cache: Support redis

Closes: https://todo.xenrox.net/~xenrox/ntfy-alertmanager/11

README.md

@@ -96,12 +96,16 @@ alertmanager {
 # When the alert-mode is set to single, ntfy-alertmanager will cache each single alert
 # to avoid sending recurrences.
 cache {
-    # The type of cache that will be used (default is memory).
+    # The type of cache that will be used (either memory or redis; default is memory).
     type memory
     # How long messages stay in the cache for
     duration 24h
+
+    # Memory cache settings
     # Interval in which the cache is cleaned up
     cleanup-interval 1h
+
+    # Redis cache settings
 }
 ```
 

cache/cache.go

@@ -3,7 +3,7 @@ package cache
 
 // Cache is the interface that describes a cache for ntfy-alertmanager.
 type Cache interface {
-	Set(fingerprint string, status string)
+	Set(fingerprint string, status string) error
-	Contains(fingerprint string, status string) bool
+	Contains(fingerprint string, status string) (bool, error)
 	Cleanup()
 }

cache/memory.go

@@ -27,7 +27,7 @@ func NewMemoryCache(d time.Duration) Cache {
 }
 
 // Set saves an alert in the cache.
-func (c *MemoryCache) Set(fingerprint string, status string) {
+func (c *MemoryCache) Set(fingerprint string, status string) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	alert := new(cachedAlert)
@@ -35,19 +35,20 @@ func (c *MemoryCache) Set(fingerprint string, status string) {
 	alert.status = status
 
 	c.alerts[fingerprint] = alert
+	return nil
 }
 
 // Contains checks if an alert with a given fingerprint is in the cache
-// and checks if the status matches.
+// and if the status matches.
-func (c *MemoryCache) Contains(fingerprint string, status string) bool {
+func (c *MemoryCache) Contains(fingerprint string, status string) (bool, error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	alert, ok := c.alerts[fingerprint]
 	if ok {
-		return alert.status == status
+		return alert.status == status, nil
 	}
 
-	return false
+	return false, nil
 }
 
 func (a *cachedAlert) expired() bool {

cache/redis.go

@@ -0,0 +1,51 @@
+package cache
+
+import (
+	"context"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// RedisCache is the redis cache.
+type RedisCache struct {
+	client   *redis.Client
+	duration time.Duration
+}
+
+// NewRedisCache creates a new redis cache/client.
+func NewRedisCache(redisURL string, d time.Duration) (Cache, error) {
+	c := new(RedisCache)
+	ropts, err := redis.ParseURL(redisURL)
+	if err != nil {
+		return nil, err
+	}
+
+	rdb := redis.NewClient(ropts)
+	c.client = rdb
+	c.duration = d
+
+	return c, nil
+}
+
+// Set saves an alert in the cache.
+func (c *RedisCache) Set(fingerprint string, status string) error {
+	return c.client.SetEx(context.Background(), fingerprint, status, c.duration).Err()
+}
+
+// Contains checks if an alert with a given fingerprint is in the cache
+// and if the status matches.
+func (c *RedisCache) Contains(fingerprint string, status string) (bool, error) {
+	val, err := c.client.Get(context.Background(), fingerprint).Result()
+	if err == redis.Nil {
+		return false, nil
+	} else if err != nil {
+		return false, err
+	}
+
+	return val == status, nil
+}
+
+// Cleanup is an empty function that is simply here to implement the interface.
+// Redis does its own cleanup.
+func (c *RedisCache) Cleanup() {}

config.go

@@ -20,6 +20,7 @@ type cacheType int
 
 const (
 	memory cacheType = iota
+	redis
 )
 
 type config struct {
@@ -256,6 +257,8 @@ func readConfig(path string) (*config, error) {
 			switch strings.ToLower(cacheType) {
 			case "memory":
 				config.cache.Type = memory
+			case "redis":
+				config.cache.Type = redis
 			default:
 				return nil, fmt.Errorf("cache: illegal type %q", cacheType)
 			}

config_test.go

@@ -54,6 +54,7 @@ alertmanager {
 }
 
 cache {
+    type redis
     duration 48h
 }
 `
@@ -73,7 +74,11 @@ cache {
 				"instance:example.com": {Tags: []string{"computer", "example"}},
 			},
 		},
-		cache: cacheConfig{CleanupInterval: time.Hour, Duration: 48 * time.Hour},
+		cache: cacheConfig{
+			Type:            redis,
+			CleanupInterval: time.Hour,
+			Duration:        48 * time.Hour,
+		},
 		am: alertmanagerConfig{
 			SilenceDuration: time.Hour * 24,
 			User:            "user",

go.mod

@@ -5,7 +5,12 @@ go 1.19
 require (
 	git.sr.ht/~emersion/go-scfg v0.0.0-20211215104734-c2c7a15d6c99
 	git.xenrox.net/~xenrox/go-log v0.0.0-20221012231312-9e7356c29b74
+	github.com/redis/go-redis/v9 v9.0.2
 	golang.org/x/text v0.7.0
 )
 
-require github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
+require (
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
+)

go.sum

@@ -2,9 +2,20 @@ git.sr.ht/~emersion/go-scfg v0.0.0-20211215104734-c2c7a15d6c99 h1:1s8n5uisqkR+Bz
 git.sr.ht/~emersion/go-scfg v0.0.0-20211215104734-c2c7a15d6c99/go.mod h1:t+Ww6SR24yYnXzEWiNlOY0AFo5E9B73X++10lrSpp4U=
 git.xenrox.net/~xenrox/go-log v0.0.0-20221012231312-9e7356c29b74 h1:t/52xLRU4IHd2O1nkb9fcUE6K95/KdBtdQYHT31szps=
 git.xenrox.net/~xenrox/go-log v0.0.0-20221012231312-9e7356c29b74/go.mod h1:d98WFDHGpxaEThKue5CfGtr9OrWgbaApprt3GH+OM4s=
+github.com/bsm/ginkgo/v2 v2.5.0 h1:aOAnND1T40wEdAtkGSkvSICWeQ8L3UASX7YVCqQx+eQ=
+github.com/bsm/gomega v1.20.0 h1:JhAwLmtRzXFTx2AkALSLa8ijZafntmhSoU63Ok18Uq8=
+github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/redis/go-redis/v9 v9.0.2 h1:BA426Zqe/7r56kCcvxYLWe1mkaz71LKF77GwgFzSxfE=
+github.com/redis/go-redis/v9 v9.0.2/go.mod h1:/xDTe9EF1LM61hek62Poq2nzQSGj0xSrEtEHbBQevps=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 golang.org/x/text v0.7.0 h1:4BRB4x83lYWy72KwLD/qYDuTu7q9PjSagHvijDw7cLo=
 golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

main.go

@@ -59,8 +59,12 @@ type notification struct {
 func (br *bridge) singleAlertNotifications(p *payload) []*notification {
 	var notifications []*notification
 	for _, alert := range p.Alerts {
-		if br.cache.Contains(alert.Fingerprint, alert.Status) {
+		contains, err := br.cache.Contains(alert.Fingerprint, alert.Status)
-			br.logger.Debugf("Alert %s skipped: Still in cache", alert.Fingerprint)
+		if err != nil {
+			br.logger.Errorf("Failed to lookup alert %q in cache: %v", alert.Fingerprint, err)
+		}
+		if contains {
+			br.logger.Debugf("Alert %q skipped: Still in cache", alert.Fingerprint)
 			continue
 		}
 
@@ -324,7 +328,9 @@ func (br *bridge) handleWebhooks(w http.ResponseWriter, r *http.Request) {
 			if err != nil {
 				br.logger.Errorf("Failed to publish notification: %v", err)
 			} else {
-				br.cache.Set(n.fingerprint, n.status)
+				if err := br.cache.Set(n.fingerprint, n.status); err != nil {
+					br.logger.Errorf("Failed to set alert %q in cache: %v", n.fingerprint, err)
+				}
 			}
 		}
 	} else {
@@ -395,7 +401,18 @@ func main() {
 
 	client := &httpClient{&http.Client{Timeout: time.Second * 3}}
 
-	c := cache.NewMemoryCache(cfg.cache.Duration)
+	var c cache.Cache
+	switch cfg.cache.Type {
+	case memory:
+		c = cache.NewMemoryCache(cfg.cache.Duration)
+	case redis:
+		var err error
+		// TODO: Read URL from config
+		c, err = cache.NewRedisCache("redis://localhost:6379", cfg.cache.Duration)
+		if err != nil {
+			logger.Fatalf("Failed to create redis cache: %v", err)
+		}
+	}
 	bridge := &bridge{cfg: cfg, logger: logger, cache: c, client: client}
 
 	logger.Infof("Listening on %s, ntfy-alertmanager %s", cfg.HTTPAddress, version)
@@ -409,6 +426,8 @@ func main() {
 		http.HandleFunc("/silences", bridge.handleSilences)
 	}
 
-	go bridge.runCleanup()
+	if cfg.cache.Type == memory {
+		go bridge.runCleanup()
+	}
 	logger.Fatal(http.ListenAndServe(cfg.HTTPAddress, nil))
 }