Feature: Ephemeral action runners (#33570)

* This includes a runner mock test for hardend PickTask behavior like
described in my proposal
* Runner register ephemeral flag introduced in
https://gitea.com/gitea/act_runner/pulls/649

Closes #32461

models/actions/runner.go

@@ -57,6 +57,8 @@ type ActionRunner struct {
 
 	// Store labels defined in state file (default: .runner file) of `act_runner`
 	AgentLabels []string `xorm:"TEXT"`
+	// Store if this is a runner that only ever get one single job assigned
+	Ephemeral bool `xorm:"ephemeral NOT NULL DEFAULT false"`
 
 	Created timeutil.TimeStamp `xorm:"created"`
 	Updated timeutil.TimeStamp `xorm:"updated"`

models/migrations/migrations.go

@@ -375,6 +375,7 @@ func prepareMigrationTasks() []*migration {
 		newMigration(312, "Add DeleteBranchAfterMerge to AutoMerge", v1_24.AddDeleteBranchAfterMergeForAutoMerge),
 		newMigration(313, "Move PinOrder from issue table to a new table issue_pin", v1_24.MovePinOrderToTableIssuePin),
 		newMigration(314, "Update OwnerID as zero for repository level action tables", v1_24.UpdateOwnerIDOfRepoLevelActionsTables),
+		newMigration(315, "Add Ephemeral to ActionRunner", v1_24.AddEphemeralToActionRunner),
 	}
 	return preparedMigrations
 }

models/migrations/v1_24/v315.go

@@ -0,0 +1,16 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_24 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+func AddEphemeralToActionRunner(x *xorm.Engine) error {
+	type ActionRunner struct {
+		Ephemeral bool `xorm:"ephemeral NOT NULL DEFAULT false"`
+	}
+
+	return x.Sync(new(ActionRunner))
+}

routers/api/actions/runner/runner.go

@@ -78,6 +78,7 @@ func (s *Service) Register(
 		RepoID:      runnerToken.RepoID,
 		Version:     req.Msg.Version,
 		AgentLabels: labels,
+		Ephemeral:   req.Msg.Ephemeral,
 	}
 	if err := runner.GenerateToken(); err != nil {
 		return nil, errors.New("can't generate token")
@@ -96,12 +97,13 @@ func (s *Service) Register(
 
 	res := connect.NewResponse(&runnerv1.RegisterResponse{
 		Runner: &runnerv1.Runner{
-			Id:      runner.ID,
-			Uuid:    runner.UUID,
-			Token:   runner.Token,
-			Name:    runner.Name,
-			Version: runner.Version,
-			Labels:  runner.AgentLabels,
+			Id:        runner.ID,
+			Uuid:      runner.UUID,
+			Token:     runner.Token,
+			Name:      runner.Name,
+			Version:   runner.Version,
+			Labels:    runner.AgentLabels,
+			Ephemeral: runner.Ephemeral,
 		},
 	})
 

services/actions/cleanup.go

@@ -9,14 +9,17 @@ import (
 	"time"
 
 	actions_model "code.gitea.io/gitea/models/actions"
+	"code.gitea.io/gitea/models/db"
 	actions_module "code.gitea.io/gitea/modules/actions"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/storage"
 	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/builder"
 )
 
-// Cleanup removes expired actions logs, data and artifacts
+// Cleanup removes expired actions logs, data, artifacts and used ephemeral runners
 func Cleanup(ctx context.Context) error {
 	// clean up expired artifacts
 	if err := CleanupArtifacts(ctx); err != nil {
@@ -28,6 +31,11 @@ func Cleanup(ctx context.Context) error {
 		return fmt.Errorf("cleanup logs: %w", err)
 	}
 
+	// clean up old ephemeral runners
+	if err := CleanupEphemeralRunners(ctx); err != nil {
+		return fmt.Errorf("cleanup old ephemeral runners: %w", err)
+	}
+
 	return nil
 }
 
@@ -123,3 +131,20 @@ func CleanupLogs(ctx context.Context) error {
 	log.Info("Removed %d logs", count)
 	return nil
 }
+
+// CleanupEphemeralRunners removes used ephemeral runners which are no longer able to process jobs
+func CleanupEphemeralRunners(ctx context.Context) error {
+	subQuery := builder.Select("`action_runner`.id").
+		From(builder.Select("*").From("`action_runner`"), "`action_runner`"). // mysql needs this redundant subquery
+		Join("INNER", "`action_task`", "`action_task`.`runner_id` = `action_runner`.`id`").
+		Where(builder.Eq{"`action_runner`.`ephemeral`": true}).
+		And(builder.NotIn("`action_task`.`status`", actions_model.StatusWaiting, actions_model.StatusRunning, actions_model.StatusBlocked))
+	b := builder.Delete(builder.In("id", subQuery)).From("`action_runner`")
+	res, err := db.GetEngine(ctx).Exec(b)
+	if err != nil {
+		return fmt.Errorf("find runners: %w", err)
+	}
+	affected, _ := res.RowsAffected()
+	log.Info("Removed %d runners", affected)
+	return nil
+}

services/actions/task.go

@@ -23,6 +23,26 @@ func PickTask(ctx context.Context, runner *actions_model.ActionRunner) (*runnerv
 		actionTask *actions_model.ActionTask
 	)
 
+	if runner.Ephemeral {
+		var task actions_model.ActionTask
+		has, err := db.GetEngine(ctx).Where("runner_id = ?", runner.ID).Get(&task)
+		// Let the runner retry the request, do not allow to proceed
+		if err != nil {
+			return nil, false, err
+		}
+		if has {
+			if task.Status == actions_model.StatusWaiting || task.Status == actions_model.StatusRunning || task.Status == actions_model.StatusBlocked {
+				return nil, false, nil
+			}
+			// task has been finished, remove it
+			_, err = db.DeleteByID[actions_model.ActionRunner](ctx, runner.ID)
+			if err != nil {
+				return nil, false, err
+			}
+			return nil, false, fmt.Errorf("runner has been removed")
+		}
+	}
+
 	if err := db.WithTx(ctx, func(ctx context.Context) error {
 		t, ok, err := actions_model.CreateTaskForRunner(ctx, runner)
 		if err != nil {

tests/integration/actions_job_test.go

@@ -21,8 +21,10 @@ import (
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
+	actions_service "code.gitea.io/gitea/services/actions"
 
 	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
+	"connectrpc.com/connect"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -132,7 +134,7 @@ jobs:
 
 		apiRepo := createActionsTestRepo(t, token, "actions-jobs-with-needs", false)
 		runner := newMockRunner()
-		runner.registerAsRepoRunner(t, user2.Name, apiRepo.Name, "mock-runner", []string{"ubuntu-latest"})
+		runner.registerAsRepoRunner(t, user2.Name, apiRepo.Name, "mock-runner", []string{"ubuntu-latest"}, false)
 
 		for _, tc := range testCases {
 			t.Run(fmt.Sprintf("test %s", tc.treePath), func(t *testing.T) {
@@ -318,7 +320,7 @@ jobs:
 
 		apiRepo := createActionsTestRepo(t, token, "actions-jobs-outputs-with-matrix", false)
 		runner := newMockRunner()
-		runner.registerAsRepoRunner(t, user2.Name, apiRepo.Name, "mock-runner", []string{"ubuntu-latest"})
+		runner.registerAsRepoRunner(t, user2.Name, apiRepo.Name, "mock-runner", []string{"ubuntu-latest"}, false)
 
 		for _, tc := range testCases {
 			t.Run(fmt.Sprintf("test %s", tc.treePath), func(t *testing.T) {
@@ -363,7 +365,7 @@ func TestActionsGiteaContext(t *testing.T) {
 		user2APICtx := NewAPITestContext(t, baseRepo.OwnerName, baseRepo.Name, auth_model.AccessTokenScopeWriteRepository)
 
 		runner := newMockRunner()
-		runner.registerAsRepoRunner(t, baseRepo.OwnerName, baseRepo.Name, "mock-runner", []string{"ubuntu-latest"})
+		runner.registerAsRepoRunner(t, baseRepo.OwnerName, baseRepo.Name, "mock-runner", []string{"ubuntu-latest"}, false)
 
 		// init the workflow
 		wfTreePath := ".gitea/workflows/pull.yml"
@@ -437,6 +439,156 @@ jobs:
 	})
 }
 
+// Ephemeral
+func TestActionsGiteaContextEphemeral(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, u *url.URL) {
+		user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+		user2Session := loginUser(t, user2.Name)
+		user2Token := getTokenForLoggedInUser(t, user2Session, auth_model.AccessTokenScopeWriteRepository, auth_model.AccessTokenScopeWriteUser)
+
+		apiBaseRepo := createActionsTestRepo(t, user2Token, "actions-gitea-context", false)
+		baseRepo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: apiBaseRepo.ID})
+		user2APICtx := NewAPITestContext(t, baseRepo.OwnerName, baseRepo.Name, auth_model.AccessTokenScopeWriteRepository)
+
+		runner := newMockRunner()
+		runner.registerAsRepoRunner(t, baseRepo.OwnerName, baseRepo.Name, "mock-runner", []string{"ubuntu-latest"}, true)
+
+		// verify CleanupEphemeralRunners does not remove this runner
+		err := actions_service.CleanupEphemeralRunners(t.Context())
+		assert.NoError(t, err)
+
+		// init the workflow
+		wfTreePath := ".gitea/workflows/pull.yml"
+		wfFileContent := `name: Pull Request
+on: pull_request
+jobs:
+  wf1-job:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo 'test the pull'
+  wf2-job:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo 'test the pull'
+`
+		opts := getWorkflowCreateFileOptions(user2, baseRepo.DefaultBranch, fmt.Sprintf("create %s", wfTreePath), wfFileContent)
+		createWorkflowFile(t, user2Token, baseRepo.OwnerName, baseRepo.Name, wfTreePath, opts)
+		// user2 creates a pull request
+		doAPICreateFile(user2APICtx, "user2-patch.txt", &api.CreateFileOptions{
+			FileOptions: api.FileOptions{
+				NewBranchName: "user2/patch-1",
+				Message:       "create user2-patch.txt",
+				Author: api.Identity{
+					Name:  user2.Name,
+					Email: user2.Email,
+				},
+				Committer: api.Identity{
+					Name:  user2.Name,
+					Email: user2.Email,
+				},
+				Dates: api.CommitDateOptions{
+					Author:    time.Now(),
+					Committer: time.Now(),
+				},
+			},
+			ContentBase64: base64.StdEncoding.EncodeToString([]byte("user2-fix")),
+		})(t)
+		apiPull, err := doAPICreatePullRequest(user2APICtx, baseRepo.OwnerName, baseRepo.Name, baseRepo.DefaultBranch, "user2/patch-1")(t)
+		assert.NoError(t, err)
+		task := runner.fetchTask(t)
+		gtCtx := task.Context.GetFields()
+		actionTask := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionTask{ID: task.Id})
+		actionRunJob := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRunJob{ID: actionTask.JobID})
+		actionRun := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRun{ID: actionRunJob.RunID})
+		assert.NoError(t, actionRun.LoadAttributes(t.Context()))
+
+		assert.Equal(t, user2.Name, gtCtx["actor"].GetStringValue())
+		assert.Equal(t, setting.AppURL+"api/v1", gtCtx["api_url"].GetStringValue())
+		assert.Equal(t, apiPull.Base.Ref, gtCtx["base_ref"].GetStringValue())
+		runEvent := map[string]any{}
+		assert.NoError(t, json.Unmarshal([]byte(actionRun.EventPayload), &runEvent))
+		assert.True(t, reflect.DeepEqual(gtCtx["event"].GetStructValue().AsMap(), runEvent))
+		assert.Equal(t, actionRun.TriggerEvent, gtCtx["event_name"].GetStringValue())
+		assert.Equal(t, apiPull.Head.Ref, gtCtx["head_ref"].GetStringValue())
+		assert.Equal(t, actionRunJob.JobID, gtCtx["job"].GetStringValue())
+		assert.Equal(t, actionRun.Ref, gtCtx["ref"].GetStringValue())
+		assert.Equal(t, (git.RefName(actionRun.Ref)).ShortName(), gtCtx["ref_name"].GetStringValue())
+		assert.False(t, gtCtx["ref_protected"].GetBoolValue())
+		assert.Equal(t, string((git.RefName(actionRun.Ref)).RefType()), gtCtx["ref_type"].GetStringValue())
+		assert.Equal(t, actionRun.Repo.OwnerName+"/"+actionRun.Repo.Name, gtCtx["repository"].GetStringValue())
+		assert.Equal(t, actionRun.Repo.OwnerName, gtCtx["repository_owner"].GetStringValue())
+		assert.Equal(t, actionRun.Repo.HTMLURL(), gtCtx["repositoryUrl"].GetStringValue())
+		assert.Equal(t, fmt.Sprint(actionRunJob.RunID), gtCtx["run_id"].GetStringValue())
+		assert.Equal(t, fmt.Sprint(actionRun.Index), gtCtx["run_number"].GetStringValue())
+		assert.Equal(t, fmt.Sprint(actionRunJob.Attempt), gtCtx["run_attempt"].GetStringValue())
+		assert.Equal(t, "Actions", gtCtx["secret_source"].GetStringValue())
+		assert.Equal(t, setting.AppURL, gtCtx["server_url"].GetStringValue())
+		assert.Equal(t, actionRun.CommitSHA, gtCtx["sha"].GetStringValue())
+		assert.Equal(t, actionRun.WorkflowID, gtCtx["workflow"].GetStringValue())
+		assert.Equal(t, setting.Actions.DefaultActionsURL.URL(), gtCtx["gitea_default_actions_url"].GetStringValue())
+		token := gtCtx["token"].GetStringValue()
+		assert.Equal(t, actionTask.TokenLastEight, token[len(token)-8:])
+
+		// verify CleanupEphemeralRunners does not remove this runner
+		err = actions_service.CleanupEphemeralRunners(t.Context())
+		assert.NoError(t, err)
+
+		resp, err := runner.client.runnerServiceClient.FetchTask(t.Context(), connect.NewRequest(&runnerv1.FetchTaskRequest{
+			TasksVersion: 0,
+		}))
+		assert.NoError(t, err)
+		assert.Nil(t, resp.Msg.Task)
+
+		// verify CleanupEphemeralRunners does not remove this runner
+		err = actions_service.CleanupEphemeralRunners(t.Context())
+		assert.NoError(t, err)
+
+		runner.client.runnerServiceClient.UpdateTask(t.Context(), connect.NewRequest(&runnerv1.UpdateTaskRequest{
+			State: &runnerv1.TaskState{
+				Id:     actionTask.ID,
+				Result: runnerv1.Result_RESULT_SUCCESS,
+			},
+		}))
+		resp, err = runner.client.runnerServiceClient.FetchTask(t.Context(), connect.NewRequest(&runnerv1.FetchTaskRequest{
+			TasksVersion: 0,
+		}))
+		assert.Error(t, err)
+		assert.Nil(t, resp)
+
+		resp, err = runner.client.runnerServiceClient.FetchTask(t.Context(), connect.NewRequest(&runnerv1.FetchTaskRequest{
+			TasksVersion: 0,
+		}))
+		assert.Error(t, err)
+		assert.Nil(t, resp)
+
+		// create an runner that picks a job and get force cancelled
+		runnerToBeRemoved := newMockRunner()
+		runnerToBeRemoved.registerAsRepoRunner(t, baseRepo.OwnerName, baseRepo.Name, "mock-runner-to-be-removed", []string{"ubuntu-latest"}, true)
+
+		taskToStopAPIObj := runnerToBeRemoved.fetchTask(t)
+
+		taskToStop := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionTask{ID: taskToStopAPIObj.Id})
+
+		// verify CleanupEphemeralRunners does not remove the custom crafted runner
+		err = actions_service.CleanupEphemeralRunners(t.Context())
+		assert.NoError(t, err)
+
+		runnerToRemove := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRunner{ID: taskToStop.RunnerID})
+
+		err = actions_model.StopTask(t.Context(), taskToStop.ID, actions_model.StatusFailure)
+		assert.NoError(t, err)
+
+		// verify CleanupEphemeralRunners does remove the custom crafted runner
+		err = actions_service.CleanupEphemeralRunners(t.Context())
+		assert.NoError(t, err)
+
+		unittest.AssertNotExistsBean(t, &actions_model.ActionRunner{ID: runnerToRemove.ID})
+
+		// this cleanup is required to allow further tests to pass
+		doAPIDeleteRepository(user2APICtx)(t)
+	})
+}
+
 func createActionsTestRepo(t *testing.T, authToken, repoName string, isPrivate bool) *api.Repository {
 	req := NewRequestWithJSON(t, "POST", "/api/v1/user/repos", &api.CreateRepoOption{
 		Name:          repoName,

tests/integration/actions_log_test.go

@@ -105,7 +105,7 @@ jobs:
 		apiRepo := createActionsTestRepo(t, token, "actions-download-task-logs", false)
 		repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: apiRepo.ID})
 		runner := newMockRunner()
-		runner.registerAsRepoRunner(t, user2.Name, repo.Name, "mock-runner", []string{"ubuntu-latest"})
+		runner.registerAsRepoRunner(t, user2.Name, repo.Name, "mock-runner", []string{"ubuntu-latest"}, false)
 
 		for _, tc := range testCases {
 			t.Run(fmt.Sprintf("test %s", tc.treePath), func(t *testing.T) {

tests/integration/actions_runner_test.go

@@ -67,19 +67,20 @@ func (r *mockRunner) doPing(t *testing.T) {
 	assert.Equal(t, "Hello, mock-runner!", resp.Msg.Data)
 }
 
-func (r *mockRunner) doRegister(t *testing.T, name, token string, labels []string) {
+func (r *mockRunner) doRegister(t *testing.T, name, token string, labels []string, ephemeral bool) {
 	r.doPing(t)
 	resp, err := r.client.runnerServiceClient.Register(t.Context(), connect.NewRequest(&runnerv1.RegisterRequest{
-		Name:    name,
-		Token:   token,
-		Version: "mock-runner-version",
-		Labels:  labels,
+		Name:      name,
+		Token:     token,
+		Version:   "mock-runner-version",
+		Labels:    labels,
+		Ephemeral: ephemeral,
 	}))
 	assert.NoError(t, err)
 	r.client = newMockRunnerClient(resp.Msg.Runner.Uuid, resp.Msg.Runner.Token)
 }
 
-func (r *mockRunner) registerAsRepoRunner(t *testing.T, ownerName, repoName, runnerName string, labels []string) {
+func (r *mockRunner) registerAsRepoRunner(t *testing.T, ownerName, repoName, runnerName string, labels []string, ephemeral bool) {
 	session := loginUser(t, ownerName)
 	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteRepository)
 	req := NewRequest(t, "GET", fmt.Sprintf("/api/v1/repos/%s/%s/actions/runners/registration-token", ownerName, repoName)).AddTokenAuth(token)
@@ -88,7 +89,7 @@ func (r *mockRunner) registerAsRepoRunner(t *testing.T, ownerName, repoName, run
 		Token string `json:"token"`
 	}
 	DecodeJSON(t, resp, &registrationToken)
-	r.doRegister(t, runnerName, registrationToken.Token, labels)
+	r.doRegister(t, runnerName, registrationToken.Token, labels, ephemeral)
 }
 
 func (r *mockRunner) fetchTask(t *testing.T, timeout ...time.Duration) *runnerv1.Task {

tests/integration/repo_webhook_test.go

@@ -639,7 +639,7 @@ func Test_WebhookWorkflowJob(t *testing.T) {
 		assert.NoError(t, err)
 
 		runner := newMockRunner()
-		runner.registerAsRepoRunner(t, "user2", "repo1", "mock-runner", []string{"ubuntu-latest"})
+		runner.registerAsRepoRunner(t, "user2", "repo1", "mock-runner", []string{"ubuntu-latest"}, false)
 
 		// 2. trigger the webhooks