unit.go

/*
   Copyright 2014 CoreOS, Inc.

   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 unit

import (
	"bytes"
	"crypto/sha1"
	"fmt"
	"io/ioutil"
	"strings"

	"github.com/coreos/fleet/Godeps/_workspace/src/github.com/coreos/go-systemd/unit"
)

func NewUnitFile(raw string) (*UnitFile, error) {
	reader := strings.NewReader(raw)
	opts, err := unit.Deserialize(reader)
	if err != nil {
		return nil, err
	}

	return NewUnitFromOptions(opts), nil
}

func NewUnitFromOptions(opts []*unit.UnitOption) *UnitFile {
	return &UnitFile{mapOptions(opts), opts}
}

func mapOptions(opts []*unit.UnitOption) map[string]map[string][]string {
	contents := make(map[string]map[string][]string)
	for _, opt := range opts {
		if _, ok := contents[opt.Section]; !ok {
			contents[opt.Section] = make(map[string][]string)
		}

		if _, ok := contents[opt.Section][opt.Name]; !ok {
			contents[opt.Section][opt.Name] = make([]string, 0)
		}

		var vals []string
		if opt.Section == "X-Fleet" {
			// The go-systemd parser does not know that our X-Fleet options support
			// multivalue options, so we have to manually parse them here
			vals = parseMultivalueLine(opt.Value)
		} else {
			vals = []string{opt.Value}
		}

		contents[opt.Section][opt.Name] = append(contents[opt.Section][opt.Name], vals...)
	}

	return contents
}

// parseMultivalueLine parses a line that includes several quoted values separated by whitespaces.
// Example: MachineMetadata="foo=bar" "baz=qux"
// If the provided line is not a multivalue string, the line is returned as the sole value.
func parseMultivalueLine(line string) (values []string) {
	if !strings.HasPrefix(line, `"`) || !strings.HasSuffix(line, `"`) {
		return []string{line}
	}

	var v bytes.Buffer
	w := false // check whether we're within quotes or not
	for _, e := range []byte(line) {
		// ignore quotes
		if e == '"' {
			w = !w
			continue
		}

		if e == ' ' {
			if !w { // between quoted values, keep the previous value and reset.
				values = append(values, v.String())
				v.Reset()
				continue
			}
		}

		v.WriteByte(e)
	}

	values = append(values, v.String())

	return
}

// A UnitFile represents a systemd configuration which encodes information about any of the unit
// types that fleet supports (as defined in SupportedUnitTypes()).
// UnitFiles are linked to Units by the Hash of their contents.
// Similar to systemd, a UnitFile configuration has no inherent name, but is rather
// named through the reference to it; in the case of systemd, the reference is
// the filename, and in the case of fleet, the reference is the name of the Unit
// that references this UnitFile.
type UnitFile struct {
	// Contents represents the parsed unit file.
	// This field must be considered readonly.
	Contents map[string]map[string][]string

	Options []*unit.UnitOption
}

// Description returns the first Description option found in the [Unit] section.
// If the option is not defined, an empty string is returned.
func (u *UnitFile) Description() string {
	if values := u.Contents["Unit"]["Description"]; len(values) > 0 {
		return values[0]
	}
	return ""
}

func (u *UnitFile) Bytes() []byte {
	b, _ := ioutil.ReadAll(unit.Serialize(u.Options))
	return b
}

func (u *UnitFile) String() string {
	return string(u.Bytes())
}

// Hash returns the SHA1 hash of the raw contents of the Unit
func (u *UnitFile) Hash() Hash {
	return Hash(sha1.Sum(u.Bytes()))
}

// RecognizedUnitType determines whether or not the given unit name represents
// a recognized unit type.
func RecognizedUnitType(name string) bool {
	types := []string{"service", "socket", "timer", "path", "device", "mount", "automount"}
	for _, t := range types {
		suffix := fmt.Sprintf(".%s", t)
		if strings.HasSuffix(name, suffix) {
			return true
		}
	}
	return false
}

// DefaultUnitType appends the default unit type to a given unit name, ignoring
// any file extensions that already exist.
func DefaultUnitType(name string) string {
	return fmt.Sprintf("%s.service", name)
}

// SHA1 sum
type Hash [sha1.Size]byte

func (h Hash) String() string {
	return fmt.Sprintf("%x", h[:])
}

func (h Hash) Short() string {
	return fmt.Sprintf("%.7s", h)
}

func (h *Hash) Empty() bool {
	return *h == Hash{}
}

// UnitState encodes the current state of a unit loaded into a fleet agent
type UnitState struct {
	LoadState   string
	ActiveState string
	SubState    string
	MachineID   string
	UnitHash    string
	UnitName    string
}

func NewUnitState(loadState, activeState, subState, mID string) *UnitState {
	return &UnitState{
		LoadState:   loadState,
		ActiveState: activeState,
		SubState:    subState,
		MachineID:   mID,
	}
}

// UnitNameInfo exposes certain interesting items about a Unit based on its
// name. For example, a unit with the name "foo@.service" constitutes a
// template unit, and a unit named "foo@1.service" would represent an instance
// unit of that template.
type UnitNameInfo struct {
	FullName string // Original complete name of the unit (e.g. foo.socket, foo@bar.service)
	Name     string // Name of the unit without suffix (e.g. foo, foo@bar)
	Prefix   string // Prefix of the template unit (e.g. foo)

	// If the unit represents an instance or a template, the following values are set
	Template string // Name of the canonical template unit (e.g. foo@.service)
	Instance string // Instance name (e.g. bar)
}

// IsInstance returns a boolean indicating whether the UnitNameInfo appears to be
// an Instance of a Template unit
func (nu UnitNameInfo) IsInstance() bool {
	return len(nu.Instance) > 0
}

// NewUnitNameInfo generates a UnitNameInfo from the given name. If the given string
// is not a correct unit name, nil is returned.
func NewUnitNameInfo(un string) *UnitNameInfo {

	// Everything past the first @ and before the last . is the instance
	s := strings.LastIndex(un, ".")
	if s == -1 {
		return nil
	}

	nu := &UnitNameInfo{FullName: un}
	name := un[:s]
	suffix := un[s:]
	nu.Name = name

	a := strings.Index(name, "@")
	if a == -1 {
		// This does not appear to be a template or instance unit.
		nu.Prefix = name
		return nu
	}

	nu.Prefix = name[:a]
	nu.Template = fmt.Sprintf("%s@%s", name[:a], suffix)
	nu.Instance = name[a+1:]
	return nu
}