Beam's Python SDK harness boot entrypoint may fail when python is not…

… accessible, but python3 is. apache#26958 fixed

sdks/python/container/boot.go

@@ -91,7 +91,7 @@ func main() {
 			"--container_executable=/opt/apache/beam/boot",
 		}
 		log.Printf("Starting worker pool %v: python %v", workerPoolId, strings.Join(args, " "))
-		if err := execx.Execute("python", args...); err != nil {
+		if err := execx.Execute("python3", args...); err != nil {
 			log.Fatalf("Python SDK worker pool exited with error: %v", err)
 		}
 		log.Print("Python SDK worker pool exited.")
@@ -330,7 +330,7 @@ func setupVenv(ctx context.Context, logger *tools.Logger, baseDir, workerId stri
 	if err := os.MkdirAll(dir, 0750); err != nil {
 		return "", fmt.Errorf("failed to create Python venv directory: %s", err)
 	}
-	if err := execx.Execute("python", "-m", "venv", "--system-site-packages", dir); err != nil {
+	if err := execx.Execute("python3", "-m", "venv", "--system-site-packages", dir); err != nil {
 		return "", fmt.Errorf("python venv initialization failed: %s", err)
 	}
 

sdks/python/container/piputil.go

@@ -38,14 +38,14 @@ func pipInstallRequirements(files []string, dir, name string) error {
 			// option will make sure that only things staged in the worker will be
 			// used without following their dependencies.
 			args := []string{"-m", "pip", "install", "-r", filepath.Join(dir, name), "--no-cache-dir", "--disable-pip-version-check", "--no-index", "--no-deps", "--find-links", dir}
-			if err := execx.Execute("python", args...); err != nil {
+			if err := execx.Execute("python3", args...); err != nil {
 				fmt.Println("Some packages could not be installed solely from the requirements cache. Installing packages from PyPI.")
 			}
 			// The second install round opens up the search for packages on PyPI and
 			// also installs dependencies. The key is that if all the packages have
 			// been installed in the first round then this command will be a no-op.
 			args = []string{"-m", "pip", "install", "-r", filepath.Join(dir, name), "--no-cache-dir", "--disable-pip-version-check", "--find-links", dir}
-			return execx.Execute("python", args...)
+			return execx.Execute("python3", args...)
 		}
 	}
 	return nil
@@ -78,17 +78,17 @@ func pipInstallPackage(files []string, dir, name string, force, optional bool, e
 				// installed if necessary.  This achieves our goal outlined above.
 				args := []string{"-m", "pip", "install", "--no-cache-dir", "--disable-pip-version-check", "--upgrade", "--force-reinstall", "--no-deps",
 					filepath.Join(dir, packageSpec)}
-				err := execx.Execute("python", args...)
+				err := execx.Execute("python3", args...)
 				if err != nil {
 					return err
 				}
 				args = []string{"-m", "pip", "install", "--no-cache-dir", "--disable-pip-version-check", filepath.Join(dir, packageSpec)}
-				return execx.Execute("python", args...)
+				return execx.Execute("python3", args...)
 			}
 
 			// Case when we do not perform a forced reinstall.
 			args := []string{"-m", "pip", "install", "--no-cache-dir", "--disable-pip-version-check", filepath.Join(dir, packageSpec)}
-			return execx.Execute("python", args...)
+			return execx.Execute("python3", args...)
 		}
 	}
 	if optional {

sdks/python/expansion-service-container/boot.go

@@ -65,7 +65,7 @@ func launchExpansionServiceProcess() error {
 	os.Setenv("PATH", strings.Join([]string{filepath.Join(dir, "bin"), os.Getenv("PATH")}, ":"))
 
 	args := []string{"-m", expansionServiceEntrypoint, "-p", strconv.Itoa(*port), "--fully_qualified_name_glob", "*"}
-	if err := execx.Execute("python", args...); err != nil {
+	if err := execx.Execute("python3", args...); err != nil {
 		return fmt.Errorf("Could not start the expansion service: %s", err)
 	}