Use a lockfile to serialize blessclient invocations (#84)

Use a lockfile to serialize blessclient invocationsWhen integrated with tools like terraform or ansible, multiple concurrent runs of blessclient resulted in unnecessary work. Instead, serialize blessclient commands.

Gopkg.toml

@@ -1,11 +1,15 @@
 [[constraint]]
   name = "github.com/aws/aws-sdk-go"
-  version = "1.15.76"
+  version = "1.15.79"
 
 [[constraint]]
   name = "github.com/blang/semver"
   version = "3.5.1"
 
+[[constraint]]
+  name = "github.com/cenkalti/backoff"
+  version = "2.0.0"
+
 [[constraint]]
   branch = "master"
   name = "github.com/chanzuckerberg/go-misc"
@@ -16,7 +20,7 @@
 
 [[constraint]]
   name = "github.com/google/uuid"
-  version = "1.0.0"
+  version = "1.1.0"
 
 [[constraint]]
   branch = "master"
@@ -34,6 +38,10 @@
   name = "github.com/mitchellh/go-homedir"
   version = "1.0.0"
 
+[[constraint]]
+  branch = "master"
+  name = "github.com/nightlyone/lockfile"
+
 [[constraint]]
   name = "github.com/pkg/errors"
   version = "0.8.0"

cmd/import-config.go

@@ -24,11 +24,9 @@ import (
 
 const (
 	flagKeyFile = "key-file"
-	flagConfig  = "config"
 )
 
 func init() {
-	importConfigCmd.Flags().StringP(flagConfig, "c", config.DefaultConfigFile, "Use this to override the bless config file.")
 	importConfigCmd.Flags().StringP(flagKeyFile, "k", config.DefaultSSHPrivateKey, "Location of SSH private key")
 	rootCmd.AddCommand(importConfigCmd)
 }

cmd/root.go

@@ -1,33 +1,53 @@
 package cmd
 
 import (
+	"github.com/chanzuckerberg/blessclient/pkg/config"
+	"github.com/chanzuckerberg/blessclient/pkg/util"
 	"github.com/pkg/errors"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
 
+const (
+	flagConfig  = "config"
+	flagVerbose = "verbose"
+)
+
 func init() {
-	rootCmd.PersistentFlags().BoolP("verbose", "v", false, "Use this to enable verbose mode")
+	rootCmd.PersistentFlags().StringP(flagConfig, "c", config.DefaultConfigFile, "Use this to override the bless config file.")
+	rootCmd.PersistentFlags().BoolP(flagVerbose, "v", false, "Use this to enable verbose mode")
 }
 
+var pidLock *util.Lock
 var rootCmd = &cobra.Command{
 	Use:   "blessclient",
 	Short: "",
+	PersistentPostRunE: func(cmd *cobra.Command, args []string) error {
+		return errors.Wrap(pidLock.Unlock(), "Error releasing lock")
+	},
 	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
-		verbose, err := cmd.Flags().GetBool("verbose")
+		verbose, err := cmd.Flags().GetBool(flagVerbose)
 		if err != nil {
 			return errors.Wrap(err, "Missing verbose flag")
 		}
 		if verbose {
 			log.SetLevel(log.DebugLevel)
 		}
-		return nil
+
+		// pid lock
+		configPath, err := util.GetConfigPath(cmd)
+		if err != nil {
+			return err
+		}
+		pidLock, err = util.NewLock(configPath)
+		if err != nil {
+			return err
+		}
+		return errors.Wrap(pidLock.Lock(), "Error acquiring lock")
 	},
 }
 
 // Execute executes the command
-func Execute() {
-	if err := rootCmd.Execute(); err != nil {
-		log.Fatal(err)
-	}
+func Execute() error {
+	return rootCmd.Execute()
 }

cmd/root_test.go

@@ -0,0 +1,60 @@
+package cmd
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRootNoError(t *testing.T) {
+	a := assert.New(t)
+	err := rootCmd.Execute()
+	a.Nil(err)
+}
+
+func TestRootMissingVerbose(t *testing.T) {
+	a := assert.New(t)
+	cmd := &cobra.Command{}
+	err := rootCmd.PersistentPreRunE(cmd, nil)
+	a.NotNil(err)
+	a.Contains(err.Error(), "flag accessed but not defined: verbose")
+}
+
+func TestRootMissingConfig(t *testing.T) {
+	a := assert.New(t)
+	cmd := &cobra.Command{}
+	cmd.PersistentFlags().BoolP("verbose", "v", false, "Use this to enable verbose mode")
+
+	flags := []string{"--verbose"}
+	err := cmd.ParseFlags(flags)
+	a.Nil(err)
+
+	err = rootCmd.PersistentPreRunE(cmd, nil)
+	a.NotNil(err)
+	a.Contains(err.Error(), "Missing config")
+}
+
+func TestRootLock(t *testing.T) {
+	a := assert.New(t)
+	cmd := &cobra.Command{}
+
+	name, err := ioutil.TempDir("", "blessclient-tests")
+	a.Nil(err)
+	defer os.RemoveAll(name)
+
+	cmd.PersistentFlags().BoolP("verbose", "v", false, "Use this to enable verbose mode")
+	cmd.PersistentFlags().StringP(flagConfig, "c", name, "Use this to override the bless config file.")
+
+	flags := []string{"--verbose", "--config", name}
+	err = cmd.ParseFlags(flags)
+	a.Nil(err)
+
+	err = rootCmd.PersistentPreRunE(cmd, nil)
+	a.Nil(err)
+
+	err = rootCmd.PersistentPostRunE(cmd, nil)
+	a.Nil(err)
+}

cmd/run.go

@@ -16,15 +16,13 @@ import (
 	"github.com/google/uuid"
 	multierror "github.com/hashicorp/go-multierror"
 	"github.com/honeycombio/opencensus-exporter/honeycomb"
-	homedir "github.com/mitchellh/go-homedir"
 	"github.com/pkg/errors"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"go.opencensus.io/trace"
 )
 
 func init() {
-	runCmd.Flags().StringP("config", "c", config.DefaultConfigFile, "Use this to override the bless config file.")
 	rootCmd.AddCommand(runCmd)
 }
 
@@ -38,18 +36,12 @@ var runCmd = &cobra.Command{
 			// Just for telemetry so ignore errors
 			log.Debugf("Failed to generate UUID with error %s", err.Error())
 		}
-
 		log.Debugf("Running blessclient v%s", util.VersionCacheKey())
 		log.Debugf("RunID: %s", id.String())
-
 		ctx := context.Background()
-		configFile, err := cmd.Flags().GetString("config")
+		expandedConfigFile, err := util.GetConfigPath(cmd)
 		if err != nil {
-			return errors.New("Missing config")
-		}
-		expandedConfigFile, err := homedir.Expand(configFile)
-		if err != nil {
-			return errors.Wrapf(err, "Could not expand %s", configFile)
+			return err
 		}
 		log.Debugf("Reading config from %s", expandedConfigFile)
 

main.go

@@ -2,8 +2,11 @@ package main
 
 import (
 	"github.com/chanzuckerberg/blessclient/cmd"
+	"github.com/sirupsen/logrus"
 )
 
 func main() {
-	cmd.Execute()
+	if err := cmd.Execute(); err != nil {
+		logrus.Fatal(err)
+	}
 }

pkg/util/cobra.go

@@ -0,0 +1,20 @@
+package util
+
+import (
+	homedir "github.com/mitchellh/go-homedir"
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+// GetConfigPath gets the config path from a cobra cmd
+func GetConfigPath(cmd *cobra.Command) (string, error) {
+	configFile, err := cmd.Flags().GetString("config")
+	if err != nil {
+		return "", errors.New("Missing config")
+	}
+	expandedConfigFile, err := homedir.Expand(configFile)
+	if err != nil {
+		return "", errors.Wrapf(err, "Could not expand %s", configFile)
+	}
+	return expandedConfigFile, nil
+}