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evaluator.go
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evaluator.go
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// Package evaluator is the core of our run-time.
//
// Given a parsed series of statements we execute each of them in turn.
package evaluator
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"path"
"path/filepath"
"regexp"
"strings"
"syscall"
"text/template"
"time"
"github.com/sfreiberg/simplessh"
"github.com/skx/deployr/statement"
"github.com/skx/deployr/util"
"golang.org/x/crypto/ssh/terminal"
)
// Evaluator holds our internal state.
type Evaluator struct {
// Program is our parsed program, which is an array of statements.
Program []statement.Statement
// Identity holds the SSH key to authenticate with
Identity string
// Verbose is true if the execution should be verbose.
Verbose bool
// NOP records if we should pretend to work, or work for real.
NOP bool
// Variables is a map which holds the names/values of all defined
// variables. (Being declared/set/updated via the 'Set' primitive.)
Variables map[string]string
// ROVariables is a map which is similar to Variables, but only
// contains values set on the command-line. Variables are looked
// for here first.
ROVariables map[string]string
// Connection holds the SSH-connection to the remote-host.
Connection *simplessh.Client
// Changed records whether the last copy operaton resulted in a change.
Changed bool
}
// New creates our evaluator object, which will execute the supplied
// statements.
func New(program []statement.Statement) *Evaluator {
p := &Evaluator{Program: program}
// Setup the maps for storing variable names & values.
p.Variables = make(map[string]string)
p.ROVariables = make(map[string]string)
return p
}
// SetIdentity specifies the SSH identity file to authenticate with
func (e *Evaluator) SetIdentity(file string) {
if file != "" {
e.Identity = file
} else {
e.Identity = os.Getenv("HOME") + "/.ssh/id_rsa"
}
}
// SetNOP specifies whether we should run for real, or not at all.
func (e *Evaluator) SetNOP(verb bool) {
e.NOP = verb
}
// SetVerbose specifies whether we should run verbosely or not.
func (e *Evaluator) SetVerbose(verb bool) {
e.Verbose = verb
}
// ConnectTo opens the SSH connection to the specified target-host.
//
// If a connection is already open then it is maintained, and not replaced.
// This allows the command-line to override the destination which might be
// baked into a configuration-recipe.
//
func (e *Evaluator) ConnectTo(target string) error {
var err error
if e.Connection != nil {
fmt.Printf("Ignoring request to change target mid-run!\n")
return nil
}
//
// Default username + port
//
user := "root"
port := "22"
host := ""
//
// Setup the user if we have it
//
if strings.Contains(target, "@") {
fields := strings.Split(target, "@")
user = fields[0]
host = fields[1]
} else {
host = target
}
//
// Setup the port if we have it
//
if strings.Contains(host, ":") {
fields := strings.Split(host, ":")
host = fields[0]
port = fields[1]
}
//
// Store our connection-details in the variable-list
//
e.Variables["host"] = host
e.Variables["port"] = port
e.Variables["user"] = user
//
// Setup our destination with the host/port
//
destination := fmt.Sprintf("%s:%s", host, port)
//
// Finally connect.
//
if util.HasSSHAgent() {
e.Connection, err = simplessh.ConnectWithAgent(destination, user)
} else {
e.Connection, err = simplessh.ConnectWithKeyFile(destination, user, e.Identity)
}
if err != nil {
return err
}
return nil
}
// Run evaluates our program, continuing until all statements have been
// executed - unless an error was encountered.
func (e *Evaluator) Run() error {
//
// Do any of our program-statements require the use of Sudo?
//
sudo := false
for _, statement := range e.Program {
if statement.Sudo {
sudo = true
}
}
//
// OK we need a sudo-password. So prompt for it.
//
sudoPassword := ""
if sudo {
fmt.Printf("Please enter your password for sudo: ")
text, err := terminal.ReadPassword(int(syscall.Stdin))
if err != nil {
return err
}
fmt.Printf("\n")
sudoPassword = string(text)
}
//
// For each statement ..
//
for _, statement := range e.Program {
//
// The action to be taken will depend upon the type
// of the token.
//
switch statement.Token.Type {
case "CopyTemplate":
//
// Ensure we're connected.
//
if e.Connection == nil {
return fmt.Errorf("tried to run a command, but not connected to a target")
}
//
// Get the arguments and run the copy.
//
src := e.expandString(statement.Arguments[0].Literal)
dst := e.expandString(statement.Arguments[1].Literal)
if e.Verbose {
fmt.Printf("CopyTemplate(\"%s\", \"%s\")\n", src, dst)
}
if e.NOP {
break
}
e.Changed = e.copyFiles(src, dst, true)
case "CopyFile":
//
// Ensure we're connected.
//
if e.Connection == nil {
return fmt.Errorf("tried to run a command, but not connected to a target")
}
//
// Get the arguments and run the copy.
//
src := e.expandString(statement.Arguments[0].Literal)
dst := e.expandString(statement.Arguments[1].Literal)
if e.Verbose {
fmt.Printf("CopyFile(\"%s\", \"%s\")\n", src, dst)
}
if e.NOP {
break
}
e.Changed = e.copyFiles(src, dst, false)
case "DeployTo":
//
// Get the arguments, and connect.
//
arg := e.expandString(statement.Arguments[0].Literal)
if e.Verbose {
fmt.Printf("DeployTo(\"%s\")\n", arg)
}
err := e.ConnectTo(arg)
if err != nil {
return err
}
case "IfChanged":
//
// If the previous copy didn't change then we can
// just skip this command.
//
if !e.Changed {
break
}
//
// Ensure we're connected.
//
if e.Connection == nil {
return fmt.Errorf("tried to run a command, but not connected to a target")
}
//
// Get the command to execute.
//
cmd := e.expandString(statement.Arguments[0].Literal)
if e.Verbose {
if statement.Sudo {
fmt.Printf("Sudo ")
}
fmt.Printf("IfChanged(\"%s\")\n", cmd)
}
if e.NOP {
break
}
//
// Holder for results of execution.
//
var result []byte
var err error
//
// Run via sudo or normally.
//
if statement.Sudo {
result, err = e.Connection.ExecSudo(cmd, sudoPassword)
} else {
result, err = e.Connection.Exec(cmd)
}
if err != nil {
return (fmt.Errorf("failed to run command '%s': %s\n%s", cmd, err.Error(), result))
}
//
// Show the output
//
fmt.Printf("%s", result)
case "Run":
//
// Ensure we're connected.
//
if e.Connection == nil {
return fmt.Errorf("tried to run a command, but not connected to a target")
}
cmd := e.expandString(statement.Arguments[0].Literal)
if e.Verbose {
if statement.Sudo {
fmt.Printf("Sudo ")
}
fmt.Printf("Run(\"%s\")\n", cmd)
}
if e.NOP {
break
}
//
// Holder for results of execution.
//
var result []byte
var err error
//
// Run via sudo or normally.
//
if statement.Sudo {
result, err = e.Connection.ExecSudo(cmd, sudoPassword)
} else {
result, err = e.Connection.Exec(cmd)
}
if err != nil {
return (fmt.Errorf("failed to run command '%s': %s\n%s", cmd, err.Error(), result))
}
//
// Show the output
//
fmt.Printf("%s", result)
case "Set":
//
// Get the arguments and set the variable.
//
key := statement.Arguments[0].Literal
val := e.expandString(statement.Arguments[1].Literal)
if e.Verbose {
fmt.Printf("Set(\"%s\", \"%s\")\n", key, val)
}
e.Variables[key] = val
case "Sudo":
//
// This is an error?
//
default:
return fmt.Errorf("unhandled statement - %v", statement.Token)
}
}
//
// Disconnect from the remote host, if we connected.
//
if e.Connection != nil {
if e.Verbose {
fmt.Printf("Disconnecting from remote-host\n")
}
e.Connection.Close()
}
//
// All done.
//
return nil
}
// copyFiles is designed to copy a file/template from the local
// system to the remote host.
//
// It might be called with a glob, or with a single file.
//
func (e *Evaluator) copyFiles(pattern string, destination string, expand bool) bool {
//
// If our input pattern ends with a "/" we just add "*"
//
if strings.HasSuffix(pattern, "/") {
pattern += "*"
}
//
// Expand the pattern we received.
//
files, err := filepath.Glob(pattern)
if err != nil {
return false
}
//
// Did we fail to find file(s)?
//
if len(files) < 1 {
fmt.Printf("Failed to find file(s) matching %s\n", pattern)
return false
}
//
// Did we receive more than one file?
//
if len(files) == 1 && files[0] == pattern {
//
// OK just copying a single file.
//
return (e.copyFile(pattern, destination, expand))
}
//
// OK we now have to copy each entry. Since we're copying
// from a pattern our destination will need to be updated ensure
// we have a trailing "/" for that.
//
if !strings.HasSuffix(destination, "/") {
destination += "/"
}
//
// We record a change if we updated ANY of the files.
//
changed := false
//
// Now process each file.
//
for _, file := range files {
fi, err := os.Stat(file)
if err != nil {
fmt.Printf("Failed to stat(%s) %s\n", file, err.Error())
continue
}
switch mode := fi.Mode(); {
case mode.IsDir():
if e.Verbose {
fmt.Printf("Skipping directory %s\n", file)
}
case mode.IsRegular():
name := path.Base(file)
c := e.copyFile(file, destination+name, expand)
if c {
changed = c
}
}
}
//
return changed
}
// copyFile is designed to copy the local file to the remote system.
//
// It is a little complex because it does two extra things:
//
// * It only copies files if the local/remote differ.
//
// * It optionally expands template-variables.
//
func (e *Evaluator) copyFile(local string, remote string, expand bool) bool {
//
// Did we result in a change?
//
changed := false
if e.Verbose {
if expand {
fmt.Printf("CopyTemplate(\"%s\",\"%s\")\n", local, remote)
} else {
fmt.Printf("CopyFile(\"%s\",\"%s\")\n", local, remote)
}
}
//
// If we're expanding templates then do that first of all.
//
// * Load the source file.
//
// * Perform the template-expansion of variables.
//
// * Write that expanded result to a temporary file.
//
// * Swap out the local-file name with the temporary-file.
//
if expand {
//
// Read the input file.
//
data, err := ioutil.ReadFile(local)
//
// If we can't read the input-file that's a fatal error.
//
if err != nil {
fmt.Printf("Failed to read local file to expand template-variables %s\n", err.Error())
os.Exit(11)
}
//
// Define a helper-function that users can call to get
// the variables they've set.
//
funcMap := template.FuncMap{
"get": func(s string) string {
if len(e.ROVariables[s]) > 0 {
return (e.ROVariables[s])
}
return (e.Variables[s])
},
"now": time.Now,
}
//
// Load the file as a template.
//
tmpl := template.Must(template.New("tmpl").Funcs(funcMap).Parse(string(data)))
//
// Now expand the template into a temporary-buffer.
//
buf := &bytes.Buffer{}
tmpl.Execute(buf, e.Variables)
//
// Finally write that to a temporary file, and ensure
// that is the source of the copy.
//
tmpfile, _ := ioutil.TempFile("", "tmpl")
local = tmpfile.Name()
ioutil.WriteFile(local, buf.Bytes(), 0600)
}
//
// Copying a file to the remote host is
// very simple - BUT we want to know if the
// remote file changed, so we can make a
// conditional result sometimes.
//
// So we need to hash the local file, and
// the remote (if it exists) and compare
// the two.
//
//
// NOTE: We do this after we've expanded any variables.
//
var hashLocal string
var err error
hashLocal, err = util.HashFile(local)
if err != nil {
fmt.Printf("Failed to hash local file %s\n", err.Error())
//
// If we're trying to copy a file that doesn't exist that
// is a fatal error.
//
os.Exit(11)
}
//
// Now fetch the file from the remote host, if we can.
//
tmpfile, _ := ioutil.TempFile("", "example")
defer os.Remove(tmpfile.Name()) // clean up
err = e.Connection.Download(remote, tmpfile.Name())
if err == nil {
//
// We had no error - so we now have the
// remote file copied here.
//
var hashRemote string
hashRemote, err = util.HashFile(tmpfile.Name())
if err != nil {
fmt.Printf("Failed to hash remote file %s\n", err.Error())
// If expanding variables we replaced our
// input-file with the temporary result of
// expansion.
if expand {
os.Remove(local)
}
return changed
}
if hashRemote != hashLocal {
if e.Verbose {
fmt.Printf("\tFile on remote host needs replacing.\n")
}
changed = true
} else {
if e.Verbose {
fmt.Printf("\tFile on remote host doesn't need to be changed.\n")
}
}
} else {
//
// If we failed to find the file we
// assume thati t doesn't exist
//
if strings.Contains(err.Error(), "not exist") {
changed = true
}
}
//
// Upload the file, if it changed
//
if changed {
err = e.Connection.Upload(local, remote)
if err != nil {
fmt.Printf("Failed to upload '%s' to '%s': %s\n", local, remote, err.Error())
// If expanding variables we replaced our
// input-file with the temporary result of
// expansion.
if expand {
os.Remove(local)
}
return changed
}
}
// If expanding variables we replaced our
// input-file with the temporary result of
// expansion.
if expand {
os.Remove(local)
}
return changed
}
// expandString expands tokens of the form "${blah}" into the
// value of the variable "blah".
func (e *Evaluator) expandString(in string) string {
//
// Expand any variables which have previously been
// declared.
//
re := regexp.MustCompile(`\$\{([^\}]+)\}`)
in = re.ReplaceAllStringFunc(in, func(in string) string {
in = strings.TrimPrefix(in, "${")
in = strings.TrimSuffix(in, "}")
// Look for read-only variables first
if len(e.ROVariables[in]) > 0 {
return (e.ROVariables[in])
}
// Now look for normal-variable
if len(e.Variables[in]) > 0 {
return (e.Variables[in])
}
// Finally we found neither, just leave the
// expansion alone.
return "${" + in + "}"
})
return in
}
// SetVariable sets the content of a read-only variable
func (e *Evaluator) SetVariable(key string, val string) {
e.ROVariables[key] = val
}