Clarify and clean up template contract for status (#149)

* Clarify and clean up template contract for status

Ring was passing a mix of time.Time and formatted string for the time:
unified to pass always time.Time, and decide what to do when rendering.
This will allow us some extra customisation if replacing the template
with a non-default one.

Also replaced the "Unhealthy" state by "UNHEALTHY" in the template,
because the rest of states are uppercase. Not replacing the constant
value because it's being used for metrics and we'd have to fix the
recording rules in all the downstream projects.

Changed how heartbeat time is rendered: rendering the duration since the
heartbeat and the time in parenthesis: heartbeats are so common that
showing a date doesn't make sense, and since they're usually few seconds
away, the "duration ago" is what makes more sense IMO.

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Update CHANGELOG.md

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Use only 2 decimals for percentage

We don't need 4

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Add 'Content-Type: text/html' header

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

CHANGELOG.md

@@ -22,6 +22,7 @@
 * [CHANGE] ring/client: It's now possible to set different value than `consul` as default KV store. #120
 * [CHANGE] Lifecycler: Default value of lifecycler's `final-sleep` is now `0s` (i.e. no sleep). #121
 * [CHANGE] Lifecycler: It's now possible to change default value of lifecycler's `final-sleep`. #121
+* [CHANGE] Minor cosmetic changes in ring and memberlist HTTP status templates. #149
 * [ENHANCEMENT] Add middleware package. #38
 * [ENHANCEMENT] Add the ring package #45
 * [ENHANCEMENT] Add limiter package. #41

kv/memberlist/kv_init_service.go

@@ -171,21 +171,14 @@ func (kvs *KVInitService) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	if strings.Contains(accept, "application/json") {
 		w.Header().Set("Content-Type", "application/json")
 
-		data, err := json.Marshal(v)
-		if err != nil {
+		if err := json.NewEncoder(w).Encode(v); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
 		}
-
-		// We ignore errors here, because we cannot do anything about them.
-		// Write will trigger sending Status code, so we cannot send a different status code afterwards.
-		// Also this isn't internal error, but error communicating with client.
-		_, _ = w.Write(data)
 		return
 	}
 
-	err := defaultPageTemplate.Execute(w, v)
-	if err != nil {
+	w.Header().Set("Content-Type", "text/html")
+	if err := defaultPageTemplate.Execute(w, v); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 	}
 }
@@ -226,7 +219,6 @@ func viewKey(w http.ResponseWriter, store map[string]valueDesc, key string, form
 }
 
 func formatValue(w http.ResponseWriter, val interface{}, format string) {
-
 	w.WriteHeader(200)
 	w.Header().Add("content-type", "text/plain")
 

ring/http.go

@@ -17,26 +17,36 @@ import (
 var defaultPageContent string
 var defaultPageTemplate = template.Must(template.New("webpage").Funcs(template.FuncMap{
 	"mod": func(i, j int) bool { return i%j == 0 },
+	"humanFloat": func(f float64) string {
+		return fmt.Sprintf("%.2g", f)
+	},
+	"timeOrEmptyString": func(t time.Time) string {
+		if t.IsZero() {
+			return ""
+		}
+		return t.Format(time.RFC3339Nano)
+	},
+	"durationSince": func(t time.Time) string { return time.Since(t).Truncate(time.Millisecond).String() },
 }).Parse(defaultPageContent))
 
-type ingesterDesc struct {
-	ID                  string   `json:"id"`
-	State               string   `json:"state"`
-	Address             string   `json:"address"`
-	HeartbeatTimestamp  string   `json:"timestamp"`
-	RegisteredTimestamp string   `json:"registered_timestamp"`
-	Zone                string   `json:"zone"`
-	Tokens              []uint32 `json:"tokens"`
-	NumTokens           int      `json:"-"`
-	Ownership           float64  `json:"-"`
-}
-
 type httpResponse struct {
 	Ingesters  []ingesterDesc `json:"shards"`
 	Now        time.Time      `json:"now"`
 	ShowTokens bool           `json:"-"`
 }
 
+type ingesterDesc struct {
+	ID                  string    `json:"id"`
+	State               string    `json:"state"`
+	Address             string    `json:"address"`
+	HeartbeatTimestamp  time.Time `json:"timestamp"`
+	RegisteredTimestamp time.Time `json:"registered_timestamp"`
+	Zone                string    `json:"zone"`
+	Tokens              []uint32  `json:"tokens"`
+	NumTokens           int       `json:"-"`
+	Ownership           float64   `json:"-"`
+}
+
 type ringAccess interface {
 	casRing(ctx context.Context, f func(in interface{}) (out interface{}, retry bool, err error)) error
 	getRing(context.Context) (*Desc, error)
@@ -85,7 +95,7 @@ func (h *ringPageHandler) handle(w http.ResponseWriter, req *http.Request) {
 	}
 	_, ownedTokens := ringDesc.countTokens()
 
-	ingesterIDs := []string{}
+	var ingesterIDs []string
 	for id := range ringDesc.Ingesters {
 		ingesterIDs = append(ingesterIDs, id)
 	}
@@ -95,24 +105,17 @@ func (h *ringPageHandler) handle(w http.ResponseWriter, req *http.Request) {
 	var ingesters []ingesterDesc
 	for _, id := range ingesterIDs {
 		ing := ringDesc.Ingesters[id]
-		heartbeatTimestamp := time.Unix(ing.Timestamp, 0)
 		state := ing.State.String()
 		if !ing.IsHealthy(Reporting, h.heartbeatPeriod, now) {
-			state = unhealthy
-		}
-
-		// Format the registered timestamp.
-		registeredTimestamp := ""
-		if ing.RegisteredTimestamp != 0 {
-			registeredTimestamp = ing.GetRegisteredAt().String()
+			state = "UNHEALTHY"
 		}
 
 		ingesters = append(ingesters, ingesterDesc{
 			ID:                  id,
 			State:               state,
 			Address:             ing.Addr,
-			HeartbeatTimestamp:  heartbeatTimestamp.String(),
-			RegisteredTimestamp: registeredTimestamp,
+			HeartbeatTimestamp:  time.Unix(ing.Timestamp, 0).UTC(),
+			RegisteredTimestamp: ing.GetRegisteredAt().UTC(),
 			Tokens:              ing.Tokens,
 			Zone:                ing.Zone,
 			NumTokens:           len(ing.Tokens),
@@ -138,8 +141,8 @@ func renderHTTPResponse(w http.ResponseWriter, v httpResponse, t *template.Templ
 		return
 	}
 
-	err := t.Execute(w, v)
-	if err != nil {
+	w.Header().Set("Content-Type", "text/html")
+	if err := t.Execute(w, v); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 	}
 }
@@ -161,14 +164,7 @@ func (h *ringPageHandler) forget(ctx context.Context, id string) error {
 func writeJSONResponse(w http.ResponseWriter, v httpResponse) {
 	w.Header().Set("Content-Type", "application/json")
 
-	data, err := json.Marshal(v)
-	if err != nil {
+	if err := json.NewEncoder(w).Encode(v); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
 	}
-
-	// We ignore errors here, because we cannot do anything about them.
-	// Write will trigger sending Status code, so we cannot send a different status code afterwards.
-	// Also this isn't internal error, but error communicating with client.
-	_, _ = w.Write(data)
 }

ring/status.gohtml

@@ -35,10 +35,10 @@
             <td>{{ .Zone }}</td>
             <td>{{ .State }}</td>
             <td>{{ .Address }}</td>
-            <td>{{ .RegisteredTimestamp }}</td>
-            <td>{{ .HeartbeatTimestamp }}</td>
+            <td>{{ .RegisteredTimestamp | timeOrEmptyString }}</td>
+            <td>{{ .HeartbeatTimestamp | durationSince }} ago ({{ .HeartbeatTimestamp.Format "15:04:05.999" }})</td>
             <td>{{ .NumTokens }}</td>
-            <td>{{ .Ownership }}%</td>
+            <td>{{ .Ownership | humanFloat }}%</td>
             <td>
                 <button name="forget" value="{{ .ID }}" type="submit">Forget</button>
             </td>