From 53ad91c63c2788a83d0e80985ffa89ce7cdf203f Mon Sep 17 00:00:00 2001
From: Rasmus Dahlberg <rasmus.dahlberg@kau.se>
Date: Wed, 4 Nov 2020 23:09:42 +0100
Subject: added prometheus metrics

---
 handler.go     | 14 +++++++++++++-
 instance.go    |  5 +++++
 metric.go      | 28 ++++++++++++++++++++++++++++
 server/main.go |  4 ++++
 4 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 metric.go

diff --git a/handler.go b/handler.go
index 735d798..e45a78f 100644
--- a/handler.go
+++ b/handler.go
@@ -21,7 +21,16 @@ type appHandler struct {
 }
 
 func (a appHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	ctx, cancel := context.WithDeadline(r.Context(), time.Now().Add(a.instance.Deadline))
+	// export prometheus metrics
+	var now time.Time = time.Now()
+	var statusCode int
+	defer func() {
+		rspcnt.Inc(a.instance.LogParameters.id(), a.endpoint, fmt.Sprintf("%d", statusCode))
+		latency.Observe(time.Now().Sub(now).Seconds(), a.instance.LogParameters.id(), a.endpoint, fmt.Sprintf("%d", statusCode))
+	}()
+	reqcnt.Inc(a.instance.LogParameters.id(), a.endpoint)
+
+	ctx, cancel := context.WithDeadline(r.Context(), now.Add(a.instance.Deadline))
 	defer cancel()
 
 	if r.Method != a.method {
@@ -71,6 +80,7 @@ func addEntry(ctx context.Context, i *Instance, w http.ResponseWriter, r *http.R
 	if err != nil {
 		return http.StatusInternalServerError, err
 	}
+	lastSdiTimestamp.Set(float64(time.Now().Unix()), i.LogParameters.id())
 	if err := WriteJsonResponse(rsp, w); err != nil {
 		return http.StatusInternalServerError, err
 	}
@@ -207,6 +217,8 @@ func getSth(ctx context.Context, i *Instance, w http.ResponseWriter, _ *http.Req
 	if err != nil {
 		return http.StatusInternalServerError, err
 	}
+	lastSthTimestamp.Set(float64(time.Now().Unix()), i.LogParameters.id())
+	lastSthSize.Set(float64(sth.SignedTreeHeadV1.TreeHead.TreeSize), i.LogParameters.id())
 	if err := WriteJsonResponse(rsp, w); err != nil {
 		return http.StatusInternalServerError, err
 	}
diff --git a/instance.go b/instance.go
index 843e9f8..65ebcb3 100644
--- a/instance.go
+++ b/instance.go
@@ -43,6 +43,10 @@ func (p LogParameters) String() string {
 	return fmt.Sprintf("LogId(%s) TreeId(%d) Prefix(%s) NumAnchors(%d)", base64.StdEncoding.EncodeToString(p.LogId), p.TreeId, p.Prefix, len(p.AnchorList))
 }
 
+func (i *LogParameters) id() string {
+	return base64.StdEncoding.EncodeToString(i.LogId)
+}
+
 // NewInstance returns a new STFE Instance
 func NewInstance(lp *LogParameters, client trillian.TrillianLogClient, deadline time.Duration, mux *http.ServeMux) (*Instance, error) {
 	i := &Instance{
@@ -51,6 +55,7 @@ func NewInstance(lp *LogParameters, client trillian.TrillianLogClient, deadline
 		Deadline:      deadline,
 	}
 	i.registerHandlers(mux)
+	once.Do(metricSetup)
 	return i, nil
 }
 
diff --git a/metric.go b/metric.go
new file mode 100644
index 0000000..7179458
--- /dev/null
+++ b/metric.go
@@ -0,0 +1,28 @@
+package stfe
+
+import (
+	"sync"
+
+	"github.com/google/trillian/monitoring"
+	"github.com/google/trillian/monitoring/prometheus"
+)
+
+var (
+	once             sync.Once
+	reqcnt           monitoring.Counter   // number of incoming http requests
+	rspcnt           monitoring.Counter   // number of valid http responses
+	latency          monitoring.Histogram // request-response latency
+	lastSdiTimestamp monitoring.Gauge     // unix timestamp from the most recent sdi
+	lastSthTimestamp monitoring.Gauge     // unix timestamp from the most recent sth
+	lastSthSize      monitoring.Gauge     // tree size of most recent sth
+)
+
+func metricSetup() {
+	mf := prometheus.MetricFactory{}
+	reqcnt = mf.NewCounter("http_req", "number of http requests", "logid", "endpoint")
+	rspcnt = mf.NewCounter("http_rsp", "number of http requests", "logid", "endpoint", "status")
+	latency = mf.NewHistogram("http_latency", "http request-response latency", "logid", "endpoint", "status")
+	lastSthTimestamp = mf.NewGauge("last_sth_timestamp", "unix timestamp while handling the most recent sth", "logid")
+	lastSdiTimestamp = mf.NewGauge("last_sdi_timestamp", "unix timestamp while handling the most recent sdi", "logid")
+	lastSthSize = mf.NewGauge("last_sth_size", "most recent sth tree size", "logid")
+}
diff --git a/server/main.go b/server/main.go
index aea2239..7cf9ccf 100644
--- a/server/main.go
+++ b/server/main.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/golang/glog"
 	"github.com/google/trillian"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/system-transparency/stfe"
 	"google.golang.org/grpc"
 )
@@ -40,6 +41,9 @@ func main() {
 	mux := http.NewServeMux()
 	http.Handle("/", mux)
 
+	glog.Info("Adding prometheus handler on path: /metrics")
+	http.Handle("/metrics", promhttp.Handler())
+
 	lp, err := stfe.NewLogParameters(*trillianID, *prefix, *anchorPath, *keyPath, *maxRange, *maxChain)
 	if err != nil {
 		glog.Fatalf("failed setting up log parameters: %v", err)
-- 
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