Monorepo for Tangled
appview/metrics: setup basic prometheus metrics
Signed-off-by: Anirudh Oppiliappan <anirudh@tangled.org>
Anirudh Oppiliappan
(May 11, 2026, 10:50 PM +0300)
f09f595d
b601af9c
+72
+1
appview/config/config.go
+1
appview/config/config.go
···
14
14
CookieSecret string `env:"COOKIE_SECRET, default=00000000000000000000000000000000"`
15
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DbPath string `env:"DB_PATH, default=appview.db"`
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ListenAddr string `env:"LISTEN_ADDR, default=0.0.0.0:3000"`
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+
MetricsListenAddr string `env:"METRICS_LISTEN_ADDR, default=0.0.0.0:9090"`
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AppviewHost string `env:"APPVIEW_HOST, default=tangled.org"`
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AppviewName string `env:"APPVIEW_NAME, default=Tangled"`
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Dev bool `env:"DEV, default=false"`
+19
appview/metrics/metrics.go
+19
appview/metrics/metrics.go
···
1
+
package metrics
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+
3
+
import (
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+
"github.com/prometheus/client_golang/prometheus"
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+
"github.com/prometheus/client_golang/prometheus/promauto"
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+
)
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+
8
+
var (
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+
HttpRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
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Name: "appview_http_requests_total",
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Help: "Total number of HTTP requests",
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}, []string{"method", "path", "status"})
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+
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HttpRequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
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Name: "appview_http_request_duration_seconds",
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Help: "HTTP request duration in seconds",
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Buckets: prometheus.DefBuckets,
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}, []string{"method", "path", "status"})
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)
+40
appview/metrics/middleware.go
+40
appview/metrics/middleware.go
···
1
+
package metrics
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+
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+
import (
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"fmt"
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+
"net/http"
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+
"time"
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+
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"github.com/go-chi/chi/v5"
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)
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+
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type statusRecorder struct {
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http.ResponseWriter
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status int
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}
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+
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func (r *statusRecorder) WriteHeader(status int) {
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r.status = status
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r.ResponseWriter.WriteHeader(status)
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}
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+
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func Middleware(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
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start := time.Now()
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+
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next.ServeHTTP(rec, r)
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+
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// use the matched route pattern to avoid high cardinality
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routePattern := chi.RouteContext(r.Context()).RoutePattern()
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if routePattern == "" {
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routePattern = "unknown"
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}
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+
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status := fmt.Sprintf("%d", rec.status)
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+
duration := time.Since(start).Seconds()
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+
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HttpRequestsTotal.WithLabelValues(r.Method, routePattern, status).Inc()
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HttpRequestDuration.WithLabelValues(r.Method, routePattern, status).Observe(duration)
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})
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+
}
+3
appview/state/router.go
+3
appview/state/router.go
···
11
11
"tangled.org/core/appview/issues"
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"tangled.org/core/appview/knots"
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"tangled.org/core/appview/labels"
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+
"tangled.org/core/appview/metrics"
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"tangled.org/core/appview/middleware"
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"tangled.org/core/appview/migration"
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"tangled.org/core/appview/notifications"
···
37
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s.rdb,
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s.logger,
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)
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+
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router.Use(metrics.Middleware)
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m := migration.NewMigration(s.db, s.oauth, s.idResolver.Directory(), s.logger)
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router.Use(m.BackgroundMigrationMiddleware)
+9
cmd/appview/main.go
+9
cmd/appview/main.go
···
5
5
"net/http"
6
6
"os"
7
7
8
+
"github.com/prometheus/client_golang/prometheus/promhttp"
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"tangled.org/core/appview/config"
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"tangled.org/core/appview/state"
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tlog "tangled.org/core/log"
···
34
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}
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logger.Info("starting server", "address", c.Core.ListenAddr)
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+
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go func() {
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logger.Info("starting metrics server", "address", c.Core.MetricsListenAddr)
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http.Handle("/metrics", promhttp.Handler())
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if err := http.ListenAndServe(c.Core.MetricsListenAddr, nil); err != nil {
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logger.Error("failed to start metrics server", "err", err)
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+
}
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}()
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if err := http.ListenAndServe(c.Core.ListenAddr, state.Router()); err != nil {
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logger.Error("failed to start appview", "err", err)