mangleDuration := prometheus.NewHistogramVec(
prometheus.HistogramOpts{
Name: "mangle_html_duration_seconds",
Help: "Time spent processing HTML",
Buckets: []float64{.001, .005, .01, .05, .1, .5},
},
[]string{"status"},
)
I want to add a custom metric into caddy,what should I do?
Use this:
func (m *ContentFilter) Provision(ctx caddy.Context) error {
var registerErr error
if reg := ctx.GetMetricsRegistry(); reg != nil {
registerOnce.Do(func() {
logrus.Infof("Registing metric: %s", "mangle_html_duration_seconds")
if err := reg.Register(mangleDuration); err != nil {
registerErr = fmt.Errorf("failed to register metrics: %v", err)
}
})
}
return registerErr
}
timer := prometheus.NewTimer(prometheus.ObserverFunc(func(v float64) {
mangleDuration.WithLabelValues("status").Observe(v)
}))
defer timer.ObserveDuration()
I’m new to Caddy, why is the metric not showing up after registration?
Did you initiate any requests that affect the values of the metric? Metrics only show up when their values change from the initial one. Show us how you’re testing.
var (
mangleDuration = prometheus.NewHistogramVec(
prometheus.HistogramOpts{
Name: "mangle_html_duration_seconds",
Help: "Time spent processing HTML",
Buckets: []float64{1, 5, 10, 50, 100, 500},
},
[]string{"status"},
)
registerOnce sync.Once
)
func mangleHTML(input []byte) ([]byte, bool) {
var (
buf bytes.Buffer
err error
doc *html.Node
)
timer := prometheus.NewTimer(prometheus.ObserverFunc(func(v float64) {
mangleDuration.WithLabelValues("success").Observe(v)
logrus.Infof("mangleHTML invoke spent %.3f", v*1000)
}))
defer timer.ObserveDuration()
......
}
func (m *ContentFilter) Provision(ctx caddy.Context) error {
var registerErr error
if reg := ctx.GetMetricsRegistry(); reg != nil {
registerOnce.Do(func() {
logrus.Infof("Registing metric: %s", "mangle_html_duration_seconds")
if err := reg.Register(mangleDuration); err != nil {
registerErr = fmt.Errorf("failed to register metrics: %v", err)
}
})
}
return registerErr
}
I wrote a Caddy module that intercepts reverse proxy responses to sanitize HTML. I can confirm that this method has been called, as shown in the logs below.
time="2025-04-16T17:48:21+08:00" level=info msg="mangleHTML invoke spent 17.520"
time="2025-04-16T17:48:21+08:00" level=info msg="request url: 127.0.0.1:64839/be7e29b0e84f/avatar/05bb842f87f5c312304d66352d694b02 replace to -> 127.0.0.1:64839/avatar/05bb842f87f5c312304d66352d694b02\n"
I’ve already integrated Caddy metrics into Grafana.
version: "3.8"
services:
prometheus:
image: prom/prometheus:latest
container_name: prometheus
ports:
- "9090:9090"
volumes:
- ./prometheus.yml:/etc/prometheus/prometheus.yml
restart: unless-stopped
grafana:
image: grafana/grafana-oss:latest
container_name: grafana
ports:
- "3000:3000"
restart: unless-stopped
global:
scrape_interval: 5s
scrape_configs:
- job_name: 'caddy'
static_configs:
- targets: ['10.21.177.52:2019']
