add dispatch idempotency token support in the CLI

.changelog/10930.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+cli: Add `-idempotency-token` option for the `nomad job dispatch` command
+```

api/jobs.go

@@ -813,21 +813,22 @@ type Job struct {
 
 	/* Fields set by server, not sourced from job config file */
 
-	Stop              *bool
-	ParentID          *string
-	Dispatched        bool
-	Payload           []byte
-	ConsulNamespace   *string `mapstructure:"consul_namespace"`
-	VaultNamespace    *string `mapstructure:"vault_namespace"`
-	NomadTokenID      *string `mapstructure:"nomad_token_id"`
-	Status            *string
-	StatusDescription *string
-	Stable            *bool
-	Version           *uint64
-	SubmitTime        *int64
-	CreateIndex       *uint64
-	ModifyIndex       *uint64
-	JobModifyIndex    *uint64
+	Stop                     *bool
+	ParentID                 *string
+	Dispatched               bool
+	DispatchIdempotencyToken *string
+	Payload                  []byte
+	ConsulNamespace          *string `mapstructure:"consul_namespace"`
+	VaultNamespace           *string `mapstructure:"vault_namespace"`
+	NomadTokenID             *string `mapstructure:"nomad_token_id"`
+	Status                   *string
+	StatusDescription        *string
+	Stable                   *bool
+	Version                  *uint64
+	SubmitTime               *int64
+	CreateIndex              *uint64
+	ModifyIndex              *uint64
+	JobModifyIndex           *uint64
 }
 
 // IsPeriodic returns whether a job is periodic.

command/job_dispatch.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/hashicorp/nomad/api"
 	flaghelper "github.com/hashicorp/nomad/helper/flags"
 	"github.com/posener/complete"
 )
@@ -23,6 +24,10 @@ Usage: nomad job dispatch [options] <parameterized job> [input source]
   path to a file. Metadata can be supplied by using the meta flag one or more
   times.
 
+  An optional idempotency token can be used to prevent more than one instance
+  of the job to be dispatched. If an instance with the same token already
+  exists, the command returns without any action.
+
   Upon successful creation, the dispatched job ID will be printed and the
   triggered evaluation will be monitored. This can be disabled by supplying the
   detach flag.
@@ -48,6 +53,10 @@ Dispatch Options:
     the evaluation ID will be printed to the screen, which can be used to
     examine the evaluation using the eval-status command.
 
+  -idempotency-token
+    Optional identifier used to prevent more than one instance of the job from
+    being dispatched.
+
   -verbose
     Display full information.
 `
@@ -61,9 +70,10 @@ func (c *JobDispatchCommand) Synopsis() string {
 func (c *JobDispatchCommand) AutocompleteFlags() complete.Flags {
 	return mergeAutocompleteFlags(c.Meta.AutocompleteFlags(FlagSetClient),
 		complete.Flags{
-			"-meta":    complete.PredictAnything,
-			"-detach":  complete.PredictNothing,
-			"-verbose": complete.PredictNothing,
+			"-meta":              complete.PredictAnything,
+			"-detach":            complete.PredictNothing,
+			"-idempotency-token": complete.PredictAnything,
+			"-verbose":           complete.PredictNothing,
 		})
 }
 
@@ -95,12 +105,14 @@ func (c *JobDispatchCommand) Name() string { return "job dispatch" }
 
 func (c *JobDispatchCommand) Run(args []string) int {
 	var detach, verbose bool
+	var idempotencyToken string
 	var meta []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(&idempotencyToken, "idempotency-token", "", "")
 	flags.Var((*flaghelper.StringFlag)(&meta), "meta", "")
 
 	if err := flags.Parse(args); err != nil {
@@ -159,7 +171,10 @@ func (c *JobDispatchCommand) Run(args []string) int {
 	}
 
 	// Dispatch the job
-	resp, _, err := client.Jobs().Dispatch(job, metaMap, payload, nil)
+	w := &api.WriteOptions{
+		IdempotencyToken: idempotencyToken,
+	}
+	resp, _, err := client.Jobs().Dispatch(job, metaMap, payload, w)
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Failed to dispatch job: %s", err))
 		return 1

command/job_status.go

@@ -189,6 +189,10 @@ func (c *JobStatusCommand) Run(args []string) int {
 		fmt.Sprintf("Parameterized|%v", parameterized),
 	}
 
+	if job.DispatchIdempotencyToken != nil && *job.DispatchIdempotencyToken != "" {
+		basic = append(basic, fmt.Sprintf("Idempotency Token|%v", *job.DispatchIdempotencyToken))
+	}
+
 	if periodic && !parameterized {
 		if *job.Stop {
 			basic = append(basic, "Next Periodic Launch|none (job stopped)")

website/content/api-docs/jobs.mdx

@@ -1617,6 +1617,10 @@ The table below shows this endpoint's support for
 - `:job_id` `(string: <required>)` - Specifies the ID of the job (as specified
   in the job file during submission). This is specified as part of the path.
 
+- `idempotency_token` `(string: "")` - Optional identifier used to prevent more
+  than one instance of the job from being dispatched. This is specified as a
+  URL query parameter.
+
 - `Payload` `(string: "")` - Specifies a base64 encoded string containing the
   payload. This is limited to 16384 bytes (16KiB).
 

website/content/docs/commands/job/dispatch.mdx

@@ -30,6 +30,11 @@ flag one or more times.
 
 The payload has a **size limit of 16384 bytes (16KiB)**.
 
+An optional idempotency token can be specified to prevent dispatching more than
+one instance of the same job. The token can have any value and will be matched
+with existing jobs. If an instance with the same token already exists, the job
+will not be dispatched.
+
 Upon successful creation, the dispatched job ID will be printed and the
 triggered evaluation will be monitored. This can be disabled by supplying the
 detach flag.
@@ -58,6 +63,9 @@ capability for the job's namespace.
   will be output, which can be used to examine the evaluation using the
   [eval status] command
 
+- `-idempotency-token`: Optional identifier used to prevent more than one
+  instance of the job from being dispatched.
+
 - `-verbose`: Show full information.
 
 ## Examples
@@ -109,5 +117,26 @@ Dispatched Job ID = example/dispatch-1485380684-c37b3dba
 Evaluation ID     = d9034c4e
 ```
 
+Dispatch with an idempotency token for the first time:
+
+```shell-session
+$ nomad job dispatch -idempotency-token=prod video-encode video-config.json
+Dispatched Job ID = video-encode/dispatch-1485379325-cb38d00d
+Evaluation ID     = 31199841
+
+==> Monitoring evaluation "31199841"
+    Evaluation triggered by job "example/dispatch-1485379325-cb38d00d"
+    Allocation "8254b85f" created: node "82ff9c50", group "cache"
+    Evaluation status changed: "pending" -> "complete"
+==> Evaluation "31199841" finished with status "complete"
+```
+
+Dispatch with the same idempotency token:
+
+```shell-session
+$ nomad job dispatch -idempotency-token=prod video-encode video-config.json
+Job "video-encode/dispatch-1485379325-cb38d00d" already dispatched with idempotency token "prod".
+```
+
 [eval status]: /docs/commands/eval-status
 [parameterized job]: /docs/job-specification/parameterized 'Nomad parameterized Job Specification'