Merge pull request #2868 from hashicorp/f-feedback

Variety of UX fixes

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## 0.6.0 (Unreleased)
 
+__BACKWARDS INCOMPATIBILITIES:__
+ * cli: When given a prefix that does not resolve to a particular object,
+   commands now return exit code 1 rather than 0.
+
 IMPROVEMENTS:
  * core: Rolling updates based on allocation health [GH-2621, GH-2634, GH-2799]
  * core: New deployment object to track job updates [GH-2621, GH-2634, GH-2799]

command/deployment_fail.go

@@ -42,7 +42,7 @@ func (c *DeploymentFailCommand) Synopsis() string {
 func (c *DeploymentFailCommand) Run(args []string) int {
 	var detach, verbose bool
 
-	flags := c.Meta.FlagSet("deployment resume", FlagSetClient)
+	flags := c.Meta.FlagSet("deployment fail", FlagSetClient)
 	flags.Usage = func() { c.Ui.Output(c.Help()) }
 	flags.BoolVar(&detach, "detach", false, "")
 	flags.BoolVar(&verbose, "verbose", false, "")
@@ -81,8 +81,8 @@ func (c *DeploymentFailCommand) Run(args []string) int {
 	}
 
 	if len(possible) != 0 {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
+		return 1
 	}
 
 	u, _, err := client.Deployments().Fail(deploy.ID, nil)

command/deployment_pause.go

@@ -73,8 +73,8 @@ func (c *DeploymentPauseCommand) Run(args []string) int {
 	}
 
 	if len(possible) != 0 {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
+		return 1
 	}
 
 	if _, _, err := client.Deployments().Pause(deploy.ID, true, nil); err != nil {

command/deployment_promote.go

@@ -30,12 +30,9 @@ General Options:
 
 Promote Options:
 
-  -all
-    All promotes all task groups in the deployment.
-
   -group
 	Group may be specified many times and is used to promote that particular
-	group.
+	group. If no specific groups are specified, all groups are promoted.
 
   -detach
 	Return immediately instead of entering monitor mode. After deployment
@@ -49,16 +46,15 @@ Promote Options:
 }
 
 func (c *DeploymentPromoteCommand) Synopsis() string {
-	return "Manually fail a deployment"
+	return "Promote canaries in a deployment"
 }
 
 func (c *DeploymentPromoteCommand) Run(args []string) int {
-	var all, detach, verbose bool
+	var detach, verbose bool
 	var groups []string
 
-	flags := c.Meta.FlagSet("deployment resume", FlagSetClient)
+	flags := c.Meta.FlagSet("deployment promote", FlagSetClient)
 	flags.Usage = func() { c.Ui.Output(c.Help()) }
-	flags.BoolVar(&all, "all", false, "")
 	flags.BoolVar(&detach, "detach", false, "")
 	flags.BoolVar(&verbose, "verbose", false, "")
 	flags.Var((*flaghelper.StringFlag)(&groups), "group", "")
@@ -73,10 +69,6 @@ func (c *DeploymentPromoteCommand) Run(args []string) int {
 		c.Ui.Error(c.Help())
 		return 1
 	}
-	if !all && len(groups) == 0 {
-		c.Ui.Error("Either -all or one or more -group flags must be specified.")
-		return 1
-	}
 	dID := args[0]
 
 	// Truncate the id unless full length is requested
@@ -100,19 +92,19 @@ func (c *DeploymentPromoteCommand) Run(args []string) int {
 	}
 
 	if len(possible) != 0 {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
+		return 1
 	}
 
 	var u *api.DeploymentUpdateResponse
-	if all {
+	if len(groups) == 0 {
 		u, _, err = client.Deployments().PromoteAll(deploy.ID, nil)
 	} else {
 		u, _, err = client.Deployments().PromoteGroups(deploy.ID, groups, nil)
 	}
 
 	if err != nil {
-		c.Ui.Error(fmt.Sprintf("Error failing deployment: %s", err))
+		c.Ui.Error(fmt.Sprintf("Error promoting deployment: %s", err))
 		return 1
 	}
 

command/deployment_promote_test.go

@@ -27,14 +27,6 @@ func TestDeploymentPromoteCommand_Fails(t *testing.T) {
 	if code := cmd.Run([]string{"-address=nope", "12"}); code != 1 {
 		t.Fatalf("expected exit code 1, got: %d", code)
 	}
-	if out := ui.ErrorWriter.String(); !strings.Contains(out, "flags must be specified") {
-		t.Fatalf("expected missing flags error, got: %s", out)
-	}
-	ui.ErrorWriter.Reset()
-
-	if code := cmd.Run([]string{"-address=nope", "-all", "12"}); code != 1 {
-		t.Fatalf("expected exit code 1, got: %d", code)
-	}
 	if out := ui.ErrorWriter.String(); !strings.Contains(out, "Error retrieving deployment") {
 		t.Fatalf("expected failed query error, got: %s", out)
 	}

command/deployment_resume.go

@@ -79,8 +79,8 @@ func (c *DeploymentResumeCommand) Run(args []string) int {
 	}
 
 	if len(possible) != 0 {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
+		return 1
 	}
 
 	u, _, err := client.Deployments().Pause(deploy.ID, false, nil)

command/deployment_status.go

@@ -84,8 +84,8 @@ func (c *DeploymentStatusCommand) Run(args []string) int {
 	}
 
 	if len(possible) != 0 {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple deployments\n\n%s", formatDeployments(possible, length)))
+		return 1
 	}
 
 	if json || len(tmpl) > 0 {
@@ -177,9 +177,12 @@ func formatDeploymentGroups(d *api.Deployment, uuidLength int) string {
 	if autorevert {
 		rowString += "Auto Revert|"
 	}
+	if canaries {
+		rowString += "Promoted|"
+	}
 	rowString += "Desired|"
 	if canaries {
-		rowString += "Canaries|Promoted|"
+		rowString += "Canaries|"
 	}
 	rowString += "Placed|Healthy|Unhealthy"
 
@@ -191,10 +194,12 @@ func formatDeploymentGroups(d *api.Deployment, uuidLength int) string {
 		if autorevert {
 			row += fmt.Sprintf("%v|", state.AutoRevert)
 		}
+		if canaries {
+			row += fmt.Sprintf("%v|", state.Promoted)
+		}
 		row += fmt.Sprintf("%d|", state.DesiredTotal)
 		if canaries {
 			row += fmt.Sprintf("%d|", state.DesiredCanaries)
-			row += fmt.Sprintf("%v|", state.Promoted)
 		}
 		row += fmt.Sprintf("%d|%d|%d", state.PlacedAllocs, state.HealthyAllocs, state.UnhealthyAllocs)
 		rows[i] = row

command/eval_status.go

@@ -137,8 +137,8 @@ func (c *EvalStatusCommand) Run(args []string) int {
 				failures,
 			)
 		}
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple evaluations\n\n%s", formatList(out)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple evaluations\n\n%s", formatList(out)))
+		return 1
 	}
 
 	// If we are in monitor mode, monitor and exit

command/fs.go

@@ -160,8 +160,8 @@ func (f *FSCommand) Run(args []string) int {
 	if len(allocs) > 1 {
 		// Format the allocs
 		out := formatAllocListStubs(allocs, verbose, length)
-		f.Ui.Output(fmt.Sprintf("Prefix matched multiple allocations\n\n%s", out))
-		return 0
+		f.Ui.Error(fmt.Sprintf("Prefix matched multiple allocations\n\n%s", out))
+		return 1
 	}
 	// Prefix lookup matched a single allocation
 	alloc, _, err := client.Allocations().Info(allocs[0].ID, nil)

command/inspect.go

@@ -23,6 +23,9 @@ General Options:
 
 Inspect Options:
 
+  -version <job version>
+    Display only the history for the given job version.
+
   -json
     Output the job in its JSON format.
 
@@ -38,12 +41,13 @@ func (c *InspectCommand) Synopsis() string {
 
 func (c *InspectCommand) Run(args []string) int {
 	var json bool
-	var tmpl string
+	var tmpl, versionStr string
 
 	flags := c.Meta.FlagSet("inspect", FlagSetClient)
 	flags.Usage = func() { c.Ui.Output(c.Help()) }
 	flags.BoolVar(&json, "json", false, "")
 	flags.StringVar(&tmpl, "t", "", "")
+	flags.StringVar(&versionStr, "version", "", "")
 
 	if err := flags.Parse(args); err != nil {
 		return 1
@@ -93,12 +97,23 @@ func (c *InspectCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
+	}
+
+	var version *uint64
+	if versionStr != "" {
+		v, _, err := parseVersion(versionStr)
+		if err != nil {
+			c.Ui.Error(fmt.Sprintf("Error parsing version value %q: %v", versionStr, err))
+			return 1
+		}
+
+		version = &v
 	}
 
 	// Prefix lookup matched a single job
-	job, _, err := client.Jobs().Info(jobs[0].ID, nil)
+	job, err := getJob(client, jobs[0].ID, version)
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error inspecting job: %s", err))
 		return 1
@@ -132,3 +147,25 @@ func (c *InspectCommand) Run(args []string) int {
 	c.Ui.Output(out)
 	return 0
 }
+
+// getJob retrieves the job optionally at a particular version.
+func getJob(client *api.Client, jobID string, version *uint64) (*api.Job, error) {
+	if version == nil {
+		job, _, err := client.Jobs().Info(jobID, nil)
+		return job, err
+	}
+
+	versions, _, _, err := client.Jobs().Versions(jobID, false, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, j := range versions {
+		if *j.Version != *version {
+			continue
+		}
+		return j, nil
+	}
+
+	return nil, fmt.Errorf("job %q with version %d couldn't be found", jobID, *version)
+}

command/job_deployments.go

@@ -82,8 +82,8 @@ func (c *JobDeploymentsCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
 	}
 	jobID = jobs[0].ID
 

command/job_history.go

@@ -100,8 +100,8 @@ func (c *JobHistoryCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
 	}
 
 	// Prefix lookup matched a single job

command/job_promote.go

@@ -0,0 +1,136 @@
+package command
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/hashicorp/nomad/api"
+	flaghelper "github.com/hashicorp/nomad/helper/flag-helpers"
+)
+
+type JobPromoteCommand struct {
+	Meta
+}
+
+func (c *JobPromoteCommand) Help() string {
+	helpText := `
+Usage: nomad job promote [options] <job id>
+
+Promote is used to promote task groups in the most recent deployment for the
+given job. Promotion should occur when the deployment has placed canaries for a
+task group and those canaries have been deemed healthy. When a task group is
+promoted, the rolling upgrade of the remaining allocations is unblocked. If the
+canaries are found to be unhealthy, the deployment may either be failed using
+the "nomad deployment fail" command, the job can be failed forward by submitting
+a new version or failed backwards by reverting to an older version using the
+"nomad job revert" command.
+
+General Options:
+
+  ` + generalOptionsUsage() + `
+
+Promote Options:
+
+  -group
+	Group may be specified many times and is used to promote that particular
+	group. If no specific groups are specified, all groups are promoted.
+
+  -detach
+	Return immediately instead of entering monitor mode. After deployment
+	resume, the evaluation ID will be printed to the screen, which can be used
+	to examine the evaluation using the eval-status command.
+
+  -verbose
+    Display full information.
+`
+	return strings.TrimSpace(helpText)
+}
+
+func (c *JobPromoteCommand) Synopsis() string {
+	return "Promote a job's canaries"
+}
+
+func (c *JobPromoteCommand) Run(args []string) int {
+	var detach, verbose bool
+	var groups []string
+
+	flags := c.Meta.FlagSet("job promote", FlagSetClient)
+	flags.Usage = func() { c.Ui.Output(c.Help()) }
+	flags.BoolVar(&detach, "detach", false, "")
+	flags.BoolVar(&verbose, "verbose", false, "")
+	flags.Var((*flaghelper.StringFlag)(&groups), "group", "")
+
+	if err := flags.Parse(args); err != nil {
+		return 1
+	}
+
+	// Check that we got no arguments
+	args = flags.Args()
+	if l := len(args); l != 1 {
+		c.Ui.Error(c.Help())
+		return 1
+	}
+
+	// Truncate the id unless full length is requested
+	length := shortId
+	if verbose {
+		length = fullId
+	}
+
+	// Get the HTTP client
+	client, err := c.Meta.Client()
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Error initializing client: %s", err))
+		return 1
+	}
+
+	// Check if the job exists
+	jobID := args[0]
+	jobs, _, err := client.Jobs().PrefixList(jobID)
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Error promoting job: %s", err))
+		return 1
+	}
+	if len(jobs) == 0 {
+		c.Ui.Error(fmt.Sprintf("No job(s) with prefix or id %q found", jobID))
+		return 1
+	}
+	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
+	}
+	jobID = jobs[0].ID
+
+	// Do a prefix lookup
+	deploy, _, err := client.Jobs().LatestDeployment(jobID, nil)
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Error retrieving deployment: %s", err))
+		return 1
+	}
+
+	if deploy == nil {
+		c.Ui.Error(fmt.Sprintf("Job %q has no deployment to promote", jobID))
+		return 1
+	}
+
+	var u *api.DeploymentUpdateResponse
+	if len(groups) == 0 {
+		u, _, err = client.Deployments().PromoteAll(deploy.ID, nil)
+	} else {
+		u, _, err = client.Deployments().PromoteGroups(deploy.ID, groups, nil)
+	}
+
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Error promoting deployment %q for job %q: %s", deploy.ID, jobID, err))
+		return 1
+	}
+
+	// Nothing to do
+	evalCreated := u.EvalID != ""
+	if detach || !evalCreated {
+		return 0
+	}
+
+	mon := newMonitor(c.Ui, client, length)
+	return mon.monitor(u.EvalID, false)
+}

command/job_promote_test.go

@@ -0,0 +1,34 @@
+package command
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mitchellh/cli"
+)
+
+func TestJobPromoteCommand_Implements(t *testing.T) {
+	var _ cli.Command = &JobPromoteCommand{}
+}
+
+func TestJobPromoteCommand_Fails(t *testing.T) {
+	ui := new(cli.MockUi)
+	cmd := &JobPromoteCommand{Meta: Meta{Ui: ui}}
+
+	// Fails on misuse
+	if code := cmd.Run([]string{"some", "bad", "args"}); code != 1 {
+		t.Fatalf("expected exit code 1, got: %d", code)
+	}
+	if out := ui.ErrorWriter.String(); !strings.Contains(out, cmd.Help()) {
+		t.Fatalf("expected help output, got: %s", out)
+	}
+	ui.ErrorWriter.Reset()
+
+	if code := cmd.Run([]string{"-address=nope", "12"}); code != 1 {
+		t.Fatalf("expected exit code 1, got: %d", code)
+	}
+	if out := ui.ErrorWriter.String(); !strings.Contains(out, "Error promoting") {
+		t.Fatalf("expected failed to promote error, got: %s", out)
+	}
+	ui.ErrorWriter.Reset()
+}

command/job_revert.go

@@ -91,8 +91,8 @@ func (c *JobRevertCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
 	}
 
 	// Prefix lookup matched a single job

command/logs.go

@@ -136,8 +136,8 @@ func (l *LogsCommand) Run(args []string) int {
 	if len(allocs) > 1 {
 		// Format the allocs
 		out := formatAllocListStubs(allocs, verbose, length)
-		l.Ui.Output(fmt.Sprintf("Prefix matched multiple allocations\n\n%s", out))
-		return 0
+		l.Ui.Error(fmt.Sprintf("Prefix matched multiple allocations\n\n%s", out))
+		return 1
 	}
 	// Prefix lookup matched a single allocation
 	alloc, _, err := client.Allocations().Info(allocs[0].ID, nil)

command/node_drain.go

@@ -124,8 +124,8 @@ func (c *NodeDrainCommand) Run(args []string) int {
 				node.Status)
 		}
 		// Dump the output
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple nodes\n\n%s", formatList(out)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple nodes\n\n%s", formatList(out)))
+		return 1
 	}
 
 	// Prefix lookup matched a single node

command/node_status.go

@@ -231,8 +231,8 @@ func (c *NodeStatusCommand) Run(args []string) int {
 				node.Status)
 		}
 		// Dump the output
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple nodes\n\n%s", formatList(out)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple nodes\n\n%s", formatList(out)))
+		return 1
 	}
 	// Prefix lookup matched a single node
 	node, _, err := client.Nodes().Info(nodes[0].ID, nil)

command/status.go

@@ -121,8 +121,8 @@ func (c *StatusCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
 	}
 	// Prefix lookup matched a single job
 	job, _, err := client.Jobs().Info(jobs[0].ID, nil)

command/status_test.go

@@ -113,16 +113,18 @@ func TestStatusCommand_Run(t *testing.T) {
 	if !strings.Contains(out, "Created At") {
 		t.Fatal("should have created header")
 	}
+	ui.ErrorWriter.Reset()
 	ui.OutputWriter.Reset()
 
 	// Query jobs with prefix match
-	if code := cmd.Run([]string{"-address=" + url, "job"}); code != 0 {
-		t.Fatalf("expected exit 0, got: %d", code)
+	if code := cmd.Run([]string{"-address=" + url, "job"}); code != 1 {
+		t.Fatalf("expected exit 1, got: %d", code)
 	}
-	out = ui.OutputWriter.String()
+	out = ui.ErrorWriter.String()
 	if !strings.Contains(out, "job1_sfx") || !strings.Contains(out, "job2_sfx") {
 		t.Fatalf("expected job1_sfx and job2_sfx, got: %s", out)
 	}
+	ui.ErrorWriter.Reset()
 	ui.OutputWriter.Reset()
 
 	// Query a single job with prefix match

command/stop.go

@@ -94,8 +94,8 @@ func (c *StopCommand) Run(args []string) int {
 		return 1
 	}
 	if len(jobs) > 1 && strings.TrimSpace(jobID) != jobs[0].ID {
-		c.Ui.Output(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
-		return 0
+		c.Ui.Error(fmt.Sprintf("Prefix matched multiple jobs\n\n%s", createStatusListOutput(jobs)))
+		return 1
 	}
 	// Prefix lookup matched a single job
 	job, _, err := client.Jobs().Info(jobs[0].ID, nil)

commands.go

@@ -144,6 +144,11 @@ func Commands(metaPtr *command.Meta) map[string]cli.CommandFactory {
 				Meta: meta,
 			}, nil
 		},
+		"job promote": func() (cli.Command, error) {
+			return &command.JobPromoteCommand{
+				Meta: meta,
+			}, nil
+		},
 		"job revert": func() (cli.Command, error) {
 			return &command.JobRevertCommand{
 				Meta: meta,

main.go

@@ -30,7 +30,7 @@ func RunCustom(args []string, commands map[string]cli.CommandFactory) int {
 			"deployment resume", "deployment fail", "deployment promote":
 		case "executor":
 		case "fs ls", "fs cat", "fs stat":
-		case "job deployments", "job dispatch", "job history", "job revert":
+		case "job deployments", "job dispatch", "job history", "job promote", "job revert":
 		case "operator raft", "operator raft list-peers", "operator raft remove-peer":
 		case "syslog":
 		default:

nomad/deployment_endpoint.go

@@ -122,7 +122,11 @@ func (d *Deployment) Pause(args *structs.DeploymentPauseRequest, reply *structs.
 	}
 
 	if !deploy.Active() {
-		return fmt.Errorf("can't pause terminal deployment")
+		if args.Pause {
+			return fmt.Errorf("can't pause terminal deployment")
+		}
+
+		return fmt.Errorf("can't resume terminal deployment")
 	}
 
 	// Call into the deployment watcher

website/source/docs/job-specification/update.html.md

@@ -78,6 +78,12 @@ job "docs" {
   last stable job on deployment failure. A job is marked as stable if all the
   allocations as part of its deployment were marked healthy.
 
+- `canary` `(int: 0)` - Specifies that changes to the job that would result in
+  destructive updates should create the specified number of canaries without
+  stopping any previous allocations. Once the operator determines the canaries
+  are healthy, they can be promoted which unblocks a rolling update of the
+  remaining allocations at a rate of `max_parallel`.
+
 - `stagger` `(string: "30s")` - Specifies the delay between migrating
   allocations off nodes marked for draining. This is specified using a label
   suffix like "30s" or "1h".
@@ -120,10 +126,7 @@ update {
 
 This example creates a canary allocation when the job is updated. The canary is
 created without stopping any previous allocations from the job and allows
-operators to determine if the new version of the job should be rolled out. Once
-the operator has determined the new job should be deployed, the deployment can
-be promoted and a rolling update will occur performing 3 updates at a time till
-the remainder of the groups allocations have been rolled to the new version.
+operators to determine if the new version of the job should be rolled out. 
 
 ```hcl
 update {
@@ -132,6 +135,47 @@ update {
 }
 ```
 
+Once the operator has determined the new job should be deployed, the deployment
+can be promoted and a rolling update will occur performing 3 updates at a time
+until the remainder of the groups allocations have been rolled to the new
+version.
+
+```text
+# Promote the canaries for the job.
+$ nomad job promote <job-id>
+```
+
+### Blue/Green Upgrades
+
+By setting the canary count equal to that of the task group, blue/green
+deployments can be achieved. When a new version of the job is submitted, instead
+of doing a rolling upgrade of the existing allocations, the new version of the
+group is deployed along side the existing set. While this duplicates the
+resources required during the upgrade process, it allows very safe deployments
+as the original version of the group is untouched.
+
+```hcl
+group "api-server" {
+    count = 3
+
+    update {
+      canary       = 3
+      max_parallel = 3
+    }
+    ...
+}
+```
+
+Once the operator is satisfied that the new version of the group is stable, the
+group can be promoted which will result in all allocations for the old versions
+of the group to be shutdown. This completes the upgrade from blue to green, or
+old to new version.
+
+```text
+# Promote the canaries for the job.
+$ nomad job promote <job-id>
+```
+
 ### Serial Upgrades
 
 This example uses a serial upgrade strategy, meaning exactly one task group will