Re-add some simple example binaries.

I intentionally left out the Makefile infrastructure that we had
previously for this, as it's not strictly needed and adds
complexity/maintenance burden.

examples/random/main.go

@@ -0,0 +1,70 @@
+// Copyright 2015 Prometheus Team
+// 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.
+
+// A simple example exposing fictional RPC latencies with different types of
+// random distributions (uniform, normal, and exponential) as Prometheus
+// metrics.
+package main
+
+import (
+	"flag"
+	"math/rand"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	addr          = flag.String("listen-address", ":8080", "The address to listen on for HTTP requests.")
+	uniformDomain = flag.Float64("random.uniform.domain", 200, "The domain for the uniform distribution.")
+	normDomain    = flag.Float64("random.exponential.domain", 200, "The domain for the normal distribution.")
+	normMean      = flag.Float64("random.exponential.mean", 10, "The mean for the normal distribution.")
+)
+
+var (
+	// Create a summary to track fictional interservice RPC latencies for three
+	// distinct services with different latency distributions. These services are
+	// differentiated via a "service" label.
+	rpcDurations = prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Name: "rpc_durations_microseconds",
+			Help: "RPC latency distributions.",
+		},
+		[]string{"service"},
+	)
+)
+
+func init() {
+	// Register the summary with Prometheus's default registry.
+	prometheus.MustRegister(rpcDurations)
+}
+
+func main() {
+	flag.Parse()
+
+	go func() {
+		for {
+			// Periodically record some sample latencies for the three services.
+			rpcDurations.WithLabelValues("uniform").Observe(rand.Float64() * *uniformDomain)
+			rpcDurations.WithLabelValues("normal").Observe((rand.NormFloat64() * *normDomain) + *normMean)
+			rpcDurations.WithLabelValues("exponential").Observe(rand.ExpFloat64())
+
+			time.Sleep(100 * time.Millisecond)
+		}
+	}()
+
+	// Expose the registered metrics via HTTP.
+	http.Handle("/metrics", prometheus.Handler())
+	http.ListenAndServe(*addr, nil)
+}

examples/simple/main.go

@@ -0,0 +1,30 @@
+// Copyright 2015 Prometheus Team
+// 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.
+
+// A minimal example of how to include Prometheus instrumentation.
+package main
+
+import (
+	"flag"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var addr = flag.String("listen-address", ":8080", "The address to listen on for HTTP requests.")
+
+func main() {
+	flag.Parse()
+	http.Handle("/metrics", prometheus.Handler())
+	http.ListenAndServe(*addr, nil)
+}