[ECS-Plugin] Implement Livestate Plugin

pkg/app/pipedv1/plugin/ecs/deployment/test_helper.go

@@ -41,11 +41,13 @@ func (f *fakeLogPersister) Complete(time.Duration) error      { return nil }
 type mockECSClient struct {
 	CreateServiceFunc               func(ctx context.Context, service types.Service) (*types.Service, error)
 	UpdateServiceFunc               func(ctx context.Context, service types.Service) (*types.Service, error)
+	DescribeServiceFunc             func(ctx context.Context, service types.Service) (*types.Service, error)
 	GetServiceTaskSetsFunc          func(ctx context.Context, service types.Service) ([]types.TaskSet, error)
 	GetPrimaryTaskSetFunc           func(ctx context.Context, service types.Service) (*types.TaskSet, error)
 	CreateTaskSetFunc               func(ctx context.Context, service types.Service, taskDefinition types.TaskDefinition, targetGroup *types.LoadBalancer, scale float64) (*types.TaskSet, error)
 	UpdateServicePrimaryTaskSetFunc func(ctx context.Context, service types.Service, taskSet types.TaskSet) (*types.TaskSet, error)
 	DeleteTaskSetFunc               func(ctx context.Context, taskSet types.TaskSet) error
+	GetTasksFunc                    func(ctx context.Context, service types.Service) ([]types.Task, error)
 	ServiceExistsFunc               func(ctx context.Context, cluster, serviceName string) (bool, error)
 	GetServiceStatusFunc            func(ctx context.Context, cluster, serviceName string) (string, error)
 	WaitServiceStableFunc           func(ctx context.Context, cluster, serviceName string) error
@@ -65,6 +67,9 @@ func (m *mockECSClient) CreateService(ctx context.Context, service types.Service
 func (m *mockECSClient) UpdateService(ctx context.Context, service types.Service) (*types.Service, error) {
 	return m.UpdateServiceFunc(ctx, service)
 }
+func (m *mockECSClient) DescribeService(ctx context.Context, service types.Service) (*types.Service, error) {
+	return m.DescribeServiceFunc(ctx, service)
+}
 func (m *mockECSClient) GetServiceTaskSets(ctx context.Context, service types.Service) ([]types.TaskSet, error) {
 	return m.GetServiceTaskSetsFunc(ctx, service)
 }
@@ -80,6 +85,9 @@ func (m *mockECSClient) UpdateServicePrimaryTaskSet(ctx context.Context, service
 func (m *mockECSClient) DeleteTaskSet(ctx context.Context, taskSet types.TaskSet) error {
 	return m.DeleteTaskSetFunc(ctx, taskSet)
 }
+func (m *mockECSClient) GetTasks(ctx context.Context, service types.Service) ([]types.Task, error) {
+	return m.GetTasksFunc(ctx, service)
+}
 func (m *mockECSClient) ServiceExists(ctx context.Context, cluster, serviceName string) (bool, error) {
 	return m.ServiceExistsFunc(ctx, cluster, serviceName)
 }

pkg/app/pipedv1/plugin/ecs/livestate/fetcher.go

@@ -0,0 +1,65 @@
+// Copyright 2026 The PipeCD Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package livestate
+
+import (
+	"context"
+
+	"github.com/aws/aws-sdk-go-v2/service/ecs/types"
+
+	"github.com/pipe-cd/pipecd/pkg/app/pipedv1/plugin/ecs/provider"
+)
+
+// ECSFetcher fetches the current state of an ECS application's resources
+type ECSFetcher struct {
+	client provider.Client
+}
+
+// QueryResources fetches the live Service, its PipeCD-managed TaskSets, and all Tasks for the given service descriptor
+func (w *ECSFetcher) FetchResources(ctx context.Context, service types.Service) (*queryResourcesResult, error) {
+	liveService, err := w.client.DescribeService(ctx, service)
+	if err != nil {
+		return nil, err
+	}
+
+	// GetServiceTaskSets filters out DRAINING task sets and task sets not created by Pipecd,
+	// so the result only contains task sets that Pipecd is responsible for
+	tasksets, err := w.client.GetServiceTaskSets(ctx, *liveService)
+	if err != nil {
+		return nil, err
+	}
+
+	// Tasks are fetched for the whole service rather than per task set.
+	// Grouping tasks under their parent task set is deferred to the caller.
+	tasks, err := w.client.GetTasks(ctx, *liveService)
+	if err != nil {
+		return nil, err
+	}
+
+	return &queryResourcesResult{
+		Service:  liveService,
+		TaskSets: tasksets,
+		Tasks:    tasks,
+	}, nil
+}
+
+// queryResourcesResult holds the raw AWS objects for a single ECS application.
+//
+// Tasks are a flat list, not group by taskset ID yet
+type queryResourcesResult struct {
+	Service  *types.Service
+	TaskSets []types.TaskSet
+	Tasks    []types.Task
+}