start: allow users to call job start command to start stopped jobs

.changelog/24150.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+cli: Added job start command to allow starting a stopped job from the cli
+```

command/commands.go

@@ -521,6 +521,11 @@ func Commands(metaPtr *Meta, agentUi cli.Ui) map[string]cli.CommandFactory {
 				Meta: meta,
 			}, nil
 		},
+		"job start": func() (cli.Command, error) {
+			return &JobStartCommand{
+				Meta: meta,
+			}, nil
+		},
 		"job tag": func() (cli.Command, error) {
 			return &JobTagCommand{
 				Meta: meta,
@@ -1101,6 +1106,11 @@ func Commands(metaPtr *Meta, agentUi cli.Ui) map[string]cli.CommandFactory {
 				Meta: meta,
 			}, nil
 		},
+		"start": func() (cli.Command, error) {
+			return &JobStartCommand{
+				Meta: meta,
+			}, nil
+		},
 		"system": func() (cli.Command, error) {
 			return &SystemCommand{
 				Meta: meta,

command/job_start.go

@@ -0,0 +1,240 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package command
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/hashicorp/nomad/api"
+	"github.com/hashicorp/nomad/api/contexts"
+	"github.com/posener/complete"
+)
+
+type JobStartCommand struct {
+	Meta
+	versionSelected uint64
+}
+
+func (c *JobStartCommand) Help() string {
+	helpText := `
+Usage: nomad job start [options] <job>
+Alias: nomad start
+
+  Start an existing stopped job. This command is used to start a previously stopped job's
+  most recent version. Upon successful start, an interactive
+  monitor session will start to display log lines as the job starts its
+  allocations based on its most recent version. It is safe to exit the monitor
+  early using ctrl+c.
+
+  When ACLs are enabled, this command requires a token with the 'submit-job'
+  and 'read-job' capabilities for the job's namespace. The 'list-jobs'
+  capability is required to run the command with job prefixes instead of exact
+  job IDs.
+
+General Options:
+
+  ` + generalOptionsUsage(usageOptsDefault) + `
+
+Start Options:
+
+  -detach
+    Return immediately instead of entering monitor mode. After the
+    job start command is submitted, a new evaluation ID is printed to the
+    screen, which can be used to examine the evaluation using the eval-status
+    command.
+
+  -consul-token
+   The Consul token used to verify that the caller has access to the Service
+   Identity policies associated in the targeted version of the job.
+
+  -vault-token
+   The Vault token used to verify that the caller has access to the Vault
+   policies in the targeted version of the job.
+
+  -verbose
+    Display full information.
+`
+	return strings.TrimSpace(helpText)
+}
+
+func (c *JobStartCommand) Synopsis() string {
+	return "Start a stopped job"
+}
+
+func (c *JobStartCommand) AutocompleteFlags() complete.Flags {
+	return mergeAutocompleteFlags(c.Meta.AutocompleteFlags(FlagSetClient),
+		complete.Flags{
+			"-detach":  complete.PredictNothing,
+			"-verbose": complete.PredictNothing,
+		})
+}
+
+func (c *JobStartCommand) AutocompleteArgs() complete.Predictor {
+	return complete.PredictFunc(func(a complete.Args) []string {
+		client, err := c.Meta.Client()
+		if err != nil {
+			return nil
+		}
+
+		resp, _, err := client.Search().PrefixSearch(a.Last, contexts.Jobs, nil)
+		if err != nil {
+			return []string{}
+		}
+		return resp.Matches[contexts.Jobs]
+	})
+}
+func (c *JobStartCommand) Name() string { return "job start" }
+
+func (c *JobStartCommand) Run(args []string) int {
+	var detach, verbose bool
+	var consulToken, vaultToken string
+
+	flags := c.Meta.FlagSet(c.Name(), FlagSetClient)
+	flags.Usage = func() { c.Ui.Output(c.Help()) }
+	flags.BoolVar(&detach, "detach", false, "")
+	flags.BoolVar(&verbose, "verbose", false, "")
+	flags.StringVar(&consulToken, "consul-token", "", "")
+	flags.StringVar(&vaultToken, "vault-token", "", "")
+
+	if err := flags.Parse(args); err != nil {
+		return 1
+	}
+
+	// Check that we got at least one job
+	args = flags.Args()
+	if len(args) < 1 {
+		c.Ui.Error("This command takes at least one argument: <job>")
+		c.Ui.Error(commandErrorText(c))
+		return 1
+	}
+
+	var jobIDs []string
+	for _, jobID := range flags.Args() {
+		jobIDs = append(jobIDs, strings.TrimSpace(jobID))
+	}
+
+	// Get the HTTP client
+	client, err := c.Meta.Client()
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf("Error initializing client: %s", err))
+		return 1
+	}
+
+	statusCh := make(chan int, len(jobIDs))
+	var wg sync.WaitGroup
+
+	for _, jobIDPrefix := range jobIDs {
+
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			// Truncate the id unless full length is requested
+			length := shortId
+			if verbose {
+				length = fullId
+			}
+
+			job, err := c.JobByPrefix(client, jobIDPrefix, nil)
+			if err != nil {
+				c.Ui.Error(err.Error())
+				statusCh <- 1
+				return
+			}
+
+			if *job.Status != "dead" {
+				c.Ui.Info(fmt.Sprintf("Job  %v has not been stopped and has the following status: %v", *job.Name, *job.Status))
+				statusCh <- 0
+				return
+
+			}
+
+			// Get all versions associated to current job
+			q := &api.QueryOptions{Namespace: *job.Namespace}
+
+			versions, _, _, err := client.Jobs().Versions(*job.ID, true, q)
+			if err != nil {
+				c.Ui.Error(fmt.Sprintf("Error retrieving job versions: %s", err))
+				statusCh <- 1
+			}
+
+			// Find the most recent version for this job that has not been stopped
+			var chosenVersion uint64
+			versionAvailable := false
+			for i := range versions {
+				if !*versions[i].Stop {
+					chosenVersion = *versions[i].Version
+					versionAvailable = true
+					break
+				}
+
+			}
+			c.versionSelected = chosenVersion
+
+			if !versionAvailable {
+				c.Ui.Error(fmt.Sprintf("No previous available versions of job %v", *job.Name))
+				statusCh <- 1
+				return
+			}
+
+			if consulToken == "" {
+				consulToken = os.Getenv("CONSUL_HTTP_TOKEN")
+			}
+
+			if vaultToken == "" {
+				vaultToken = os.Getenv("VAULT_TOKEN")
+			}
+
+			// Revert to most recent running version!
+			m := &api.WriteOptions{Namespace: *job.Namespace}
+
+			resp, _, err := client.Jobs().Revert(*job.ID, chosenVersion, nil, m, consulToken, vaultToken)
+			if err != nil {
+				c.Ui.Error(fmt.Sprintf("Error retrieving job version %v for job %s: %s,", chosenVersion, *job.ID, err))
+				statusCh <- 1
+				return
+			}
+
+			// Nothing to do: periodic or dispatch job
+			evalCreated := resp.EvalID != ""
+
+			if !evalCreated {
+				statusCh <- 0
+				return
+			}
+
+			if detach {
+				c.Ui.Output("Evaluation ID: " + resp.EvalID)
+				statusCh <- 0
+				return
+			}
+
+			mon := newMonitor(c.Ui, client, length)
+			statusCh <- mon.monitor(resp.EvalID)
+
+		}()
+	}
+	// users will still see
+	// errors if any while we
+	// wait for the goroutines
+	// to finish processing
+	wg.Wait()
+
+	// close the channel to ensure
+	// the range statement below
+	// doesn't go on indefinitely
+	close(statusCh)
+
+	// return a non-zero exit code
+	// if even a single job start fails
+	for status := range statusCh {
+		if status != 0 {
+			return status
+		}
+	}
+	return 0
+}