Fix DNS CacheLifetime (#1926)

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

dendrite-config.yaml

@@ -112,7 +112,7 @@ global:
     # Maximum number of entries to hold in the DNS cache, and
     # for how long those items should be considered valid in seconds.
     cache_size: 256
-    cache_lifetime: 300
+    cache_lifetime: "5m" # 5minutes; see https://pkg.go.dev/time@master#ParseDuration for more
 
 # Configuration for the Appservice API.
 app_service_api:

setup/base.go

@@ -139,15 +139,14 @@ func NewBaseDendrite(cfg *config.Dendrite, componentName string, useHTTPAPIs boo
 
 	var dnsCache *gomatrixserverlib.DNSCache
 	if cfg.Global.DNSCache.Enabled {
-		lifetime := time.Second * cfg.Global.DNSCache.CacheLifetime
 		dnsCache = gomatrixserverlib.NewDNSCache(
 			cfg.Global.DNSCache.CacheSize,
-			lifetime,
+			cfg.Global.DNSCache.CacheLifetime,
 		)
 		logrus.Infof(
 			"DNS cache enabled (size %d, lifetime %s)",
 			cfg.Global.DNSCache.CacheSize,
-			lifetime,
+			cfg.Global.DNSCache.CacheLifetime,
 		)
 	}