Merge pull request 'Add in-memory cache' (#5) from feature-in-memory-cache into main, closes #4

Reviewed-on: #5

.woodpecker/golang-test.yml

@@ -0,0 +1,9 @@
+when:
+  - event: push
+
+steps:
+  test:
+    image: golang:1.22-bullseye
+    commands:
+      - go mod download
+      - go test -v ./...

Makefile

@@ -0,0 +1,3 @@
+
+test:
+	go test ./...

cache/cache.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2024 Adora Laura Kalb <adora@lila.network>
+
+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 cache
+
+import (
+	"net/netip"
+	"sync"
+	"time"
+)
+
+var (
+	GlobalScoreCache  *ScoreCache
+	cacheExpiredAfter = 5 * time.Minute
+)
+
+type ServerScore struct {
+	expiresAt time.Time
+	Score     float64
+}
+
+type ScoreCache struct {
+	stop chan struct{}
+
+	mu sync.RWMutex
+
+	scores map[netip.Addr]ServerScore
+}
+
+type CacheMissError struct{}
+
+func (m *CacheMissError) Error() string {
+	return "User is not in cache!"
+}
+
+func newCacheMissError() *CacheMissError {
+	return &CacheMissError{}
+}
+
+func NewScoreCache() *ScoreCache {
+	lc := &ScoreCache{
+		scores: make(map[netip.Addr]ServerScore),
+		stop:   make(chan struct{}),
+	}
+
+	return lc
+}
+
+func (sc *ScoreCache) Add(score float64, ip netip.Addr, ts time.Time) {
+	ssc := ServerScore{Score: score, expiresAt: ts.Add(cacheExpiredAfter)}
+	sc.mu.Lock()
+	sc.scores[ip] = ssc
+	sc.mu.Unlock()
+}
+
+func (lc *ScoreCache) Get(ip netip.Addr) (ServerScore, error) {
+	now := time.Now()
+	lc.mu.RLock()
+
+	cachedScore, ok := lc.scores[ip]
+	if !ok {
+		lc.mu.RUnlock()
+		return ServerScore{}, newCacheMissError()
+	}
+	lc.mu.RUnlock()
+
+	if now.After(cachedScore.expiresAt) {
+		lc.delete(ip)
+		return ServerScore{}, newCacheMissError()
+	}
+
+	return cachedScore, nil
+}
+
+func (lc *ScoreCache) delete(ip netip.Addr) {
+	lc.mu.Lock()
+
+	delete(lc.scores, ip)
+	lc.mu.Unlock()
+}

cache/cache_test.go

@@ -0,0 +1,49 @@
+/*
+Copyright 2024 Adora Laura Kalb <adora@lila.network>
+
+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 cache
+
+import (
+	"net/netip"
+	"testing"
+	"time"
+)
+
+func TestCacheGet(t *testing.T) {
+	const testFloat = 1.23456
+	cache := NewScoreCache()
+	cache.Add(testFloat, netip.MustParseAddr("1.2.3.4"), time.Now().Add(5*time.Minute))
+
+	score, _ := cache.Get(netip.MustParseAddr("1.2.3.4"))
+	if score.Score != testFloat {
+		t.Fatalf("cache.Get(\"1.2.3.4\") = %f, want %f", score.Score, testFloat)
+	}
+}
+
+func TestCacheMiss(t *testing.T) {
+	now := time.Now()
+	const testFloat = 1.23456
+
+	expiredTime := now.Add(-(time.Minute * 10))
+
+	cache := NewScoreCache()
+	cache.Add(testFloat, netip.MustParseAddr("1.2.3.4"), expiredTime)
+
+	_, err := cache.Get(netip.MustParseAddr("1.2.3.4"))
+	if err == nil {
+		t.Fatalf("cache.Get(\"1.2.3.4\") = got nil, want error")
+	}
+}

collector/collector.go

@@ -27,6 +27,7 @@ import (
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
+	"golang.adora.codes/ntppool-exporter/cache"
 	"golang.adora.codes/ntppool-exporter/models"
 )
 
@@ -61,7 +62,24 @@ func (c Collector) Collect(ch chan<- prometheus.Metric) {
 }
 
 func (c Collector) collect(ch chan<- prometheus.Metric, logger log.Logger) {
-	httpError := false
+	score, err := cache.GlobalScoreCache.Get(c.target)
+	if err == nil {
+		level.Debug(logger).Log("msg", "Serving score from cache",
+			"server", c.target.String(), "score", score.Score)
+
+		serverScoreMetric := prometheus.NewDesc("ntppool_server_score",
+			"Shows the server score currently assigned at ntppool.org",
+			nil, nil)
+
+		m1 := prometheus.MustNewConstMetric(serverScoreMetric, prometheus.GaugeValue, score.Score)
+		m1 = prometheus.NewMetricWithTimestamp(time.Now(), m1)
+		ch <- m1
+		return
+	}
+
+	level.Debug(logger).Log("msg", "Cache miss, querying API",
+		"server", c.target.String())
+
 	var serverApiScore float64 = 0
 	const apiEndpoint = "https://www.ntppool.org/scores/"
 	const apiQuery = "/json?limit=1&monitor=24"
@@ -73,7 +91,7 @@ func (c Collector) collect(ch chan<- prometheus.Metric, logger log.Logger) {
 
 	if err != nil {
 		level.Error(logger).Log("msg", "Error sending HTTP request", "url", url, "message", err)
-		httpError = true
+		return
 	}
 	res, err := client.Do(req)
 	if err != nil {
@@ -97,9 +115,11 @@ func (c Collector) collect(ch chan<- prometheus.Metric, logger log.Logger) {
 		return
 	}
 
-	if !httpError {
 	serverApiScore = response.History[0].Score
-	}
+
+	cache.GlobalScoreCache.Add(serverApiScore, c.target, time.Now())
+	level.Debug(logger).Log("msg", "Added score to cache",
+		"server", c.target.String(), "score", score.Score)
 
 	// TODO: Test or delete
 	serverScoreMetric := prometheus.NewDesc("ntppool_server_score",

helpers/helpers.go

@@ -0,0 +1,25 @@
+/*
+Copyright 2024 Adora Laura Kalb <adora@lila.network>
+
+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 helpers
+
+import (
+	"time"
+)
+
+func UnixToTime(i int64) time.Time {
+	return time.Unix(i, 0)
+}

main.go

@@ -33,6 +33,7 @@ import (
 	"github.com/prometheus/common/version"
 	"github.com/prometheus/exporter-toolkit/web"
 	webflag "github.com/prometheus/exporter-toolkit/web/kingpinflag"
+	"golang.adora.codes/ntppool-exporter/cache"
 	"golang.adora.codes/ntppool-exporter/collector"
 )
 
@@ -95,6 +96,8 @@ func main() {
 	kingpin.Parse()
 	logger := promlog.New(promlogConfig)
 
+	cache.GlobalScoreCache = cache.NewScoreCache()
+
 	level.Info(logger).Log("msg", "Starting ntppool_exporter", "version", version.Info())
 	level.Info(logger).Log("build_context", version.BuildContext())
 

models/api_response.go

@@ -34,7 +34,7 @@ type ApiResponse struct {
 }
 
 type ApiResponseHistory struct {
-	Timestamp int     `json:"ts"`
+	TimestampInt int64   `json:"ts"`
 	Step         int     `json:"step"`
 	Score        float64 `json:"score"`
 	MonitorID    int     `json:"monitor_id"`