filter warm-pool activities from status check in aws-asg target

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## UNRELEASED
 
+BUG FIXES:
+* plugin/target/aws-asg: Ignore warm pool activities when determining ASG readiness [[GH-1151]](https://github.com/hashicorp/nomad-autoscaler/pull/1151)
+
 ## 0.4.8 (November 13, 2025)
 
 IMPROVEMENTS:

plugins/builtin/target/aws-asg/plugin/plugin.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/aws/aws-sdk-go-v2/service/autoscaling"
 	"github.com/aws/aws-sdk-go-v2/service/autoscaling/types"
@@ -270,9 +271,24 @@ func (t *TargetPlugin) calculateDirection(asgDesired, strategyDesired int64) (in
 	return 0, ""
 }
 
+func warmPoolActivity(activity types.Activity) bool {
+	if activity.Description == nil {
+		return false
+	}
+
+	desc := *activity.Description
+	return strings.Contains(desc, "Launching a new EC2 instance into warm pool:") ||
+		strings.Contains(desc, "Terminating EC2 instance from warm pool:")
+}
+
 // processLastActivity updates the status object based on the details within
 // the last scaling activity.
 func processLastActivity(activity types.Activity, status *sdk.TargetStatus) {
+	// Warm pool activities are not considered scaling activities in the context of
+	// scaling the asg in or out, so we skip them.
+	if warmPoolActivity(activity) {
+		return
+	}
 
 	// If the last activities progress is not nil then check whether this
 	// finished or not. In the event there is a current activity in progress

plugins/builtin/target/aws-asg/plugin/plugin_test.go

@@ -55,6 +55,57 @@ func TestTargetPlugin_calculateDirection(t *testing.T) {
 	}
 }
 
+func Test_warmPoolActivity(t *testing.T) {
+	testCases := []struct {
+		inputActivity    types.Activity
+		expectedResponse bool
+		name             string
+	}{
+		{
+			inputActivity: types.Activity{
+				Description: ptr.Of("Launching a new EC2 instance into warm pool: i-0b22a22eec53b9321"),
+			},
+			expectedResponse: true,
+			name:             "instance launched into warm pool",
+		},
+		{
+			inputActivity: types.Activity{
+				Description: ptr.Of("Terminating EC2 instance from warm pool: i-0b22a22eec53b9321"),
+			},
+			expectedResponse: true,
+			name:             "instance terminated from warm pool",
+		},
+		{
+			inputActivity: types.Activity{
+				Description: ptr.Of("Launching a new EC2 instance from warm pool: i-0b22a22eec53b9321"),
+			},
+			expectedResponse: false,
+			name:             "instance launched into ASG from warm pool",
+		},
+		{
+			inputActivity: types.Activity{
+				Description: nil,
+			},
+			expectedResponse: false,
+			name:             "nil description",
+		},
+		{
+			inputActivity: types.Activity{
+				Description: ptr.Of(""),
+			},
+			expectedResponse: false,
+			name:             "empty description",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			res := warmPoolActivity(tc.inputActivity)
+			assert.Equal(t, tc.expectedResponse, res, tc.name)
+		})
+	}
+}
+
 func Test_processLastActivity(t *testing.T) {
 
 	testTime := time.Date(2020, time.April, 13, 8, 4, 0, 0, time.UTC)
@@ -114,6 +165,40 @@ func Test_processLastActivity(t *testing.T) {
 			},
 			name: "latest activity all nils",
 		},
+		{
+			inputActivity: types.Activity{
+				Progress:    ptr.Of(int32(75)),
+				Description: ptr.Of("Launching a new EC2 instance into warm pool:"),
+			},
+			inputStatus: &sdk.TargetStatus{
+				Ready: true,
+				Count: 1,
+				Meta:  map[string]string{},
+			},
+			expectedStatus: &sdk.TargetStatus{
+				Ready: true,
+				Count: 1,
+				Meta:  map[string]string{},
+			},
+			name: "latest activity was instance launched into warm pool",
+		},
+		{
+			inputActivity: types.Activity{
+				Progress:    ptr.Of(int32(75)),
+				Description: ptr.Of("Terminating EC2 instance from warm pool:"),
+			},
+			inputStatus: &sdk.TargetStatus{
+				Ready: true,
+				Count: 1,
+				Meta:  map[string]string{},
+			},
+			expectedStatus: &sdk.TargetStatus{
+				Ready: true,
+				Count: 1,
+				Meta:  map[string]string{},
+			},
+			name: "latest activity was instance terminated from warm pool",
+		},
 	}
 
 	for _, tc := range testCases {