kustomize/pkg/plugins/execplugin.go

/*
Copyright 2019 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package plugins

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"syscall"

	"sigs.k8s.io/kustomize/pkg/ifc"
	"sigs.k8s.io/kustomize/pkg/resid"
	"sigs.k8s.io/kustomize/pkg/resmap"
	"sigs.k8s.io/yaml"
)

const (
	ArgsOneLiner = "argsOneLiner"
	ArgsFromFile = "argsFromFile"
)

// ExecPlugin record the name and args of an executable
// It triggers the executable generator and transformer
type ExecPlugin struct {
	// name of the executable
	name string

	// Optional command line arguments to the executable
	// pulled from specially named fields in cfg.
	// This is for executables that don't want to parse YAML.
	args []string

	// Plugin configuration data.
	cfg []byte

	// resmap Factory to make resources
	rf *resmap.Factory

	// loader to load files
	ldr ifc.Loader
}

func NewExecPlugin(root string, id resid.ResId) *ExecPlugin {
	return &ExecPlugin{
		name: filepath.Join(root, pluginPath(id)),
	}
}

// isAvailable checks to see if the plugin is available
func (p *ExecPlugin) isAvailable() bool {
	f, err := os.Stat(p.name)
	if os.IsNotExist(err) {
		return false
	}
	return f.Mode()&0111 != 0000
}

func (p *ExecPlugin) Config(
	ldr ifc.Loader, rf *resmap.Factory, k ifc.Kunstructured) error {
	p.rf = rf
	p.ldr = ldr

	var err error
	p.cfg, err = yaml.Marshal(k)
	if err != nil {
		return err
	}
	err = p.processOptionalArgsFields(k)
	if err != nil {
		return err
	}
	return nil
}

func (p *ExecPlugin) processOptionalArgsFields(k ifc.Kunstructured) error {
	args, err := k.GetFieldValue(ArgsOneLiner)
	if err == nil && args != "" {
		p.args = strings.Split(args, " ")
	}
	fileName, err := k.GetFieldValue(ArgsFromFile)
	if err == nil && fileName != "" {
		content, err := p.ldr.Load(fileName)
		if err != nil {
			return err
		}
		for _, x := range strings.Split(string(content), "\n") {
			x := strings.TrimLeft(x, " ")
			if x != "" {
				p.args = append(p.args, x)
			}
		}
	}
	return nil
}

func (p *ExecPlugin) writeConfig() (string, error) {
	tmpFile, err := ioutil.TempFile("", "kust-pipe")
	if err != nil {
		return "", err
	}
	syscall.Mkfifo(tmpFile.Name(), 0600)
	stdout, err := os.OpenFile(tmpFile.Name(), os.O_RDWR, 0600)
	if err != nil {
		return "", err
	}
	_, err = stdout.Write(p.cfg)
	if err != nil {
		return "", err
	}
	err = stdout.Close()
	if err != nil {
		return "", err
	}
	return tmpFile.Name(), nil
}

func (p *ExecPlugin) Generate() (resmap.ResMap, error) {
	args, err := p.getArgs()
	if err != nil {
		return nil, err
	}
	cmd := exec.Command(p.name, args...)
	cmd.Env = p.getEnv()
	cmd.Stderr = os.Stderr
	if _, err := os.Stat(p.ldr.Root()); err == nil {
		cmd.Dir = p.ldr.Root()
	}
	output, err := cmd.Output()
	if err != nil {
		return nil, err
	}
	return p.rf.NewResMapFromBytes(output)
}

func (p *ExecPlugin) Transform(rm resmap.ResMap) error {
	args, err := p.getArgs()
	if err != nil {
		return err
	}
	for id, r := range rm {
		content, err := yaml.Marshal(r.Kunstructured)
		if err != nil {
			return err
		}
		cmd := exec.Command(p.name, args...)
		cmd.Env = p.getEnv()
		cmd.Stdin = bytes.NewReader(content)
		cmd.Stderr = os.Stderr
		if _, err := os.Stat(p.ldr.Root()); err == nil {
			cmd.Dir = p.ldr.Root()
		}
		output, err := cmd.Output()
		if err != nil {
			return err
		}
		tmpMap, err := p.rf.NewResMapFromBytes(output)
		if err != nil {
			return err
		}
		if len(tmpMap) != 1 {
			return fmt.Errorf("unable to put two resources into one")
		}
		for _, v := range tmpMap {
			rm[id].Kunstructured = v.Kunstructured
		}
	}
	return nil
}

// The first arg is always the absolute path to a temporary file
// holding the YAML form of the plugin config.
func (p *ExecPlugin) getArgs() ([]string, error) {
	configFileName, err := p.writeConfig()
	if err != nil {
		return nil, err
	}
	return append([]string{configFileName}, p.args...), nil
}

func (p *ExecPlugin) getEnv() []string {
	env := os.Environ()
	env = append(env,
		"KUSTOMIZE_PLUGIN_CONFIG_STRING="+string(p.cfg),
		"KUSTOMIZE_PLUGIN_CONFIG_ROOT="+p.ldr.Root())
	return env
}