feat: ipns max cache ttl (#91)

* feat: ipns max cache ttl

* docs: clarify TTL cap also applies to DNSLink

* docs: clarify default respects original TTL

---------

Co-authored-by: Marcin Rataj <lidel@lidel.org>

docs/environment-variables.md

@@ -8,6 +8,7 @@
   - [`RAINBOW_TRUSTLESS_GATEWAY_DOMAINS`](#rainbow_trustless_gateway_domains)
   - [`RAINBOW_GC_INTERVAL`](#rainbow_gc_interval)
   - [`RAINBOW_GC_THRESHOLD`](#rainbow_gc_threshold)
+  - [`RAINBOW_IPNS_MAX_CACHE_TTL`](#rainbow_ipns_max_cache_ttl)
   - [`KUBO_RPC_URL`](#kubo_rpc_url)
 - [Logging](#logging)
   - [`GOLOG_LOG_LEVEL`](#golog_log_level)
@@ -67,7 +68,6 @@ Default: none (`Host` is ignored and gateway at `127.0.0.1` supports both deseri
 
 The interval at which the garbage collector will be called. This is given as a string that corresponds to the duration of the interval. Set 0 to disable.
 
-
 Default: `60m`
 
 ## `RAINBOW_GC_THRESHOLD`
@@ -78,6 +78,19 @@ When the periodic GC runs, it checks for the total and available space on disk.
 
 Default: `0.3` (always keep 30% of the disk available)
 
+## `RAINBOW_IPNS_MAX_CACHE_TTL`
+
+When set, it defines the upper bound limit (in ms) of how long a `/ipns/{id}`
+lookup result will be cached and read from cache before checking for updates.
+
+The limit is applied to everything under the `/ipns/` namespace, and allows to cap both
+the [Time-To-Live (TTL)](https://specs.ipfs.tech/ipns/ipns-record/#ttl-uint64)
+of [IPNS Records](https://specs.ipfs.tech/ipns/ipns-record/)
+and the [TTL of DNS TXT records](https://datatracker.ietf.org/doc/html/rfc2181#section-8)
+with [DNSLink](https://dnslink.dev/).
+
+Default: No upper bound, [TTL from IPNS Record](https://specs.ipfs.tech/ipns/ipns-record/#ttl-uint64) or [TTL from DNSLink](https://datatracker.ietf.org/doc/html/rfc2181#section-8) used as-is.
+
 ### `KUBO_RPC_URL`
 
 Single URL or a comma separated list of RPC endpoints that provide legacy `/api/v0` from Kubo.

main.go

@@ -198,6 +198,12 @@ Generate an identity seed and launch a gateway:
 			EnvVars: []string{"RAINBOW_BLOCKSTORE"},
 			Usage:   "Type of blockstore to use, such as flatfs or badger. See https://github.com/ipfs/rainbow/blockstore.md for more details",
 		},
+		&cli.DurationFlag{
+			Name:    "ipns-max-cache-ttl",
+			Value:   0,
+			EnvVars: []string{"RAINBOW_IPNS_MAX_CACHE_TTL"},
+			Usage:   "Optional cap on caching duration for IPNS/DNSLink lookups. Set to 0 to respect original TTLs.",
+		},
 	}
 
 	app.Commands = []*cli.Command{
@@ -296,6 +302,7 @@ share the same seed as long as the indexes are different.
 			RoutingV1:               cctx.String("routing"),
 			KuboRPCURLs:             getEnvs(EnvKuboRPC, DefaultKuboRPC),
 			DHTSharedHost:           cctx.Bool("dht-shared-host"),
+			IpnsMaxCacheTTL:         cctx.Duration("ipns-max-cache-ttl"),
 			DenylistSubs:            getCommaSeparatedList(cctx.String("denylists")),
 			Peering:                 peeringAddrs,
 			GCInterval:              cctx.Duration("gc-interval"),

setup.go

@@ -101,6 +101,7 @@ type Config struct {
 	RoutingV1               string
 	KuboRPCURLs             []string
 	DHTSharedHost           bool
+	IpnsMaxCacheTTL         time.Duration
 
 	DenylistSubs []string
 	Peering      []peer.AddrInfo
@@ -346,7 +347,11 @@ func Setup(ctx context.Context, cfg Config, key crypto.PrivKey, dnsCache *cached
 	if err != nil {
 		return nil, err
 	}
-	ns, err := namesys.NewNameSystem(vs, namesys.WithDNSResolver(dns))
+	nsOptions := []namesys.Option{namesys.WithDNSResolver(dns)}
+	if cfg.IpnsMaxCacheTTL > 0 {
+		nsOptions = append(nsOptions, namesys.WithMaxCacheTTL(cfg.IpnsMaxCacheTTL))
+	}
+	ns, err := namesys.NewNameSystem(vs, nsOptions...)
 	if err != nil {
 		return nil, err
 	}