Getting Started

Download the library:

bash

go get github.com/fiatjaf/khatru

Include the library:

import "github.com/fiatjaf/khatru"

Then in your main() function, instantiate a new Relay:

relay := khatru.NewRelay()

Optionally, set up basic info about the relay that will be returned according to NIP-11:

relay.Info.Name = "my relay"
relay.Info.PubKey = "79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798"
relay.Info.Description = "this is my custom relay"
relay.Info.Icon = "https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fliquipedia.net%2Fcommons%2Fimages%2F3%2F35%2FSCProbe.jpg&f=1&nofb=1&ipt=0cbbfef25bce41da63d910e86c3c343e6c3b9d63194ca9755351bb7c2efa3359&ipo=images"

Now we must set up the basic functions for accepting events and answering queries. We could make our own querying engine from scratch, but we can also use eventstore. In this example we'll use the SQLite adapter:

db := sqlite3.SQLite3Backend{DatabaseURL: "/tmp/khatru-sqlite-tmp"}
if err := db.Init(); err != nil {
	panic(err)
}

relay.StoreEvent = append(relay.StoreEvent, db.SaveEvent)
relay.QueryEvents = append(relay.QueryEvents, db.QueryEvents)
relay.DeleteEvent = append(relay.DeleteEvent, db.DeleteEvent)

These are lists of functions that will be called in order every time an EVENT is received, or a REQ query is received. You can add more than one handler there, you can have a function that reads from some other server, but just in some cases, you can do anything.

The next step is adding some protection, because maybe we don't want to allow anyone to write to our relay. Maybe we want to only allow people that have a pubkey starting with "a", "b" or "c":

relay.RejectEvent = append(relay.RejectEvent, func (ctx context.Context, event *nostr.Event) (reject bool, msg string) {
	firstHexChar := event.PubKey[0:1]
	if firstHexChar == "a" || firstHexChar == "b" || firstHexChar == "c" {
		return false, "" // allow
	}
	return true, "you're not allowed in this shard"
})

We can also make use of some default policies that come bundled with Khatru:

import "github.com/fiatjaf/khatru" // implied

relay.RejectEvent = append(relay.RejectEvent, policies.PreventLargeTags(120), policies.PreventTimestampsInThePast(time.Hour * 2), policies.PreventTimestampsInTheFuture(time.Minute * 30))

There are many other ways to customize the relay behavior. Take a look at the Relay struct docs for more, or see the cookbook.

The last step is actually running the server. Our relay is actually an http.Handler, so it can just be ran directly with http.ListenAndServe() from the standard library:

fmt.Println("running on :3334")
http.ListenAndServe(":3334", relay)

And that's it.

Getting Started ​

Getting Started