cmd/flamenco-manager/main.go

@@ -27,6 +27,7 @@ import (
 	"projects.blender.org/studio/flamenco/internal/manager/api_impl/dummy"
 	"projects.blender.org/studio/flamenco/internal/manager/config"
 	"projects.blender.org/studio/flamenco/internal/manager/eventbus"
+	"projects.blender.org/studio/flamenco/internal/manager/farmstatus"
 	"projects.blender.org/studio/flamenco/internal/manager/job_compilers"
 	"projects.blender.org/studio/flamenco/internal/manager/job_deleter"
 	"projects.blender.org/studio/flamenco/internal/manager/last_rendered"
@@ -174,10 +175,12 @@ func runFlamencoManager() bool {
 	shamanServer := buildShamanServer(configService, isFirstRun)
 	jobDeleter := job_deleter.NewService(persist, localStorage, eventBroker, shamanServer)
 
+	farmStatus := farmstatus.NewService(persist)
+
 	flamenco := api_impl.NewFlamenco(
 		compiler, persist, eventBroker, logStorage, configService,
 		taskStateMachine, shamanServer, timeService, lastRender,
-		localStorage, sleepScheduler, jobDeleter)
+		localStorage, sleepScheduler, jobDeleter, farmStatus)
 
 	e := buildWebService(flamenco, persist, ssdp, socketio, urls, localStorage)
 
@@ -278,6 +281,13 @@ func runFlamencoManager() bool {
 		jobDeleter.Run(mainCtx)
 	}()
 
+	// Run the Farm Status service.
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		farmStatus.Run(mainCtx)
+	}()
+
 	// Log the URLs last, hopefully that makes them more visible / encouraging to go to for users.
 	go func() {
 		time.Sleep(100 * time.Millisecond)

internal/manager/api_impl/api_impl.go

@@ -28,6 +28,7 @@ type Flamenco struct {
 	localStorage   LocalStorage
 	sleepScheduler WorkerSleepScheduler
 	jobDeleter     JobDeleter
+	farmstatus     FarmStatusService
 
 	// The task scheduler can be locked to prevent multiple Workers from getting
 	// the same task. It is also used for certain other queries, like
@@ -55,6 +56,7 @@ func NewFlamenco(
 	localStorage LocalStorage,
 	wss WorkerSleepScheduler,
 	jd JobDeleter,
+	farmstatus FarmStatusService,
 ) *Flamenco {
 	return &Flamenco{
 		jobCompiler:    jc,
@@ -69,6 +71,7 @@ func NewFlamenco(
 		localStorage:   localStorage,
 		sleepScheduler: wss,
 		jobDeleter:     jd,
+		farmstatus:     farmstatus,
 
 		done: make(chan struct{}),
 	}

internal/manager/api_impl/interfaces.go

@@ -15,6 +15,7 @@ import (
 
 	"projects.blender.org/studio/flamenco/internal/manager/config"
 	"projects.blender.org/studio/flamenco/internal/manager/eventbus"
+	"projects.blender.org/studio/flamenco/internal/manager/farmstatus"
 	"projects.blender.org/studio/flamenco/internal/manager/job_compilers"
 	"projects.blender.org/studio/flamenco/internal/manager/job_deleter"
 	"projects.blender.org/studio/flamenco/internal/manager/last_rendered"
@@ -26,7 +27,7 @@ import (
 )
 
 // Generate mock implementations of these interfaces.
-//go:generate go run github.com/golang/mock/mockgen -destination mocks/api_impl_mock.gen.go -package mocks projects.blender.org/studio/flamenco/internal/manager/api_impl PersistenceService,ChangeBroadcaster,JobCompiler,LogStorage,ConfigService,TaskStateMachine,Shaman,LastRendered,LocalStorage,WorkerSleepScheduler,JobDeleter
+//go:generate go run github.com/golang/mock/mockgen -destination mocks/api_impl_mock.gen.go -package mocks projects.blender.org/studio/flamenco/internal/manager/api_impl PersistenceService,ChangeBroadcaster,JobCompiler,LogStorage,ConfigService,TaskStateMachine,Shaman,LastRendered,LocalStorage,WorkerSleepScheduler,JobDeleter,FarmStatusService
 
 type PersistenceService interface {
 	StoreAuthoredJob(ctx context.Context, authoredJob job_compilers.AuthoredJob) error
@@ -239,3 +240,9 @@ type JobDeleter interface {
 }
 
 var _ JobDeleter = (*job_deleter.Service)(nil)
+
+type FarmStatusService interface {
+	Report() api.FarmStatusReport
+}
+
+var _ FarmStatusService = (*farmstatus.Service)(nil)

internal/manager/api_impl/meta.go

@@ -321,6 +321,10 @@ func (f *Flamenco) SaveSetupAssistantConfig(e echo.Context) error {
 	return e.NoContent(http.StatusNoContent)
 }
 
+func (f *Flamenco) GetFarmStatus(e echo.Context) error {
+	return e.JSON(http.StatusOK, f.farmstatus.Report())
+}
+
 func flamencoManagerDir() (string, error) {
 	exename, err := os.Executable()
 	if err != nil {

internal/manager/api_impl/mocks/api_impl_mock.gen.go

@@ -1,5 +1,5 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: projects.blender.org/studio/flamenco/internal/manager/api_impl (interfaces: PersistenceService,ChangeBroadcaster,JobCompiler,LogStorage,ConfigService,TaskStateMachine,Shaman,LastRendered,LocalStorage,WorkerSleepScheduler,JobDeleter)
+// Source: projects.blender.org/studio/flamenco/internal/manager/api_impl (interfaces: PersistenceService,ChangeBroadcaster,JobCompiler,LogStorage,ConfigService,TaskStateMachine,Shaman,LastRendered,LocalStorage,WorkerSleepScheduler,JobDeleter,FarmStatusService)
 
 // Package mocks is a generated GoMock package.
 package mocks
@@ -1413,3 +1413,40 @@ func (mr *MockJobDeleterMockRecorder) WhatWouldBeDeleted(arg0 interface{}) *gomo
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WhatWouldBeDeleted", reflect.TypeOf((*MockJobDeleter)(nil).WhatWouldBeDeleted), arg0)
 }
+
+// MockFarmStatusService is a mock of FarmStatusService interface.
+type MockFarmStatusService struct {
+	ctrl     *gomock.Controller
+	recorder *MockFarmStatusServiceMockRecorder
+}
+
+// MockFarmStatusServiceMockRecorder is the mock recorder for MockFarmStatusService.
+type MockFarmStatusServiceMockRecorder struct {
+	mock *MockFarmStatusService
+}
+
+// NewMockFarmStatusService creates a new mock instance.
+func NewMockFarmStatusService(ctrl *gomock.Controller) *MockFarmStatusService {
+	mock := &MockFarmStatusService{ctrl: ctrl}
+	mock.recorder = &MockFarmStatusServiceMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockFarmStatusService) EXPECT() *MockFarmStatusServiceMockRecorder {
+	return m.recorder
+}
+
+// Report mocks base method.
+func (m *MockFarmStatusService) Report() api.FarmStatusReport {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Report")
+	ret0, _ := ret[0].(api.FarmStatusReport)
+	return ret0
+}
+
+// Report indicates an expected call of Report.
+func (mr *MockFarmStatusServiceMockRecorder) Report() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Report", reflect.TypeOf((*MockFarmStatusService)(nil).Report))
+}

internal/manager/api_impl/support_test.go

@@ -37,6 +37,7 @@ type mockedFlamenco struct {
 	localStorage   *mocks.MockLocalStorage
 	sleepScheduler *mocks.MockWorkerSleepScheduler
 	jobDeleter     *mocks.MockJobDeleter
+	farmstatus     *mocks.MockFarmStatusService
 
 	// Place for some tests to store a temporary directory.
 	tempdir string
@@ -54,6 +55,7 @@ func newMockedFlamenco(mockCtrl *gomock.Controller) mockedFlamenco {
 	localStore := mocks.NewMockLocalStorage(mockCtrl)
 	wss := mocks.NewMockWorkerSleepScheduler(mockCtrl)
 	jd := mocks.NewMockJobDeleter(mockCtrl)
+	fs := mocks.NewMockFarmStatusService(mockCtrl)
 
 	clock := clock.NewMock()
 	mockedNow, err := time.Parse(time.RFC3339, "2022-06-09T11:14:41+02:00")
@@ -62,7 +64,7 @@ func newMockedFlamenco(mockCtrl *gomock.Controller) mockedFlamenco {
 	}
 	clock.Set(mockedNow)
 
-	f := NewFlamenco(jc, ps, cb, logStore, cs, sm, sha, clock, lr, localStore, wss, jd)
+	f := NewFlamenco(jc, ps, cb, logStore, cs, sm, sha, clock, lr, localStore, wss, jd, fs)
 
 	return mockedFlamenco{
 		flamenco:       f,
@@ -78,6 +80,7 @@ func newMockedFlamenco(mockCtrl *gomock.Controller) mockedFlamenco {
 		localStorage:   localStore,
 		sleepScheduler: wss,
 		jobDeleter:     jd,
+		farmstatus:     fs,
 	}
 }
 

internal/manager/farmstatus/farmstatus.go

@@ -0,0 +1,169 @@
+// package farmstatus provides a status indicator for the entire Flamenco farm.
+package farmstatus
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"sync"
+	"time"
+
+	"github.com/rs/zerolog/log"
+	"projects.blender.org/studio/flamenco/pkg/api"
+	"projects.blender.org/studio/flamenco/pkg/website"
+)
+
+const (
+	// pollWait determines how often the persistence layer is queried to get the
+	// counts & statuses of workers and jobs.
+	//
+	// Note that this indicates the time between polls, so between a poll
+	// operation being done, and the next one starting.
+	pollWait = 5 * time.Second
+)
+
+// Service keeps track of the overall farm status.
+type Service struct {
+	persist PersistenceService
+
+	mutex      sync.Mutex
+	lastReport api.FarmStatusReport
+}
+
+func NewService(persist PersistenceService) *Service {
+	return &Service{
+		persist: persist,
+		mutex:   sync.Mutex{},
+		lastReport: api.FarmStatusReport{
+			Status: api.FarmStatusStarting,
+		},
+	}
+}
+
+// Run the farm status polling loop.
+func (s *Service) Run(ctx context.Context) {
+	log.Debug().Msg("farm status: polling service running")
+	defer log.Debug().Msg("farm status: polling service stopped")
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(pollWait):
+			s.poll(ctx)
+		}
+	}
+}
+
+// Report returns the last-known farm status report.
+//
+// It is updated every few seconds, from the Run() function.
+func (s *Service) Report() api.FarmStatusReport {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.lastReport
+}
+
+func (s *Service) poll(ctx context.Context) {
+	report := s.checkFarmStatus(ctx)
+	if report == nil {
+		// Already logged, just keep the last known log around for querying.
+		return
+	}
+
+	s.mutex.Lock()
+	s.lastReport = *report
+	s.mutex.Unlock()
+}
+
+// checkFarmStatus checks the farm status by querying the peristence layer.
+// This function does not return an error, but instead logs them as warnings and returns nil.
+func (s *Service) checkFarmStatus(ctx context.Context) *api.FarmStatusReport {
+	log.Trace().Msg("farm status: checking the farm status")
+	startTime := time.Now()
+
+	defer func() {
+		duration := time.Since(startTime)
+		log.Debug().Stringer("duration", duration).Msg("farm status: checked the farm status")
+	}()
+
+	workerStatuses, err := s.persist.SummarizeWorkerStatuses(ctx)
+	if err != nil {
+		logDBError(err, "farm status: could not summarize worker statuses")
+		return nil
+	}
+
+	// Check some worker statuses first. When there are no workers and the farm is
+	// inoperative, there is little use in checking jobs. At least for now. Maybe
+	// later we want to have some info in the reported status that indicates a
+	// more pressing matter (as in, inoperative AND a job is queued).
+
+	// Check: inoperative
+	if len(workerStatuses) == 0 || allIn(workerStatuses, api.WorkerStatusOffline, api.WorkerStatusError) {
+		return &api.FarmStatusReport{
+			Status: api.FarmStatusInoperative,
+		}
+	}
+
+	jobStatuses, err := s.persist.SummarizeJobStatuses(ctx)
+	if err != nil {
+		logDBError(err, "farm status: could not summarize job statuses")
+		return nil
+	}
+
+	anyJobActive := jobStatuses[api.JobStatusActive] > 0
+	anyJobQueued := jobStatuses[api.JobStatusQueued] > 0
+	isWorkAvailable := anyJobActive || anyJobQueued
+
+	anyWorkerAwake := workerStatuses[api.WorkerStatusAwake] > 0
+	anyWorkerAsleep := workerStatuses[api.WorkerStatusAsleep] > 0
+	allWorkersAsleep := !anyWorkerAwake && anyWorkerAsleep
+
+	report := api.FarmStatusReport{}
+	switch {
+	case anyJobActive && anyWorkerAwake:
+		// - "active" # Actively working on jobs.
+		report.Status = api.FarmStatusActive
+	case isWorkAvailable:
+		// - "waiting" # Work to be done, but there is no worker awake.
+		report.Status = api.FarmStatusWaiting
+	case !isWorkAvailable && allWorkersAsleep:
+		// - "asleep" # Farm is idle, and all workers are asleep.
+		report.Status = api.FarmStatusAsleep
+	case !isWorkAvailable:
+		// - "idle" # Farm could be active, but has no work to do.
+		report.Status = api.FarmStatusIdle
+	default:
+		log.Warn().
+			Interface("workerStatuses", workerStatuses).
+			Interface("jobStatuses", jobStatuses).
+			Msgf("farm status: unexpected configuration of worker and job statuses, please report this at %s", website.BugReportURL)
+		report.Status = api.FarmStatusUnknown
+	}
+
+	return &report
+}
+
+func logDBError(err error, message string) {
+	switch {
+	case errors.Is(err, context.DeadlineExceeded):
+		log.Warn().Msg(message + " (it took too long)")
+	case errors.Is(err, context.Canceled):
+		log.Debug().Msg(message + " (Flamenco is shutting down)")
+	default:
+		log.Warn().AnErr("cause", err).Msg(message)
+	}
+}
+
+func allIn[T comparable](statuses map[T]int, shouldBeIn ...T) bool {
+	for status, count := range statuses {
+		if count == 0 {
+			continue
+		}
+
+		if !slices.Contains(shouldBeIn, status) {
+			return false
+		}
+	}
+	return true
+}

internal/manager/farmstatus/farmstatus_test.go

@@ -0,0 +1,213 @@
+// package farmstatus provides a status indicator for the entire Flamenco farm.
+package farmstatus
+
+import (
+	"context"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"projects.blender.org/studio/flamenco/internal/manager/farmstatus/mocks"
+	"projects.blender.org/studio/flamenco/internal/manager/persistence"
+	"projects.blender.org/studio/flamenco/pkg/api"
+)
+
+type Fixtures struct {
+	service *Service
+	persist *mocks.MockPersistenceService
+	ctx     context.Context
+}
+
+func TestFarmStatusStarting(t *testing.T) {
+	f := fixtures(t)
+	report := f.service.Report()
+	assert.Equal(t, api.FarmStatusStarting, report.Status)
+}
+
+func TestFarmStatusLoop(t *testing.T) {
+	f := fixtures(t)
+
+	// Mock an "active" status.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 2,
+		api.WorkerStatusAsleep:  1,
+		api.WorkerStatusError:   1,
+		api.WorkerStatusAwake:   3,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusActive: 1,
+	})
+
+	// Before polling, the status should still be 'starting'.
+	report := f.service.Report()
+	assert.Equal(t, api.FarmStatusStarting, report.Status)
+
+	// After a single poll, the report should have been updated.
+	f.service.poll(f.ctx)
+	report = f.service.Report()
+	assert.Equal(t, api.FarmStatusActive, report.Status)
+}
+
+func TestCheckFarmStatusInoperative(t *testing.T) {
+	f := fixtures(t)
+
+	// "inoperative": no workers.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{})
+	report := f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusInoperative, report.Status)
+
+	// "inoperative": all workers offline.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 3,
+	})
+	report = f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusInoperative, report.Status)
+
+	// "inoperative": some workers offline, some in error,
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 2,
+		api.WorkerStatusError:   1,
+	})
+	report = f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusInoperative, report.Status)
+}
+
+func TestCheckFarmStatusActive(t *testing.T) {
+	f := fixtures(t)
+
+	// "active" # Actively working on jobs.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 2,
+		api.WorkerStatusAsleep:  1,
+		api.WorkerStatusError:   1,
+		api.WorkerStatusAwake:   3,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusActive: 1,
+	})
+	report := f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusActive, report.Status)
+}
+
+func TestCheckFarmStatusWaiting(t *testing.T) {
+	f := fixtures(t)
+
+	// "waiting": Active job, and only sleeping workers.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusAsleep: 1,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusActive: 1,
+	})
+	report := f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusWaiting, report.Status)
+
+	// "waiting": Queued job, and awake worker. It could pick up the job any
+	// second now, but it could also have been blocklisted already.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusAsleep: 1,
+		api.WorkerStatusAwake:  1,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusQueued: 1,
+	})
+	report = f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusWaiting, report.Status)
+}
+
+func TestCheckFarmStatusIdle(t *testing.T) {
+	f := fixtures(t)
+
+	// "idle" # Farm could be active, but has no work to do.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 2,
+		api.WorkerStatusAsleep:  1,
+		api.WorkerStatusAwake:   1,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusCompleted:       1,
+		api.JobStatusCancelRequested: 1,
+	})
+	report := f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusIdle, report.Status)
+}
+
+func TestCheckFarmStatusAsleep(t *testing.T) {
+	f := fixtures(t)
+
+	// "asleep": No worker is awake, some are asleep, no work to do.
+	f.mockWorkerStatuses(persistence.WorkerStatusCount{
+		api.WorkerStatusOffline: 2,
+		api.WorkerStatusAsleep:  2,
+	})
+	f.mockJobStatuses(persistence.JobStatusCount{
+		api.JobStatusCanceled:  10,
+		api.JobStatusCompleted: 4,
+		api.JobStatusFailed:    2,
+	})
+	report := f.service.checkFarmStatus(f.ctx)
+	require.NotNil(t, report)
+	assert.Equal(t, api.FarmStatusAsleep, report.Status)
+}
+
+func Test_allIn(t *testing.T) {
+	type args struct {
+		statuses   map[api.WorkerStatus]int
+		shouldBeIn []api.WorkerStatus
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{"none", args{map[api.WorkerStatus]int{}, []api.WorkerStatus{api.WorkerStatusAsleep}}, true},
+		{"match-only", args{
+			map[api.WorkerStatus]int{api.WorkerStatusAsleep: 5},
+			[]api.WorkerStatus{api.WorkerStatusAsleep},
+		}, true},
+		{"match-some", args{
+			map[api.WorkerStatus]int{api.WorkerStatusAsleep: 5, api.WorkerStatusOffline: 2},
+			[]api.WorkerStatus{api.WorkerStatusAsleep},
+		}, false},
+		{"match-all", args{
+			map[api.WorkerStatus]int{api.WorkerStatusAsleep: 5, api.WorkerStatusOffline: 2},
+			[]api.WorkerStatus{api.WorkerStatusAsleep, api.WorkerStatusOffline},
+		}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := allIn(tt.args.statuses, tt.args.shouldBeIn...); got != tt.want {
+				t.Errorf("allIn() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func fixtures(t *testing.T) *Fixtures {
+	mockCtrl := gomock.NewController(t)
+
+	f := Fixtures{
+		persist: mocks.NewMockPersistenceService(mockCtrl),
+		ctx:     context.Background(),
+	}
+
+	f.service = NewService(f.persist)
+
+	return &f
+}
+
+func (f *Fixtures) mockWorkerStatuses(workerStatuses persistence.WorkerStatusCount) {
+	f.persist.EXPECT().SummarizeWorkerStatuses(f.ctx).Return(workerStatuses, nil)
+}
+
+func (f *Fixtures) mockJobStatuses(jobStatuses persistence.JobStatusCount) {
+	f.persist.EXPECT().SummarizeJobStatuses(f.ctx).Return(jobStatuses, nil)
+}

internal/manager/farmstatus/interfaces.go

@@ -0,0 +1,17 @@
+package farmstatus
+
+import (
+	"context"
+
+	"projects.blender.org/studio/flamenco/internal/manager/persistence"
+)
+
+// Generate mock implementations of these interfaces.
+//go:generate go run github.com/golang/mock/mockgen -destination mocks/interfaces_mock.gen.go -package mocks projects.blender.org/studio/flamenco/internal/manager/farmstatus PersistenceService
+
+type PersistenceService interface {
+	SummarizeJobStatuses(ctx context.Context) (persistence.JobStatusCount, error)
+	SummarizeWorkerStatuses(ctx context.Context) (persistence.WorkerStatusCount, error)
+}
+
+var _ PersistenceService = (*persistence.DB)(nil)

internal/manager/farmstatus/mocks/interfaces_mock.gen.go

@@ -0,0 +1,66 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: projects.blender.org/studio/flamenco/internal/manager/farmstatus (interfaces: PersistenceService)
+
+// Package mocks is a generated GoMock package.
+package mocks
+
+import (
+	context "context"
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+	persistence "projects.blender.org/studio/flamenco/internal/manager/persistence"
+)
+
+// MockPersistenceService is a mock of PersistenceService interface.
+type MockPersistenceService struct {
+	ctrl     *gomock.Controller
+	recorder *MockPersistenceServiceMockRecorder
+}
+
+// MockPersistenceServiceMockRecorder is the mock recorder for MockPersistenceService.
+type MockPersistenceServiceMockRecorder struct {
+	mock *MockPersistenceService
+}
+
+// NewMockPersistenceService creates a new mock instance.
+func NewMockPersistenceService(ctrl *gomock.Controller) *MockPersistenceService {
+	mock := &MockPersistenceService{ctrl: ctrl}
+	mock.recorder = &MockPersistenceServiceMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockPersistenceService) EXPECT() *MockPersistenceServiceMockRecorder {
+	return m.recorder
+}
+
+// SummarizeJobStatuses mocks base method.
+func (m *MockPersistenceService) SummarizeJobStatuses(arg0 context.Context) (persistence.JobStatusCount, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "SummarizeJobStatuses", arg0)
+	ret0, _ := ret[0].(persistence.JobStatusCount)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// SummarizeJobStatuses indicates an expected call of SummarizeJobStatuses.
+func (mr *MockPersistenceServiceMockRecorder) SummarizeJobStatuses(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SummarizeJobStatuses", reflect.TypeOf((*MockPersistenceService)(nil).SummarizeJobStatuses), arg0)
+}
+
+// SummarizeWorkerStatuses mocks base method.
+func (m *MockPersistenceService) SummarizeWorkerStatuses(arg0 context.Context) (persistence.WorkerStatusCount, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "SummarizeWorkerStatuses", arg0)
+	ret0, _ := ret[0].(persistence.WorkerStatusCount)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// SummarizeWorkerStatuses indicates an expected call of SummarizeWorkerStatuses.
+func (mr *MockPersistenceServiceMockRecorder) SummarizeWorkerStatuses(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SummarizeWorkerStatuses", reflect.TypeOf((*MockPersistenceService)(nil).SummarizeWorkerStatuses), arg0)
+}

internal/manager/persistence/jobs_query.go

@@ -86,3 +86,33 @@ func (db *DB) QueryJobTaskSummaries(ctx context.Context, jobUUID string) ([]*Tas
 
 	return result, tx.Error
 }
+
+// JobStatusCount is a mapping from job status to the number of jobs in that status.
+type JobStatusCount map[api.JobStatus]int
+
+func (db *DB) SummarizeJobStatuses(ctx context.Context) (JobStatusCount, error) {
+	logger := log.Ctx(ctx)
+	logger.Debug().Msg("database: summarizing job statuses")
+
+	// Query the database using a data structure that's easy to handle in GORM.
+	type queryResult struct {
+		Status      api.JobStatus
+		StatusCount int
+	}
+	result := []*queryResult{}
+	tx := db.gormDB.WithContext(ctx).Model(&Job{}).
+		Select("status as Status", "count(id) as StatusCount").
+		Group("status").
+		Scan(&result)
+	if tx.Error != nil {
+		return nil, jobError(tx.Error, "summarizing job statuses")
+	}
+
+	// Convert the array-of-structs to a map that's easier to handle by the caller.
+	statusCounts := make(JobStatusCount)
+	for _, singleStatusCount := range result {
+		statusCounts[singleStatusCount.Status] = singleStatusCount.StatusCount
+	}
+
+	return statusCounts, nil
+}

internal/manager/persistence/jobs_query_test.go

@@ -4,9 +4,12 @@ package persistence
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 import (
+	"context"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"projects.blender.org/studio/flamenco/internal/manager/job_compilers"
 	"projects.blender.org/studio/flamenco/internal/uuid"
@@ -141,3 +144,58 @@ func TestQueryJobTaskSummaries(t *testing.T) {
 		assert.True(t, expectTaskUUIDs[summary.UUID], "%q should be in %v", summary.UUID, expectTaskUUIDs)
 	}
 }
+
+func TestSummarizeJobStatuses(t *testing.T) {
+	ctx, close, db, job1, authoredJob1 := jobTasksTestFixtures(t)
+	defer close()
+
+	// Create another job
+	authoredJob2 := duplicateJobAndTasks(authoredJob1)
+	job2 := persistAuthoredJob(t, ctx, db, authoredJob2)
+
+	// Test the summary.
+	summary, err := db.SummarizeJobStatuses(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, JobStatusCount{api.JobStatusUnderConstruction: 2}, summary)
+
+	// Change the jobs so that each has a unique status.
+	job1.Status = api.JobStatusQueued
+	require.NoError(t, db.SaveJobStatus(ctx, job1))
+	job2.Status = api.JobStatusFailed
+	require.NoError(t, db.SaveJobStatus(ctx, job2))
+
+	// Test the summary.
+	summary, err = db.SummarizeJobStatuses(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, JobStatusCount{
+		api.JobStatusQueued: 1,
+		api.JobStatusFailed: 1,
+	}, summary)
+
+	// Delete all jobs.
+	require.NoError(t, db.DeleteJob(ctx, job1.UUID))
+	require.NoError(t, db.DeleteJob(ctx, job2.UUID))
+
+	// Test the summary.
+	summary, err = db.SummarizeJobStatuses(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, JobStatusCount{}, summary)
+}
+
+// Check that a context timeout can be detected by inspecting the
+// returned error.
+func TestSummarizeJobStatusesTimeout(t *testing.T) {
+	ctx, close, db, _, _ := jobTasksTestFixtures(t)
+	defer close()
+
+	subCtx, subCtxCancel := context.WithTimeout(ctx, 1*time.Nanosecond)
+	defer subCtxCancel()
+
+	// Force a timeout of the context. And yes, even when a nanosecond is quite
+	// short, it is still necessary to wait.
+	time.Sleep(2 * time.Nanosecond)
+
+	summary, err := db.SummarizeJobStatuses(subCtx)
+	assert.ErrorIs(t, err, context.DeadlineExceeded)
+	assert.Nil(t, summary)
+}

internal/manager/persistence/workers.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/rs/zerolog/log"
 	"gorm.io/gorm"
 	"projects.blender.org/studio/flamenco/pkg/api"
 )
@@ -176,3 +177,33 @@ func (db *DB) WorkerSeen(ctx context.Context, w *Worker) error {
 	}
 	return nil
 }
+
+// WorkerStatusCount is a mapping from job status to the number of jobs in that status.
+type WorkerStatusCount map[api.WorkerStatus]int
+
+func (db *DB) SummarizeWorkerStatuses(ctx context.Context) (WorkerStatusCount, error) {
+	logger := log.Ctx(ctx)
+	logger.Debug().Msg("database: summarizing worker statuses")
+
+	// Query the database using a data structure that's easy to handle in GORM.
+	type queryResult struct {
+		Status      api.WorkerStatus
+		StatusCount int
+	}
+	result := []*queryResult{}
+	tx := db.gormDB.WithContext(ctx).Model(&Worker{}).
+		Select("status as Status", "count(id) as StatusCount").
+		Group("status").
+		Scan(&result)
+	if tx.Error != nil {
+		return nil, workerError(tx.Error, "summarizing worker statuses")
+	}
+
+	// Convert the array-of-structs to a map that's easier to handle by the caller.
+	statusCounts := make(WorkerStatusCount)
+	for _, singleStatusCount := range result {
+		statusCounts[singleStatusCount.Status] = singleStatusCount.StatusCount
+	}
+
+	return statusCounts, nil
+}

internal/manager/persistence/workers_test.go

@@ -4,6 +4,7 @@ package persistence
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 import (
+	"context"
 	"testing"
 	"time"
 
@@ -334,3 +335,65 @@ func TestDeleteWorkerWithTagAssigned(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, tag.Workers)
 }
+
+func TestSummarizeWorkerStatuses(t *testing.T) {
+	f := workerTestFixtures(t, 1*time.Second)
+	defer f.done()
+
+	// Test the summary.
+	summary, err := f.db.SummarizeWorkerStatuses(f.ctx)
+	require.NoError(t, err)
+	assert.Equal(t, WorkerStatusCount{api.WorkerStatusAwake: 1}, summary)
+
+	// Create more workers.
+	w1 := Worker{
+		UUID:   "fd97a35b-a5bd-44b4-ac2b-64c193ca877d",
+		Name:   "Worker 1",
+		Status: api.WorkerStatusAwake,
+	}
+	w2 := Worker{
+		UUID:   "82b2d176-cb8c-4bfa-8300-41c216d766df",
+		Name:   "Worker  2",
+		Status: api.WorkerStatusOffline,
+	}
+
+	require.NoError(t, f.db.CreateWorker(f.ctx, &w1))
+	require.NoError(t, f.db.CreateWorker(f.ctx, &w2))
+
+	// Test the summary.
+	summary, err = f.db.SummarizeWorkerStatuses(f.ctx)
+	require.NoError(t, err)
+	assert.Equal(t, WorkerStatusCount{
+		api.WorkerStatusAwake:   2,
+		api.WorkerStatusOffline: 1,
+	}, summary)
+
+	// Delete all workers.
+	require.NoError(t, f.db.DeleteWorker(f.ctx, f.worker.UUID))
+	require.NoError(t, f.db.DeleteWorker(f.ctx, w1.UUID))
+	require.NoError(t, f.db.DeleteWorker(f.ctx, w2.UUID))
+
+	// Test the summary.
+	summary, err = f.db.SummarizeWorkerStatuses(f.ctx)
+	require.NoError(t, err)
+	assert.Equal(t, WorkerStatusCount{}, summary)
+}
+
+// Check that a context timeout can be detected by inspecting the
+// returned error.
+func TestSummarizeWorkerStatusesTimeout(t *testing.T) {
+	f := workerTestFixtures(t, 1*time.Second)
+	defer f.done()
+
+	subCtx, subCtxCancel := context.WithTimeout(f.ctx, 1*time.Nanosecond)
+	defer subCtxCancel()
+
+	// Force a timeout of the context. And yes, even when a nanosecond is quite
+	// short, it is still necessary to wait.
+	time.Sleep(2 * time.Nanosecond)
+
+	// Test the summary.
+	summary, err := f.db.SummarizeWorkerStatuses(subCtx)
+	assert.ErrorIs(t, err, context.DeadlineExceeded)
+	assert.Nil(t, summary)
+}