client: add NOMAD_SHORT_ALLOC_ID allocation env var. (#12603)

.changelog/12603.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+client: Added `NOMAD_SHORT_ALLOC_ID` allocation env var
+```

client/taskenv/env.go

@@ -47,6 +47,10 @@ const (
 	// AllocID is the environment variable for passing the allocation ID.
 	AllocID = "NOMAD_ALLOC_ID"
 
+	// ShortAllocID is the environment variable for passing the short version
+	// of the allocation ID.
+	ShortAllocID = "NOMAD_SHORT_ALLOC_ID"
+
 	// AllocName is the environment variable for passing the allocation name.
 	AllocName = "NOMAD_ALLOC_NAME"
 
@@ -505,6 +509,7 @@ func (b *Builder) buildEnv(allocDir, localDir, secretsDir string,
 	// Add the task metadata
 	if b.allocId != "" {
 		envMap[AllocID] = b.allocId
+		envMap[ShortAllocID] = b.allocId[:8]
 	}
 	if b.allocName != "" {
 		envMap[AllocName] = b.allocName

client/taskenv/env_test.go

@@ -238,6 +238,7 @@ func TestEnvironment_AsList(t *testing.T) {
 		"NOMAD_JOB_NAME=my-job",
 		fmt.Sprintf("NOMAD_JOB_PARENT_ID=%s", a.Job.ParentID),
 		fmt.Sprintf("NOMAD_ALLOC_ID=%s", a.ID),
+		fmt.Sprintf("NOMAD_SHORT_ALLOC_ID=%s", a.ID[:8]),
 		"NOMAD_ALLOC_INDEX=0",
 	}
 	sort.Strings(act)
@@ -404,6 +405,7 @@ func TestEnvironment_AllValues(t *testing.T) {
 		"NOMAD_JOB_NAME":                            "my-job",
 		"NOMAD_JOB_PARENT_ID":                       a.Job.ParentID,
 		"NOMAD_ALLOC_ID":                            a.ID,
+		"NOMAD_SHORT_ALLOC_ID":                      a.ID[:8],
 		"NOMAD_ALLOC_INDEX":                         "0",
 		"NOMAD_PORT_connect_proxy_testconnect":      "9999",
 		"NOMAD_HOST_PORT_connect_proxy_testconnect": "9999",

website/content/partials/envvars.mdx

@@ -69,6 +69,12 @@
       </td>
       <td>Allocation ID of the task</td>
     </tr>
+    <tr>
+      <td>
+        <code>NOMAD_SHORT_ALLOC_ID</code>
+      </td>
+      <td>The first 8 characters of the allocation ID of the task</td>
+    </tr>
     <tr>
       <td>
         <code>NOMAD_ALLOC_NAME</code>
@@ -166,7 +172,7 @@
       </td>
     </tr>
     <tr>
-      <th colspan="2">Network-related Variables</th>
+      <th colSpan="2">Network-related Variables</th>
     </tr>
     <tr>
       <td>
@@ -300,7 +306,7 @@
         </td>
       </tr>
     <tr>
-      <th colspan="2">Consul-related Variables (only set for connect native tasks)</th>
+      <th colSpan="2">Consul-related Variables (only set for connect native tasks)</th>
     </tr>
     <tr>
       <td>