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// Copyright 2020 Matthew Holt and The Caddy Authors
//
// 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.
package metrics
import (
"net/http"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
"go.uber.org/zap"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
)
func init() {
caddy.RegisterModule(Metrics{})
httpcaddyfile.RegisterHandlerDirective("metrics", parseCaddyfile)
}
// Metrics is a module that serves a /metrics endpoint so that any gathered
// metrics can be exposed for scraping. This module is configurable by end-users
// unlike AdminMetrics.
type Metrics struct {
metricsHandler http.Handler
// Disable OpenMetrics negotiation, enabled by default. May be necessary if
// the produced metrics cannot be parsed by the service scraping metrics.
DisableOpenMetrics bool `json:"disable_openmetrics,omitempty"`
}
// CaddyModule returns the Caddy module information.
func (Metrics) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "http.handlers.metrics",
New: func() caddy.Module { return new(Metrics) },
}
}
type zapLogger struct {
zl *zap.Logger
}
func (l *zapLogger) Println(v ...any) {
l.zl.Sugar().Error(v...)
}
// Provision sets up m.
func (m *Metrics) Provision(ctx caddy.Context) error {
log := ctx.Logger()
m.metricsHandler = createMetricsHandler(&zapLogger{log}, !m.DisableOpenMetrics)
return nil
}
func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error) {
var m Metrics
err := m.UnmarshalCaddyfile(h.Dispenser)
return m, err
}
// UnmarshalCaddyfile sets up the handler from Caddyfile tokens. Syntax:
//
// metrics [<matcher>] {
// disable_openmetrics
// }
func (m *Metrics) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
for d.Next() {
args := d.RemainingArgs()
if len(args) > 0 {
return d.ArgErr()
}
for d.NextBlock(0) {
switch d.Val() {
case "disable_openmetrics":
m.DisableOpenMetrics = true
default:
return d.Errf("unrecognized subdirective %q", d.Val())
}
}
}
return nil
}
func (m Metrics) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
m.metricsHandler.ServeHTTP(w, r)
return nil
}
// Interface guards
var (
_ caddy.Provisioner = (*Metrics)(nil)
_ caddyhttp.MiddlewareHandler = (*Metrics)(nil)
_ caddyfile.Unmarshaler = (*Metrics)(nil)
)
func createMetricsHandler(logger promhttp.Logger, enableOpenMetrics bool) http.Handler {
return promhttp.InstrumentMetricHandler(prometheus.DefaultRegisterer,
promhttp.HandlerFor(prometheus.DefaultGatherer, promhttp.HandlerOpts{
// will only log errors if logger is non-nil
ErrorLog: logger,
// Allow OpenMetrics format to be negotiated - largely compatible,
// except quantile/le label values always have a decimal.
EnableOpenMetrics: enableOpenMetrics,
}),
)
}
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