Allow entrypoint binary to wait for multiple files

cmd/entrypoint/main.go

@@ -21,6 +21,7 @@ import (
 	"log"
 	"os"
 	"os/exec"
+	"strings"
 	"syscall"
 	"time"
 
@@ -29,7 +30,7 @@ import (
 
 var (
 	ep              = flag.String("entrypoint", "", "Original specified entrypoint to execute")
-	waitFile        = flag.String("wait_file", "", "If specified, file to wait for")
+	waitFiles       = flag.String("wait_file", "", "Comma-separated list of paths to wait for")
 	waitFileContent = flag.Bool("wait_file_content", false, "If specified, expect wait_file to have content")
 	postFile        = flag.String("post_file", "", "If specified, file to write upon completion")
 
@@ -41,7 +42,7 @@ func main() {
 
 	e := entrypoint.Entrypointer{
 		Entrypoint:      *ep,
-		WaitFile:        *waitFile,
+		WaitFiles:       strings.Split(*waitFiles, ","),
 		WaitFileContent: *waitFileContent,
 		PostFile:        *postFile,
 		Args:            flag.Args(),

pkg/entrypoint/entrypointer.go

@@ -27,9 +27,9 @@ type Entrypointer struct {
 	Entrypoint string
 	// Args are the original specified args, if any.
 	Args []string
-	// WaitFile is the file to wait for. If not specified, execution begins
-	// immediately.
-	WaitFile string
+	// WaitFiles is the set of files to wait for. If empty, execution
+	// begins immediately.
+	WaitFiles []string
 	// WaitFileContent indicates the WaitFile should have non-zero size
 	// before continuing with execution.
 	WaitFileContent bool
@@ -65,10 +65,10 @@ type PostWriter interface {
 // Go optionally waits for a file, runs the command, and writes a
 // post file.
 func (e Entrypointer) Go() error {
-	if e.WaitFile != "" {
-		if err := e.Waiter.Wait(e.WaitFile, e.WaitFileContent); err != nil {
+	for _, f := range e.WaitFiles {
+		if err := e.Waiter.Wait(f, e.WaitFileContent); err != nil {
 			// An error happened while waiting, so we bail
-			// *but* we write postfile to make next steps bail too
+			// *but* we write postfile to make next steps bail too.
 			e.WritePostFile(e.PostFile, err)
 			return err
 		}

pkg/entrypoint/entrypointer_test.go

@@ -26,10 +26,11 @@ import (
 
 func TestEntrypointerFailures(t *testing.T) {
 	for _, c := range []struct {
-		desc, waitFile, postFile string
-		waiter                   Waiter
-		runner                   Runner
-		expectedError            string
+		desc, postFile string
+		waitFiles      []string
+		waiter         Waiter
+		runner         Runner
+		expectedError  string
 	}{{
 		desc:          "failing runner with no postFile",
 		runner:        &fakeErrorRunner{},
@@ -41,12 +42,12 @@ func TestEntrypointerFailures(t *testing.T) {
 		postFile:      "foo",
 	}, {
 		desc:          "failing waiter with no postFile",
-		waitFile:      "foo",
+		waitFiles:     []string{"foo"},
 		waiter:        &fakeErrorWaiter{},
 		expectedError: "waiter failed",
 	}, {
 		desc:          "failing waiter with postFile",
-		waitFile:      "foo",
+		waitFiles:     []string{"foo"},
 		waiter:        &fakeErrorWaiter{},
 		expectedError: "waiter failed",
 		postFile:      "bar",
@@ -63,7 +64,7 @@ func TestEntrypointerFailures(t *testing.T) {
 			fpw := &fakePostWriter{}
 			err := Entrypointer{
 				Entrypoint: "echo",
-				WaitFile:   c.waitFile,
+				WaitFiles:  c.waitFiles,
 				PostFile:   c.postFile,
 				Args:       []string{"some", "args"},
 				Waiter:     fw,
@@ -93,8 +94,8 @@ func TestEntrypointerFailures(t *testing.T) {
 
 func TestEntrypointer(t *testing.T) {
 	for _, c := range []struct {
-		desc, entrypoint, waitFile, postFile string
-		args                                 []string
+		desc, entrypoint, postFile string
+		waitFiles, args            []string
 	}{{
 		desc: "do nothing",
 	}, {
@@ -107,22 +108,25 @@ func TestEntrypointer(t *testing.T) {
 		desc: "just args",
 		args: []string{"just", "args"},
 	}, {
-		desc:     "wait file",
-		waitFile: "waitforme",
+		desc:      "wait file",
+		waitFiles: []string{"waitforme"},
 	}, {
 		desc:     "post file",
 		postFile: "writeme",
 	}, {
 		desc:       "all together now",
 		entrypoint: "echo", args: []string{"some", "args"},
-		waitFile: "waitforme",
-		postFile: "writeme",
+		waitFiles: []string{"waitforme"},
+		postFile:  "writeme",
+	}, {
+		desc:      "multiple wait files",
+		waitFiles: []string{"waitforme", "metoo", "methree"},
 	}} {
 		t.Run(c.desc, func(t *testing.T) {
 			fw, fr, fpw := &fakeWaiter{}, &fakeRunner{}, &fakePostWriter{}
 			err := Entrypointer{
 				Entrypoint: c.entrypoint,
-				WaitFile:   c.waitFile,
+				WaitFiles:  c.waitFiles,
 				PostFile:   c.postFile,
 				Args:       c.args,
 				Waiter:     fw,
@@ -133,14 +137,14 @@ func TestEntrypointer(t *testing.T) {
 				t.Fatalf("Entrypointer failed: %v", err)
 			}
 
-			if c.waitFile != "" {
+			if len(c.waitFiles) > 0 {
 				if fw.waited == nil {
 					t.Error("Wanted waited file, got nil")
-				} else if *fw.waited != c.waitFile {
-					t.Errorf("Waited for %q, want %q", *fw.waited, c.waitFile)
+				} else if !reflect.DeepEqual(fw.waited, c.waitFiles) {
+					t.Errorf("Waited for %v, want %v", fw.waited, c.waitFiles)
 				}
 			}
-			if c.waitFile == "" && fw.waited != nil {
+			if len(c.waitFiles) == 0 && fw.waited != nil {
 				t.Errorf("Waited for file when not required")
 			}
 
@@ -173,10 +177,10 @@ func TestEntrypointer(t *testing.T) {
 	}
 }
 
-type fakeWaiter struct{ waited *string }
+type fakeWaiter struct{ waited []string }
 
-func (f *fakeWaiter) Wait(file string, expectContent bool) error {
-	f.waited = &file
+func (f *fakeWaiter) Wait(file string, _ bool) error {
+	f.waited = append(f.waited, file)
 	return nil
 }