Merge pull request #8 from peterbourgon/decls-endpoint

Add -declpath flag

Author: peterbourgon

README.md

@@ -1,4 +1,4 @@
-# Prometheus metrics aggregator [![Latest Release](https://img.shields.io/github/release/peterbourgon/prometheus-aggregator.svg?style=flat-square)](https://github.com/peterbourgon/prometheus-aggregator/releases/latest) [![Travis CI](https://travis-ci.org/peterbourgon/prometheus-aggregator.svg?branch=master)](https://travis-ci.org/peterbourgon/prometheus-aggregator) 
+# Prometheus metrics aggregator [![Latest Release](https://img.shields.io/github/release/peterbourgon/prometheus-aggregator.svg?style=flat-square)](https://github.com/peterbourgon/prometheus-aggregator/releases/latest) [![Build Status](https://img.shields.io/endpoint.svg?url=https%3A%2F%2Factions-badge.atrox.dev%2Fpeterbourgon%2Fprometheus-aggregator%2Fbadge&style=flat-square&label=build)](https://github.com/peterbourgon/prometheus-aggregator/actions?query=workflow%3ATest)
 
 Receive and aggregate metrics for consumption by a Prometheus server.
 
@@ -47,13 +47,14 @@ USAGE
 FLAGS
   -debug false                              log debug information
   -declfile ...                             file containing JSON metric declarations
+  -declpath ...                             sibling path to /metrics serving initial metric declarations
   -example false                            print example declfile to stdout and return
   -prometheus tcp://127.0.0.1:8192/metrics  address for Prometheus scrapes
   -socket tcp://127.0.0.1:8191              address for direct socket metric writes
   -strict false                             disconnect clients when they send bad data
 
 VERSION
-  0.0.12
+  0.0.14
 ```
 
 ## How it works
@@ -92,6 +93,11 @@ a file containing a JSON array of multiple JSON objects, and pass it to the
 program at startup via the `-declfile` flag. Or mix and match both! Life is
 full of possibility.
 
+New! Exciting! Great Value! An optional `-declpath` flag allows you to serve
+your initial metric declarations on a sibling path to your Prometheus metrics
+telemetry. This can be useful if you want to programmatically verify the state
+of a prometheus-aggregator instance.
+
 ## Prometheus exposition format
 
 If serializing JSON is a bottleneck, you can optionally emit observations (but
@@ -131,7 +137,7 @@ Histograms are supported too. Provide buckets with the declaration.
 
 ```
 {"name": "myapp_req_dur_seconds", "type": "histogram",
-  "help": "Duration of request in seconds.", 
+  "help": "Duration of request in seconds.",
     "buckets": [0.01, 0.05, 0.1, 0.5, 1, 2, 5, 10]}
 myapp_req_dur_seconds{} 0.0123
 myapp_req_dur_seconds{} 0.99

main.go

@@ -29,6 +29,7 @@ func main() {
 		sockAddr = fs.String("socket", "tcp://127.0.0.1:8191", "address for direct socket metric writes")
 		promAddr = fs.String("prometheus", "tcp://127.0.0.1:8192/metrics", "address for Prometheus scrapes")
 		declfile = fs.String("declfile", "", "file containing JSON metric declarations")
+		declpath = fs.String("declpath", "", "sibling path to /metrics serving initial metric declarations")
 		example  = fs.Bool("example", false, "print example declfile to stdout and return")
 		debug    = fs.Bool("debug", false, "log debug information")
 		strict   = fs.Bool("strict", false, "disconnect clients when they send bad data")
@@ -77,6 +78,7 @@ func main() {
 		}
 	}
 
+	var socketLn net.Listener
 	var forwardFunc func() error
 	var forwardClose func() error
 	{
@@ -118,46 +120,75 @@ func main() {
 				level.Error(logger).Log("socket", *sockAddr, "err", err)
 				os.Exit(1)
 			}
+			socketLn = ln
 			forwardFunc = func() error { return forwardListener(ln, u, *strict, logger) }
 			forwardClose = ln.Close
 		}
 	}
 
-	var promLn net.Listener
-	var promPath string
+	var metricsLn net.Listener
+	var metricsPath string
 	{
 		u, err := url.Parse(*promAddr)
 		if err != nil {
 			level.Error(logger).Log("prometheus", *promAddr, "err", err)
 			os.Exit(1)
 		}
-		promLn, err = net.Listen(u.Scheme, u.Host)
+		metricsLn, err = net.Listen(u.Scheme, u.Host)
 		if err != nil {
 			level.Error(logger).Log("prometheus", *promAddr, "err", err)
 			os.Exit(1)
 		}
-		promPath = u.Path
-		if promPath == "" {
-			promPath = "/"
+		metricsPath = u.Path
+		if metricsPath == "" {
+			metricsPath = "/"
+		}
+	}
+
+	var declPath string
+	var declHandler http.Handler
+	{
+		if *declpath != "" {
+			*declpath = "/" + strings.Trim(*declpath, "/ ")
+			scheme := metricsLn.Addr().Network()
+			hostport := metricsLn.Addr().String()
+			u, err := url.Parse(scheme + "://" + hostport + *declpath)
+			if err != nil {
+				level.Error(logger).Log("declpath", *declpath, "err", err)
+				os.Exit(1)
+			}
+			declPath = u.Path
+			declHandler = http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+				w.Header().Set("content-type", "application/json; charset=utf-8")
+				p, _ := json.MarshalIndent(initial, "", "    ")
+				w.Write(p)
+			})
 		}
 	}
 
 	var g run.Group
 	{
 		g.Add(func() error {
-			level.Info(logger).Log("listener", "socket_writes", "addr", *sockAddr)
+			level.Info(logger).Log("listener", "socket_writes", "network", socketLn.Addr().Network(), "address", socketLn.Addr().String())
 			return forwardFunc()
 		}, func(error) {
 			forwardClose()
 		})
 	}
 	{
 		mux := http.NewServeMux()
-		mux.Handle(promPath, u)
+		mux.Handle(metricsPath, u)
+		if declPath != "" {
+			mux.Handle(declPath, declHandler)
+		}
 		server := http.Server{Handler: mux}
 		g.Add(func() error {
-			level.Info(logger).Log("listener", "prometheus_scrapes", "addr", promLn.Addr().String(), "path", promPath)
-			return server.Serve(promLn)
+			keyvals := []interface{}{"listener", "prometheus_scrapes", "network", metricsLn.Addr().Network(), "address", metricsLn.Addr().String(), "path", metricsPath}
+			if declPath != "" {
+				keyvals = append(keyvals, "declarations", declPath)
+			}
+			level.Info(logger).Log(keyvals...)
+			return server.Serve(metricsLn)
 		}, func(error) {
 			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
 			defer cancel()

universe.go

@@ -32,7 +32,8 @@ type (
 		values  map[timeseriesKey]timeseriesValue
 	}
 
-	// timeseriesKey is universally unique e.g. `http_requests_total{method="GET",status_code="200"}`.
+	// timeseriesKey is universally unique, e.g.
+	// `http_requests_total{method="GET",status_code="200"}`.
 	timeseriesKey string
 
 	// timeseriesValue is a set of observations for
@@ -192,8 +193,13 @@ type observation struct {
 	Value   *float64          `json:"value,omitempty"`
 }
 
-func (o observation) metricName() metricName       { return metricName(o.Name) }
-func (o observation) timeseriesKey() timeseriesKey { return makeTimeseriesKey(o.Name, o.Labels) }
+func (o observation) metricName() metricName {
+	return metricName(o.Name)
+}
+
+func (o observation) timeseriesKey() timeseriesKey {
+	return makeTimeseriesKey(o.Name, o.Labels)
+}
 
 //
 //
@@ -215,8 +221,13 @@ func newCounter(o observation) (*counter, error) {
 	}, nil
 }
 
-func (c *counter) metricName() metricName       { return metricName(c.n) }
-func (c *counter) timeseriesKey() timeseriesKey { return makeTimeseriesKey(c.n, c.labels) }
+func (c *counter) metricName() metricName {
+	return metricName(c.n)
+}
+
+func (c *counter) timeseriesKey() timeseriesKey {
+	return makeTimeseriesKey(c.n, c.labels)
+}
 
 func (c *counter) observe(o observation) error {
 	if o.Value == nil {
@@ -253,8 +264,13 @@ func newGauge(o observation) (*gauge, error) {
 	}, nil
 }
 
-func (g *gauge) metricName() metricName       { return metricName(g.n) }
-func (g *gauge) timeseriesKey() timeseriesKey { return makeTimeseriesKey(g.n, g.labels) }
+func (g *gauge) metricName() metricName {
+	return metricName(g.n)
+}
+
+func (g *gauge) timeseriesKey() timeseriesKey {
+	return makeTimeseriesKey(g.n, g.labels)
+}
 
 func (g *gauge) observe(o observation) error {
 	if o.Value == nil {
@@ -307,8 +323,13 @@ func newHistogram(o observation) (*histogram, error) {
 	}, nil
 }
 
-func (h *histogram) metricName() metricName       { return metricName(h.n) }
-func (h *histogram) timeseriesKey() timeseriesKey { return makeTimeseriesKey(h.n, h.labels) }
+func (h *histogram) metricName() metricName {
+	return metricName(h.n)
+}
+
+func (h *histogram) timeseriesKey() timeseriesKey {
+	return makeTimeseriesKey(h.n, h.labels)
+}
 
 func (h *histogram) observe(o observation) error {
 	if o.Value == nil {