[prism] Add a debugz page to standalone web ui. (#28183)

sdks/go/pkg/beam/runners/prism/internal/web/assets/style.css

@@ -83,6 +83,20 @@ header {
     align-items: center;
 }
 
+footer {
+    width: 100%;
+    height: 50px;
+    position: absolute;
+    bottom: 0;
+    left: 0;
+    right: 0;
+    display: flex;
+    justify-content: space-between;
+    background-color: var(--beam-light-orange);
+    padding: 5px 10px;
+    align-items: center;
+}
+
 .logo {
     color: var(--beam-white);
 }
@@ -125,6 +139,12 @@ header {
         padding-bottom: 10px;
     }
 
+    footer {
+        flex-direction: column;
+        height: auto;
+        padding-top: 10px;
+    }
+
     .logo {
         display: inline-block;
         margin-bottom: 10px;

sdks/go/pkg/beam/runners/prism/internal/web/debugz.go

@@ -0,0 +1,150 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements.  See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License.  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package web
+
+import (
+	"fmt"
+	"runtime/debug"
+	"runtime/metrics"
+	"runtime/pprof"
+	"strings"
+)
+
+type debugzData struct {
+	Metrics []goRuntimeMetric
+
+	errorHolder
+}
+
+type goRuntimeMetric struct {
+	Name, Value, Description string
+}
+
+func dumpMetrics() debugzData {
+	// Get descriptions for all supported metrics.
+	descs := metrics.All()
+
+	// Create a sample for each metric.
+	samples := make([]metrics.Sample, len(descs))
+	for i := range samples {
+		samples[i].Name = descs[i].Name
+	}
+
+	// Sample the metrics. Re-use the samples slice if you can!
+	metrics.Read(samples)
+
+	var data debugzData
+
+	// Iterate over all results.
+	for i, sample := range samples {
+		// Pull out the name and value.
+		name, value := sample.Name, sample.Value
+
+		m := goRuntimeMetric{
+			Name:        name,
+			Description: descs[i].Description,
+		}
+
+		// Handle each sample.
+		switch value.Kind() {
+		case metrics.KindUint64:
+			m.Value = fmt.Sprintf("%d", value.Uint64())
+		case metrics.KindFloat64:
+			m.Value = fmt.Sprintf("%f", value.Float64())
+		case metrics.KindFloat64Histogram:
+			m.Value = fmt.Sprintf("%f", medianBucket(value.Float64Histogram()))
+			// The histogram may be quite large, so let's just pull out
+			// a crude estimate for the median for the sake of this example.
+		case metrics.KindBad:
+			// This should never happen because all metrics are supported
+			// by construction.
+			m.Value = "bug in runtime/metrics package: KindBad"
+		default:
+			// This may happen as new metrics get added.
+			//
+			// The safest thing to do here is to simply log it somewhere
+			// as something to look into, but ignore it for now.
+			// In the worst case, you might temporarily miss out on a new metric.
+			m.Value = fmt.Sprintf("%s: unexpected metric Kind: %v - %s\n", name, value.Kind(), descs[i].Description)
+		}
+		data.Metrics = append(data.Metrics, m)
+	}
+
+	var b strings.Builder
+	buildInfo(&b)
+
+	data.Metrics = append(data.Metrics, goRuntimeMetric{
+		Name:        "BUILD INFO",
+		Value:       "n/a",
+		Description: b.String(),
+	})
+
+	b.Reset()
+	goroutineDump(&b)
+	data.Metrics = append(data.Metrics, goRuntimeMetric{
+		Name:        "GOROUTINES",
+		Value:       "n/a",
+		Description: b.String(),
+	})
+
+	b.Reset()
+	profiles(&b)
+
+	data.Metrics = append(data.Metrics, goRuntimeMetric{
+		Name:        "PROFILES",
+		Value:       b.String(),
+		Description: "List of available runtime/pprof profiles.",
+	})
+	return data
+}
+
+func goroutineDump(statusInfo *strings.Builder) {
+	profile := pprof.Lookup("goroutine")
+	if profile != nil {
+		profile.WriteTo(statusInfo, 1)
+	}
+}
+
+func buildInfo(statusInfo *strings.Builder) {
+	if info, ok := debug.ReadBuildInfo(); ok {
+		statusInfo.WriteString(info.String())
+	}
+}
+
+func profiles(statusInfo *strings.Builder) {
+	ps := pprof.Profiles()
+	statusInfo.WriteString(fmt.Sprintf("profiles %v\n", len(ps)))
+	for _, p := range ps {
+		statusInfo.WriteString(p.Name())
+		statusInfo.WriteRune('\n')
+	}
+}
+
+func medianBucket(h *metrics.Float64Histogram) float64 {
+	total := uint64(0)
+	for _, count := range h.Counts {
+		total += count
+	}
+	thresh := total / 2
+	total = 0
+	for i, count := range h.Counts {
+		total += count
+		if total >= thresh {
+			return h.Buckets[i]
+		}
+	}
+	panic("should not happen")
+}

sdks/go/pkg/beam/runners/prism/internal/web/debugz.html

@@ -0,0 +1,50 @@
+{{/*
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. See accompanying LICENSE file.
+*/}}
+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <meta http-equiv="X-UA-Compatible" content="ie=edge" />
+  <title>Debug Metrics - Beam Prism</title>
+  <link rel="stylesheet" href="/assets/style.css" />
+</head>
+
+<body>
+  <main>
+    <header>
+      <a class="logo" href="/">Debug Metrics - Beam Prism</a>
+    </header>
+    <section class="container">
+      {{ if .Error}}{{.Error}}{{end}}
+      <table class="main-table">
+        <thead>
+          <td>ID</td>
+          <td>Name</td>
+          <td>State</td>
+        </thead>
+        {{ range .Metrics }}
+        <tr>
+          <td>{{ .Name }}</td>
+          <td style="white-space: pre">{{ .Value }}</td>
+          <td style="white-space: pre">{{ .Description }}</td>
+        </tr>
+        {{ else }}
+        <tr>
+          <td>No metrics have been returned.</td>
+        </tr>
+        {{ end }}
+      </table>
+    </section>
+  </main>
+</body>

sdks/go/pkg/beam/runners/prism/internal/web/index.html

@@ -47,5 +47,8 @@
         {{ end }}
       </table>
     </section>
+    <footer>
+      <a class="logo" href="debugz">debugz</a>
+    </footer>
   </main>
 </body>

sdks/go/pkg/beam/runners/prism/internal/web/web.go

@@ -46,12 +46,16 @@ var indexTemplate string
 //go:embed jobdetails.html
 var jobTemplate string
 
+//go:embed debugz.html
+var debugzTemplate string
+
 //go:embed assets/*
 var assets embed.FS
 
 var (
-	indexPage = template.Must(template.New("index").Parse(indexTemplate))
-	jobPage   = template.Must(template.New("job").Parse(jobTemplate))
+	indexPage  = template.Must(template.New("index").Parse(indexTemplate))
+	jobPage    = template.Must(template.New("job").Parse(jobTemplate))
+	debugzPage = template.Must(template.New("debugz").Parse(debugzTemplate))
 )
 
 type pTransform struct {
@@ -284,13 +288,22 @@ func (h *jobsConsoleHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	renderPage(indexPage, data, w)
 }
 
+type debugzHandler struct {
+}
+
+func (h *debugzHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	data := dumpMetrics()
+	renderPage(debugzPage, &data, w)
+}
+
 // Initialize the web client to talk to the given Job Management Client.
 func Initialize(ctx context.Context, port int, jobcli jobpb.JobServiceClient) error {
 	assetsFs := http.FileServer(http.FS(assets))
 	mux := http.NewServeMux()
 
 	mux.Handle("/assets/", assetsFs)
 	mux.Handle("/job/", &jobDetailsHandler{Jobcli: jobcli})
+	mux.Handle("/debugz", &debugzHandler{})
 	mux.Handle("/", &jobsConsoleHandler{Jobcli: jobcli})
 
 	endpoint := fmt.Sprintf("localhost:%d", port)