fix(master): redirect a cancelled Check now instead of an empty response (#35)

CLAUDE.md

@@ -38,7 +38,7 @@ DATABASE_URL=postgres://... go test -tags integration ./internal/master/store/
 - `internal/master/hub`      — agent connections: auth, per-connection writer, routing, job reconcile on hello
 - `internal/master/registry` — HEAD-only digest lookup and tag listing against a registry (go-containerregistry, `DOCKER_CONFIG` credentials)
 - `internal/master/tagver`   — which tag is a newer version of a followed tag (pure functions)
-- `internal/master/poller`   — every `POLL_INTERVAL`: one lookup per followed `repo:tag`, sets the available version, starts auto jobs; one tag list per repo, sets the newer tag suggestion
+- `internal/master/poller`   — every `POLL_INTERVAL`: one lookup per followed `repo:tag`, sets the available version, starts auto jobs; one tag list per repo, sets the newer tag suggestion; `PollService` does the same for one service (UI Check now)
 - `internal/master/jobs`     — decides whether a service may be updated and starts a job on the right agent
 - `internal/master/webhook`  — `POST /update`: records the available version, starts jobs for auto services, waits for them
 - `internal/master/web/icons` — embedded Simple Icons path data; slug derived from the image ref; regenerate with `go generate ./internal/master/web/icons`

README.md

@@ -156,6 +156,9 @@ multi-arch image the digest is the index digest, the same one `docker inspect` s
 - **What is not polled.** Services that follow no tag (`repo@digest`), `build:` services, and
   services without a registry digest (locally built images). The service page says which.
   Plain containers are polled, so their badge works, but jobs for them are refused.
+- **Check now.** The service page's *Check now* button runs the same check immediately for that
+  service only (digest, auto job, newer tag); other services that follow the same tag are
+  updated at the next cycle.
 - **Errors.** A failed lookup is stored for the services that follow that tag and shown as a
   "poll failed" badge on the overview and in the "Polling" row of the service page; other
   tags continue. A later success clears it.

cmd/master/main.go

@@ -115,7 +115,17 @@ func run() error {
 	}
 	auth := webauth.New(provider, st, cfg.AllowedGroup, strings.HasPrefix(cfg.PublicURL, "https://"), logger)
 
-	ui, err := web.New(st, agentHub, jobService, broker, web.Config{
+	credDir, credFound, credReadErr := registryCredentialsDir()
+	logger.Info("registry_credentials", "docker_config", credDir, "config_json_found", credFound,
+		"config_json_readable", credFound && credReadErr == nil)
+	if credReadErr != nil {
+		logger.Warn("registry_credentials_unreadable", "docker_config", credDir, "error", credReadErr)
+	}
+	registryPoller := poller.New(st, jobService, registry.New("package-updater-master/"+version, logger), broker, poller.Config{
+		Interval: cfg.PollInterval, FirstDelay: pollFirstDelay, Workers: pollWorkers,
+	}, logger)
+
+	ui, err := web.New(st, agentHub, jobService, broker, registryPoller, web.Config{
 		AgentURL: cfg.AgentURL, MasterKey: fingerprint, AgentImage: cfg.AgentImage,
 		PollInterval: cfg.PollInterval, Version: version,
 	}, logger)
@@ -164,17 +174,8 @@ func run() error {
 		BaseContext: baseContext,
 	}
 
-	credDir, credFound, credReadErr := registryCredentialsDir()
-	logger.Info("registry_credentials", "docker_config", credDir, "config_json_found", credFound,
-		"config_json_readable", credFound && credReadErr == nil)
-	if credReadErr != nil {
-		logger.Warn("registry_credentials_unreadable", "docker_config", credDir, "error", credReadErr)
-	}
 	pollCtx, stopPolling := context.WithCancel(ctx)
 	defer stopPolling()
-	registryPoller := poller.New(st, jobService, registry.New("package-updater-master/"+version, logger), broker, poller.Config{
-		Interval: cfg.PollInterval, FirstDelay: pollFirstDelay, Workers: pollWorkers,
-	}, logger)
 	pollDone := make(chan struct{})
 	go func() {
 		defer close(pollDone)

internal/master/poller/poller.go

@@ -139,6 +139,17 @@ func (p *Poller) Cycle(ctx context.Context) {
 		p.log.Error("poll_list_failed", "error", err)
 		return
 	}
+	stats := p.pollServices(ctx, svcs)
+	p.log.Info("poll_cycle", "refs", stats.refs, "ok", stats.ok, "failed", stats.failed,
+		"suggested", stats.suggested, "jobs", stats.jobs, "skipped", stats.skipped,
+		"repos_listed", stats.reposListed, "tags_failed", stats.tagsFailed, "newer", stats.newer,
+		"duration_ms", p.now().Sub(began).Milliseconds())
+}
+
+// pollServices does the work of a cycle for svcs: it looks up every distinct
+// followed ref once, records the results and starts auto jobs, then syncs the
+// newer-tag suggestions of svcs.
+func (p *Poller) pollServices(ctx context.Context, svcs []model.Service) cycleStats {
 	var stats cycleStats
 	byRef := map[string][]model.Service{}
 	var refs []string
@@ -170,10 +181,41 @@ func (p *Poller) Cycle(ctx context.Context) {
 	p.publishIfWrote(&stats)
 	p.syncNewer(ctx, write, svcs, &stats)
 	p.publishIfWrote(&stats)
-	p.log.Info("poll_cycle", "refs", stats.refs, "ok", stats.ok, "failed", stats.failed,
-		"suggested", stats.suggested, "jobs", stats.jobs, "skipped", stats.skipped,
-		"repos_listed", stats.reposListed, "tags_failed", stats.tagsFailed, "newer", stats.newer,
+	return stats
+}
+
+// NotPolledError says a service cannot be checked against the registry.
+type NotPolledError struct{ Reason string }
+
+func (e *NotPolledError) Error() string { return "not polled: " + e.Reason }
+
+// PollService does what Cycle does, for the service id only: it looks up the
+// followed ref, records the digest, starts an auto job if one is wanted and
+// syncs the newer-tag suggestion. Other services that follow the same ref are
+// updated at the next cycle. It is safe to run while Run is running: the
+// unique index update_jobs_one_active prevents duplicate jobs. A registry
+// error is not returned; it is stored as last_poll_error, like in a cycle. It
+// returns the store's error when the service cannot be read, model.ErrNotFound
+// for a removed service, *NotPolledError when the service is not polled, and
+// ctx.Err() when ctx ended.
+func (p *Poller) PollService(ctx context.Context, id int64) error {
+	began := p.now()
+	svc, err := p.store.GetService(ctx, id)
+	if err != nil {
+		return err
+	}
+	if svc.RemovedAt != nil {
+		return model.ErrNotFound
+	}
+	if r := SkipReason(svc); r != "" {
+		return &NotPolledError{Reason: r}
+	}
+	stats := p.pollServices(ctx, []model.Service{svc})
+	p.log.Info("poll_service", "service_id", id, "ref", jobs.FollowedRef(svc.ActualRef),
+		"ok", stats.ok, "failed", stats.failed, "suggested", stats.suggested, "jobs", stats.jobs,
+		"tags_failed", stats.tagsFailed, "newer", stats.newer,
 		"duration_ms", p.now().Sub(began).Milliseconds())
+	return ctx.Err()
 }
 
 // publishIfWrote tells the browsers to refresh if a phase of the cycle wrote

internal/master/poller/poller_test.go

@@ -938,3 +938,160 @@ func TestDigestWritesArePublishedBeforeTagsAreListed(t *testing.T) {
 	close(reg.tagRelease)
 	<-done
 }
+
+func TestPollService(t *testing.T) {
+	ref := repoA + ":latest" // not version-like: no tag listing
+	newDigest := map[string]string{ref: "sha256:new"}
+	auto := func(edit func(*model.Service)) model.Service {
+		s := svc(1, ref)
+		s.UpdateMode = model.ModeAuto
+		if edit != nil {
+			edit(&s)
+		}
+		return s
+	}
+	tests := []struct {
+		name        string
+		svc         model.Service
+		reg         *fakeRegistry
+		startErr    error
+		wantErr     error // matched with ErrorIs
+		wantNotPoll string
+		wantHeads   []string
+		wantTags    []string
+		check       func(t *testing.T, st *fakeStore, j *fakeJobs)
+	}{
+		{name: "manual with a new digest is only marked",
+			svc: svc(1, ref), reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				require.Len(t, st.available, 1)
+				assert.Equal(t, model.SourcePoll, st.available[0].a.Source)
+				assert.Empty(t, j.starts)
+			}},
+		{name: "auto with a new digest starts a poll job",
+			svc: auto(nil), reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				assert.Equal(t, []startCall{{1, jobs.StartRequest{Trigger: model.TriggerPoll, Ref: ref}}}, j.starts)
+				assert.Equal(t, []lastTagCall{{1, "sha256:new"}}, st.lastTag)
+			}},
+		{name: "auto that cannot be updated is marked but last_tag_digest stays",
+			svc: auto(nil), reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			startErr: &model.NotUpdatableError{Reason: model.ReasonDrifted},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				assert.Len(t, st.available, 1)
+				assert.Len(t, j.starts, 1)
+				assert.Empty(t, st.lastTag)
+			}},
+		{name: "auto that already got the digest is not started",
+			svc: auto(func(s *model.Service) { s.LastTagDigest = "sha256:new" }),
+			reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) { assert.Empty(t, j.starts) }},
+		{name: "auto whose desired_ref names the digest is not started",
+			svc: auto(func(s *model.Service) { s.DesiredRef = ref + "@sha256:new" }),
+			reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) { assert.Empty(t, j.starts) }},
+		{name: "registry error is stored, not returned",
+			svc: svc(1, ref), reg: &fakeRegistry{errs: map[string]error{ref: errors.New("head: boom")}}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				assert.Equal(t, []pollErrorCall{{[]int64{1}, "head: boom"}}, st.pollErrors)
+			}},
+		{name: "a previous poll error is cleared on success",
+			svc: auto(func(s *model.Service) {
+				s.UpdateMode, s.ActualDigest, s.LastPollError = model.ModeManual, "sha256:new", "head: boom"
+			}),
+			reg: &fakeRegistry{digests: newDigest}, wantHeads: []string{ref},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				assert.Equal(t, []pollErrorCall{{[]int64{1}, ""}}, st.pollErrors)
+			}},
+		{name: "no tag is not polled",
+			svc: svc(1, repoA+"@sha256:old"), reg: &fakeRegistry{}, wantNotPoll: model.ReasonNoTag},
+		{name: "built is not polled",
+			svc: auto(func(s *model.Service) { s.Built = true }), reg: &fakeRegistry{}, wantNotPoll: "built from source"},
+		{name: "no digest is not polled",
+			svc: auto(func(s *model.Service) { s.ActualDigest = "" }), reg: &fakeRegistry{}, wantNotPoll: "no registry digest"},
+		{name: "removed is not found",
+			svc: auto(func(s *model.Service) { s.RemovedAt = ptr(time.Now()) }), reg: &fakeRegistry{}, wantErr: model.ErrNotFound},
+		{name: "a comparable tag lists the repo once and suggests the newer tag",
+			svc:       newerSvc(1, repoB, "1.27.3"),
+			reg:       newerRegistry(map[string][]string{repoB: {"1.27.4", "1.28.0"}}, repoB+":1.27.3"),
+			wantHeads: []string{repoB + ":1.27.3"}, wantTags: []string{repoB},
+			check: func(t *testing.T, st *fakeStore, j *fakeJobs) {
+				require.Len(t, st.newer, 1)
+				assert.Equal(t, newerCall{1, repoB + ":1.28.0", time.Date(2026, 10, 13, 12, 0, 0, 0, time.UTC)}, st.newer[0])
+			}},
+		{name: "a tag that cannot have a newer tag lists nothing",
+			svc: newerSvc(1, repoB, "latest"), reg: newerRegistry(nil, repoB+":latest"), wantHeads: []string{repoB + ":latest"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			st := &fakeStore{services: []model.Service{tt.svc}}
+			j := &fakeJobs{errFor: map[int64]error{1: tt.startErr}}
+			p, _ := newPoller(st, j, tt.reg, Config{})
+
+			err := p.PollService(context.Background(), 1)
+
+			var np *NotPolledError
+			switch {
+			case tt.wantNotPoll != "":
+				require.ErrorAs(t, err, &np)
+				assert.Equal(t, tt.wantNotPoll, np.Reason)
+			case tt.wantErr != nil:
+				assert.ErrorIs(t, err, tt.wantErr)
+			default:
+				require.NoError(t, err)
+			}
+			assert.Equal(t, tt.wantHeads, tt.reg.sortedCalls())
+			assert.Equal(t, tt.wantTags, tt.reg.tagCalls)
+			if tt.check != nil {
+				tt.check(t, st, j)
+			}
+		})
+	}
+}
+
+func TestPollServiceUnknownID(t *testing.T) {
+	reg := &fakeRegistry{}
+	p, _ := newPoller(&fakeStore{}, &fakeJobs{}, reg, Config{})
+
+	err := p.PollService(context.Background(), 9)
+
+	assert.ErrorIs(t, err, model.ErrNotFound)
+	assert.Empty(t, reg.calls)
+}
+
+func TestPollServiceOnlyThisService(t *testing.T) {
+	ref := repoA + ":1.4"
+	st := &fakeStore{services: []model.Service{svc(1, ref), svc(2, ref)}}
+	reg := &fakeRegistry{digests: map[string]string{ref: "sha256:new"}}
+	p, _ := newPoller(st, &fakeJobs{}, reg, Config{})
+
+	require.NoError(t, p.PollService(context.Background(), 1))
+
+	require.Len(t, st.available, 1)
+	assert.Equal(t, int64(1), st.available[0].id)
+	assert.Equal(t, []string{ref}, reg.sortedCalls())
+	for _, c := range st.pollErrors {
+		assert.NotContains(t, c.ids, int64(2))
+	}
+	for _, c := range st.newer {
+		assert.Equal(t, int64(1), c.id)
+	}
+	for _, c := range st.lastTag {
+		assert.Equal(t, int64(1), c.id)
+	}
+}
+
+func TestPollServiceCancelled(t *testing.T) {
+	ref := repoA + ":1.4"
+	st := &fakeStore{services: []model.Service{svc(1, ref)}}
+	reg := &fakeRegistry{release: make(chan struct{})} // lookups only end by cancel
+	p, _ := newPoller(st, &fakeJobs{}, reg, Config{})
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	err := p.PollService(ctx, 1)
+
+	assert.ErrorIs(t, err, context.Canceled)
+	assert.Empty(t, st.pollErrors)
+	assert.Empty(t, st.available)
+}

internal/master/web/drift_test.go

@@ -281,7 +281,7 @@ func TestServiceDetail_DriftAndMoveData(t *testing.T) {
 			store := &fakeStore{services: []model.Service{live, gone, swarm, container, self},
 				moves: []model.Move{move}, sources: sources}
 			jobs := &fakeJobs{restorable: tt.restorable}
-			s, err := New(store, &fakeHub{}, jobs, events.NewBroker(), Config{}, slog.New(slog.NewTextHandler(io.Discard, nil)))
+			s, err := New(store, &fakeHub{}, jobs, events.NewBroker(), &fakePoller{}, Config{}, slog.New(slog.NewTextHandler(io.Discard, nil)))
 			require.NoError(t, err)
 			req := httptest.NewRequest(http.MethodGet, "/services/"+strconv.FormatInt(tt.id, 10), nil)
 

internal/master/web/poll_test.go

@@ -0,0 +1,86 @@
+package web
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/url"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/shcizo/package-updater/internal/master/model"
+	"github.com/shcizo/package-updater/internal/master/poller"
+)
+
+// fakePoller records the services it was asked to check and answers err.
+type fakePoller struct {
+	mu    sync.Mutex
+	err   error
+	calls []int64
+}
+
+func (f *fakePoller) PollService(_ context.Context, id int64) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.calls = append(f.calls, id)
+	return f.err
+}
+
+func (f *fakePoller) called() []int64 {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]int64(nil), f.calls...)
+}
+
+func TestPollService(t *testing.T) {
+	tests := []struct {
+		name         string
+		id           string
+		err          error
+		wantStatus   int
+		wantLocation string
+		wantBody     string
+		wantCalls    []int64
+	}{
+		{name: "redirects to the service page", id: "1", wantStatus: http.StatusSeeOther, wantLocation: "/services/1", wantCalls: []int64{1}},
+		{name: "unknown service is 404", id: "1", err: model.ErrNotFound, wantStatus: http.StatusNotFound, wantCalls: []int64{1}},
+		{name: "invalid id is 400", id: "abc", wantStatus: http.StatusBadRequest},
+		{name: "not polled is 409 with the reason", id: "1", err: &poller.NotPolledError{Reason: model.ReasonNoTag},
+			wantStatus: http.StatusConflict, wantBody: "Cannot check: follows no tag.", wantCalls: []int64{1}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fp := &fakePoller{err: tt.err}
+			srv, _, _, _, _ := newTestEnvFull(t, func(*Config) {}, fp)
+
+			resp, err := noRedirectClient().PostForm(srv.URL+"/services/"+tt.id+"/poll", url.Values{"csrf_token": {"csrf"}})
+			require.NoError(t, err)
+			defer resp.Body.Close()
+			body, _ := io.ReadAll(resp.Body)
+
+			assert.Equal(t, tt.wantStatus, resp.StatusCode)
+			assert.Equal(t, tt.wantLocation, resp.Header.Get("Location"))
+			assert.Contains(t, string(body), tt.wantBody)
+			assert.Equal(t, tt.wantCalls, fp.called())
+		})
+	}
+}
+
+func TestServicePage_CheckNowForm(t *testing.T) {
+	srv, store, _, _, _ := newTestEnv(t)
+	store.services[0].ActualDigest = "sha256:" + "a"
+	_, body := get(t, srv, "/services/1")
+	assert.Contains(t, body, `action="/services/1/poll"`)
+	assert.Contains(t, body, `<button type="submit">Check now</button>`)
+	assert.NotContains(t, body, "Check unavailable")
+}
+
+func TestServicePage_CheckNowDisabledWhenNotPolled(t *testing.T) {
+	srv, _, _, _, _ := newTestEnv(t)
+	_, body := get(t, srv, "/services/2") // follows no tag
+	assert.Contains(t, body, `<button type="submit" disabled>Check now</button>`)
+	assert.Contains(t, body, "Check unavailable: follows no tag.")
+}

internal/master/web/server.go

@@ -18,6 +18,7 @@ import (
 	"github.com/shcizo/package-updater/internal/agenttoken"
 	"github.com/shcizo/package-updater/internal/master/events"
 	"github.com/shcizo/package-updater/internal/master/model"
+	"github.com/shcizo/package-updater/internal/master/poller"
 	"github.com/shcizo/package-updater/internal/master/web/icons"
 	"github.com/shcizo/package-updater/internal/master/webauth"
 	"github.com/shcizo/package-updater/internal/protocol"
@@ -85,6 +86,13 @@ type Jobs interface {
 	RestoreDesired(ctx context.Context, serviceID int64, requestedBy string) (model.Job, error)
 }
 
+// Poller checks the registry for one service. *poller.Poller satisfies it.
+type Poller interface {
+	// PollService returns *poller.NotPolledError when the service is not
+	// polled and model.ErrNotFound for an unknown or removed one.
+	PollService(ctx context.Context, id int64) error
+}
+
 // Broker delivers change signals to open streams and accepts signals from
 // UI actions. *events.Broker satisfies it.
 type Broker interface {
@@ -108,6 +116,7 @@ type Server struct {
 	hub    Hub
 	jobs   Jobs
 	broker Broker
+	poller Poller
 	cfg    Config
 	log    *slog.Logger
 	now    func() time.Time
@@ -116,7 +125,7 @@ type Server struct {
 
 // New parses the templates. Each page is its own template set so every page
 // can define its own "content" block.
-func New(store Store, hub Hub, jobs Jobs, broker Broker, cfg Config, log *slog.Logger) (*Server, error) {
+func New(store Store, hub Hub, jobs Jobs, broker Broker, poller Poller, cfg Config, log *slog.Logger) (*Server, error) {
 	funcs := template.FuncMap{"shortRef": shortRef, "duration": jobDuration, "followsNoTag": followsNoTag, "middle": middle}
 	pages := map[string]*template.Template{}
 	for _, page := range []string{"overview.html", "agents.html", "service.html", "jobs.html", "job.html"} {
@@ -126,7 +135,7 @@ func New(store Store, hub Hub, jobs Jobs, broker Broker, cfg Config, log *slog.L
 		}
 		pages[page] = t
 	}
-	return &Server{store: store, hub: hub, jobs: jobs, broker: broker, cfg: cfg, log: log, now: time.Now, pages: pages}, nil
+	return &Server{store: store, hub: hub, jobs: jobs, broker: broker, poller: poller, cfg: cfg, log: log, now: time.Now, pages: pages}, nil
 }
 
 // Register adds the UI routes to mux. protect wraps every route except
@@ -140,6 +149,7 @@ func (s *Server) Register(mux *http.ServeMux, protect func(http.Handler) http.Ha
 	route("GET /fragments/services/{id}/jobs", s.serviceJobsFragment)
 	route("POST /services/{id}/update", s.updateService)
 	route("POST /services/{id}/mode", s.setMode)
+	route("POST /services/{id}/poll", s.pollService)
 	route("POST /services/{id}/restore", s.restoreDesired)
 	route("POST /services/{id}/accept", s.acceptRunning)
 	route("POST /services/{id}/merge", s.mergeService)
@@ -204,6 +214,7 @@ type pageData struct {
 	ConfigFiles []string
 	Reason      string // why Service cannot be updated; "" when it can
 	AutoBlocked string // why Service cannot be set to auto; "" when it can
+	PollBlocked string // why Service cannot be checked against the registry; "" when it can
 	Versions    []versionRow
 	NewerTag    string // Service's newer tag while it still holds; "" otherwise
 	Polling     string // what the service page says about registry polling
@@ -380,6 +391,7 @@ func (s *Server) serviceDetail(r *http.Request, id int64) (pageData, error) {
 		return data, err
 	}
 	data.AutoBlocked = s.autoBlocked(svc)
+	data.PollBlocked = pollBlocked(svc)
 	if err := s.jobs.Restorable(svc); errors.As(err, &nu) {
 		data.RestoreBlocked = nu.Reason
 	} else if err != nil {
@@ -605,6 +617,34 @@ func (s *Server) renderServiceError(w http.ResponseWriter, r *http.Request, id i
 	s.page(w, r, status, "service.html", data)
 }
 
+// pollService checks the registry for one service now and waits for the
+// answer. A registry error is not a failure of the request: it shows on the
+// service page as the last check failing. The poller publishes the change
+// itself when it writes.
+func (s *Server) pollService(w http.ResponseWriter, r *http.Request) {
+	id, ok := pathID(w, r)
+	if !ok {
+		return
+	}
+	err := s.poller.PollService(r.Context(), id)
+	var np *poller.NotPolledError
+	switch {
+	case errors.As(err, &np):
+		s.renderServiceError(w, r, id, http.StatusConflict, "Cannot check: "+np.Reason+".")
+		return
+	case r.Context().Err() != nil:
+		// The client is gone or the master is shutting down. Redirect anyway:
+		// a browser still waiting gets the page, not an empty 200.
+	case err != nil:
+		s.failLookup(w, err)
+		return
+	default:
+		sess, _ := webauth.SessionFrom(r.Context())
+		s.log.Info("poll_requested", "service_id", id, "subject", sess.Subject)
+	}
+	http.Redirect(w, r, "/services/"+strconv.FormatInt(id, 10), http.StatusSeeOther)
+}
+
 // setMode switches a service between manual and auto. Manual is always
 // allowed; auto only when jobs.AutoAllowed says so.
 func (s *Server) setMode(w http.ResponseWriter, r *http.Request) {
@@ -628,6 +668,10 @@ func (s *Server) setMode(w http.ResponseWriter, r *http.Request) {
 		}
 		var nu *model.NotUpdatableError
 		if err := s.jobs.AutoAllowed(svc); errors.As(err, &nu) {
+			if isHTMX(r) {
+				// htmx does not swap a 409; the service page shows the reason.
+				w.Header().Set("HX-Redirect", "/services/"+strconv.FormatInt(id, 10))
+			}
 			s.renderServiceError(w, r, id, http.StatusConflict, "Cannot enable auto: "+nu.Reason+".")
 			return
 		} else if err != nil {
@@ -641,6 +685,11 @@ func (s *Server) setMode(w http.ResponseWriter, r *http.Request) {
 	}
 	s.broker.Publish(events.Services)
 	if r.PostFormValue("return") == "overview" {
+		if isHTMX(r) {
+			// Swap the list in place instead of redirecting, so the page keeps its scroll position.
+			s.servicesFragment(w, r)
+			return
+		}
 		http.Redirect(w, r, "/", http.StatusSeeOther)
 		return
 	}
@@ -881,6 +930,11 @@ func (s *Server) fail(w http.ResponseWriter, err error) {
 	http.Error(w, "internal error", http.StatusInternalServerError)
 }
 
+// isHTMX reports whether r was sent by htmx rather than by a plain form submit.
+func isHTMX(r *http.Request) bool {
+	return r.Header.Get("HX-Request") == "true"
+}
+
 // agentSnippet is the compose file shown once when an agent is added.
 func agentSnippet(cfg Config, token string) string {
 	return fmt.Sprintf(`services:

internal/master/web/server_test.go

@@ -232,6 +232,12 @@ func newTestEnvVersion(t *testing.T, version string) (*httptest.Server, *fakeSto
 
 // newTestEnvConfig is newTestEnv with edit applied to the UI's Config.
 func newTestEnvConfig(t *testing.T, edit func(*Config)) (*httptest.Server, *fakeStore, *fakeHub, *events.Broker, *fakeJobs) {
+	t.Helper()
+	return newTestEnvFull(t, edit, &fakePoller{})
+}
+
+// newTestEnvFull is newTestEnvConfig with p as the poller.
+func newTestEnvFull(t *testing.T, edit func(*Config), p Poller) (*httptest.Server, *fakeStore, *fakeHub, *events.Broker, *fakeJobs) {
 	t.Helper()
 	agentID, offlineAgentID := int64(2), int64(3)
 	store := &fakeStore{
@@ -260,7 +266,7 @@ func newTestEnvConfig(t *testing.T, edit func(*Config)) (*httptest.Server, *fake
 		AgentURL: "wss://10.0.0.5:8090/agent", MasterKey: "sha256:abc", AgentImage: "gitea.shcizo.se/shcizo/package-updater:latest",
 	}
 	edit(&cfg)
-	s, err := New(store, hub, jobs, broker, cfg, slog.New(slog.NewTextHandler(io.Discard, nil)))
+	s, err := New(store, hub, jobs, broker, p, cfg, slog.New(slog.NewTextHandler(io.Discard, nil)))
 	require.NoError(t, err)
 	mux := http.NewServeMux()
 	s.Register(mux, func(h http.Handler) http.Handler {
@@ -707,6 +713,47 @@ func TestSetMode_ReturnToOverview(t *testing.T) {
 	assert.Equal(t, "auto", store.modeOf(1))
 }
 
+func postModeHTMX(t *testing.T, srv *httptest.Server, id string, form url.Values) (*http.Response, string) {
+	t.Helper()
+	form.Set("csrf_token", "csrf")
+	req, err := http.NewRequest(http.MethodPost, srv.URL+"/services/"+id+"/mode", strings.NewReader(form.Encode()))
+	require.NoError(t, err)
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("HX-Request", "true")
+	resp, err := noRedirectClient().Do(req)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	body, _ := io.ReadAll(resp.Body)
+	return resp, string(body)
+}
+
+func TestSetMode_HTMXFromOverviewReturnsServicesFragment(t *testing.T) {
+	srv, store, _, broker, _ := newTestEnv(t)
+	sub, cancel := broker.Subscribe()
+	defer cancel()
+
+	resp, body := postModeHTMX(t, srv, "1", url.Values{"mode": {"auto"}, "return": {"overview"}})
+
+	assert.Equal(t, http.StatusOK, resp.StatusCode, "no redirect, so the page keeps its scroll position")
+	assert.Empty(t, resp.Header.Get("Location"))
+	assert.NotContains(t, body, "<html")
+	assert.Contains(t, body, `id="machines" hx-swap-oob`)
+	assert.Contains(t, body, `action="/services/1/mode"`)
+	assert.Equal(t, "auto", store.modeOf(1))
+	assert.Equal(t, events.Services, <-sub)
+}
+
+func TestSetMode_HTMXRefusedRedirectsToService(t *testing.T) {
+	srv, store, _, _, jobs := newTestEnv(t)
+	jobs.autoErr = &model.NotUpdatableError{Reason: model.ReasonBuilt}
+
+	resp, _ := postModeHTMX(t, srv, "1", url.Values{"mode": {"auto"}, "return": {"overview"}})
+
+	assert.Equal(t, http.StatusConflict, resp.StatusCode)
+	assert.Equal(t, "/services/1", resp.Header.Get("HX-Redirect"), "htmx does not swap a 409, so send the user to the page that shows why")
+	assert.Equal(t, "manual", store.modeOf(1))
+}
+
 func TestSetMode_AutoRefusedShows409(t *testing.T) {
 	srv, store, _, _, jobs := newTestEnv(t)
 	jobs.autoErr = &model.NotUpdatableError{Reason: model.ReasonBuilt}

internal/master/web/static/app.css

@@ -66,6 +66,9 @@ summary.btn::-webkit-details-marker{display:none}
 .seg button{display:inline-flex;align-items:center;gap:6px;height:28px;padding:0 10px;border:0;border-radius:5px;background:transparent;color:var(--mut);font:500 12.5px var(--sans);cursor:pointer}
 .seg button:hover{color:var(--fg)}
 .seg button[aria-pressed=true]{background:var(--hover);color:var(--fg);box-shadow:inset 0 0 0 1px var(--line2)}
+/* htmx inserts the new list before removing the old one; scroll anchoring on the
+   focused switch would scroll by the list height and then land at the bottom. */
+#services{overflow-anchor:none}
 .grp{margin-top:28px}
 .gh{display:flex;flex-wrap:wrap;align-items:baseline;gap:4px 12px;padding-bottom:8px;border-bottom:2px solid var(--fg)}
 .gh h2{margin:0;font:700 20px var(--sans);letter-spacing:-.015em}

internal/master/web/templates/overview.html

@@ -83,7 +83,7 @@
       {{if .Self}}<span class="tag f-out">This agent</span>{{end}}
     </div>
     <div class="mode">
-      <form method="post" action="/services/{{.ID}}/mode">
+      <form method="post" action="/services/{{.ID}}/mode" hx-post="/services/{{.ID}}/mode" hx-target="#services" hx-swap="innerHTML">
         <input type="hidden" name="csrf_token" value="{{$.CSRF}}">
         <input type="hidden" name="return" value="overview">
         {{if eq .UpdateMode "auto"}}<input type="hidden" name="mode" value="manual">

internal/master/web/templates/service.html

@@ -23,6 +23,11 @@
 </form>
 <p class="muted">Pulls the current tag again and redeploys the service.</p>
 {{end}}
+<form method="post" action="/services/{{.Service.ID}}/poll">
+  <input type="hidden" name="csrf_token" value="{{.CSRF}}">
+  <button type="submit"{{if .PollBlocked}} disabled{{end}}>Check now</button>
+  <p class="muted">{{if .PollBlocked}}Check unavailable: {{.PollBlocked}}.{{else}}Asks the registry now instead of waiting for the next poll.{{end}}</p>
+</form>
 <form method="post" action="/services/{{.Service.ID}}/mode">
   <input type="hidden" name="csrf_token" value="{{.CSRF}}">
   {{if eq .Service.UpdateMode "auto"}}<input type="hidden" name="mode" value="manual">

internal/master/web/views.go

@@ -281,6 +281,15 @@ func versionRows(versions []model.ImageVersion, actualDigest string) []versionRo
 	return rows
 }
 
+// pollBlocked returns why the registry cannot be checked for svc, or "" when
+// it can.
+func pollBlocked(svc model.Service) string {
+	if svc.RemovedAt != nil {
+		return model.ReasonRemoved
+	}
+	return poller.SkipReason(svc)
+}
+
 // pollingStatus is the text of the "Polling" row on the service page and
 // whether it is a registry error.
 func pollingStatus(svc model.Service, interval time.Duration) (text string, failed bool) {