fix: address review findings for self-update (#15)

internal/master/webhook/webhook.go

@@ -15,6 +15,7 @@ import (
 	"log/slog"
 	"net/http"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -181,6 +182,9 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	resp := response{RequestID: requestID, Image: req.Image, Tag: req.Tag, Matched: len(services)}
 	pending := map[int]int64{} // index into resp.Results -> job ID
+	// An agent's own service goes last: jobs that reach an agent while it
+	// replaces itself are lost, and messages to one agent arrive in order.
+	slices.SortStableFunc(services, func(a, b model.Service) int { return selfRank(a) - selfRank(b) })
 	for _, svc := range services {
 		res, job := h.handle(work, svc, req.Tag, started, log)
 		resp.Results = append(resp.Results, res)
@@ -252,6 +256,14 @@ func (h *Handler) handle(ctx context.Context, svc model.Service, tag string, sta
 	return res, nil
 }
 
+// selfRank sorts an agent's own service after all others.
+func selfRank(svc model.Service) int {
+	if svc.Self {
+		return 1
+	}
+	return 0
+}
+
 func (h *Handler) setJob(res *result, job model.Job) {
 	res.JobID = job.ID
 	res.JobURL = h.cfg.PublicURL + "/jobs/" + strconv.FormatInt(job.ID, 10)

internal/master/webhook/webhook_test.go

@@ -500,6 +500,21 @@ func TestMixedAutoAndManual(t *testing.T) {
 	assert.Len(t, e.store.avail, 3)
 }
 
+func TestAgentsOwnServiceIsStartedLast(t *testing.T) {
+	own := compose(1, model.ModeAuto, slusk+":1")
+	own.Self = true
+	e := newEnv(t, own, compose(2, model.ModeAuto, slusk+":1"))
+	e.jobs.jobFor[1] = model.Job{Status: model.JobSucceeded}
+	e.jobs.jobFor[2] = model.Job{Status: model.JobSucceeded}
+
+	e.post(`{"image":"` + slusk + `","tag":"2"}`)
+
+	calls := e.jobs.startCalls()
+	require.Len(t, calls, 2)
+	assert.Equal(t, int64(2), calls[0].svc.ID)
+	assert.Equal(t, int64(1), calls[1].svc.ID)
+}
+
 func TestClientCancelStopsWaitingButNotStarting(t *testing.T) {
 	e := newEnv(t, compose(1, model.ModeAuto, slusk+":1.4.2"))
 	e.h.cfg.Timeout = time.Minute