	if out != nil {
+		cmd.Stdout = out
+	}
+	cmd.Env = append(os.Environ(), "KAPOW_URL=http://localhost:8081")
+	cmd.Env = append(cmd.Env, "KAPOW_HANDLER_ID="+h.ID)
+
+	err := cmd.Run()
+
+	return err
+}

internal/server/user/spawn_test.go

@@ -0,0 +1,125 @@
+package user
+
+import (
+	"bytes"
+	"encoding/json"
+	"log"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"github.com/BBVA/kapow/internal/server/model"
+)
+
+type Output struct {
+	Cmdline []string          `json:"cmdline"`
+	Env     map[string]string `json:"env"`
+}
+
+func decodeJailLover(out []byte) (jldata Output) {
+	err := json.Unmarshal(out, &jldata)
+	if err != nil {
+		log.Fatal("jaillover output is malformed", err)
+	}
+	return
+}
+
+func locateJailLover() string {
+	out, err := exec.Command("which", "jaillover").Output()
+	if err != nil {
+		log.Fatal("jaillover not found in PATH", err)
+	}
+	return strings.TrimRight(string(out), "\n")
+}
+
+func TestSpawnRetursErrorWhenEntrypointIsBad(t *testing.T) {
+	r := &model.Route{
+		Entrypoint: "/bin/this_executable_is_not_likely_to_exist",
+	}
+
+	h := &model.Handler{
+		Route: r,
+	}
+
+	err := spawn(h, nil)
+	if err == nil {
+		t.Error("Bad executable not reported")
+	}
+}
+
+func TestSpawnReturnsNilWhenEntrypointIsGood(t *testing.T) {
+	r := &model.Route{
+		Entrypoint: locateJailLover(),
+	}
+
+	h := &model.Handler{
+		Route: r,
+	}
+
+	err := spawn(h, nil)
+	if err != nil {
+		t.Error("Good executable reported")
+	}
+}
+
+func TestSpawnWritesToStdout(t *testing.T) {
+	r := &model.Route{
+		Entrypoint: locateJailLover(),
+	}
+
+	h := &model.Handler{
+		Route: r,
+	}
+
+	out := &bytes.Buffer{}
+
+	_ = spawn(h, out)
+
+	jldata := decodeJailLover(out.Bytes())
+
+	if jldata.Cmdline[0] != locateJailLover() {
+		t.Error("Ouput does not match jaillover's")
+	}
+
+}
+
+func TestSpawnSetsKapowURLEnvVar(t *testing.T) {
+	r := &model.Route{
+		Entrypoint: locateJailLover(),
+	}
+
+	h := &model.Handler{
+		Route: r,
+	}
+
+	out := &bytes.Buffer{}
+
+	_ = spawn(h, out)
+
+	jldata := decodeJailLover(out.Bytes())
+
+	if v, ok := jldata.Env["KAPOW_URL"]; !ok || v != "http://localhost:8081" {
+		t.Error("KAPOW_URL is not set properly")
+	}
+}
+
+func TestSpawnSetsKapowHandlerIDEnvVar(t *testing.T) {
+	r := &model.Route{
+		Entrypoint: locateJailLover(),
+	}
+
+	h := &model.Handler{
+		ID:    "HANDLER_ID_FOO",
+		Route: r,
+	}
+
+	out := &bytes.Buffer{}
+
+	_ = spawn(h, out)
+
+	jldata := decodeJailLover(out.Bytes())
+
+	if v, ok := jldata.Env["KAPOW_HANDLER_ID"]; !ok || v != "HANDLER_ID_FOO" {
+		t.Error("KAPOW_HANDLER_ID is not set properly")
+	}
+}