Khatru makes it easy to write very very custom relays:
- custom event or filter acceptance policies
- custom
AUTHhandlers - custom storage and pluggable databases
- custom webpages and other HTTP handlers
Here's a sample:
package main
import (
"context"
"fmt"
"log"
"net/http"
"github.com/fiatjaf/khatru"
"github.com/nbd-wtf/go-nostr"
)
func main() {
// create the relay instance
relay := khatru.NewRelay()
// set up some basic properties (will be returned on the NIP-11 endpoint)
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"
// you must bring your own storage scheme -- if you want to have any
store := make(map[string]*nostr.Event, 120)
// set up the basic relay functions
relay.StoreEvent = append(relay.StoreEvent,
func(ctx context.Context, event *nostr.Event) error {
store[event.ID] = event
return nil
},
)
relay.QueryEvents = append(relay.QueryEvents,
func(ctx context.Context, filter nostr.Filter) (chan *nostr.Event, error) {
ch := make(chan *nostr.Event)
go func() {
for _, evt := range store {
if filter.Matches(evt) {
ch <- evt
}
}
close(ch)
}()
return ch, nil
},
)
relay.DeleteEvent = append(relay.DeleteEvent,
func(ctx context.Context, event *nostr.Event) error {
delete(store, event.ID)
return nil
},
)
// there are many other configurable things you can set
relay.RejectEvent = append(relay.RejectEvent,
// built-in policies
policies.ValidateKind,
// define your own policies
policies.PreventLargeTags(100),
func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
if event.PubKey == "fa984bd7dbb282f07e16e7ae87b26a2a7b9b90b7246a44771f0cf5ae58018f52" {
return true, "we don't allow this person to write here"
}
return false, "" // anyone else can
},
)
// you can request auth by rejecting an event or a request with the prefix "auth-required: "
relay.RejectFilter = append(relay.RejectFilter,
// built-in policies
policies.NoComplexFilters,
// define your own policies
func(ctx context.Context, filter nostr.Filter) (reject bool, msg string) {
if pubkey := khatru.GetAuthed(ctx); pubkey != "" {
log.Printf("request from %s\n", pubkey)
return false, ""
}
return true, "auth-required: only authenticated users can read from this relay"
// (this will cause an AUTH message to be sent and then a CLOSED message such that clients can
// authenticate and then request again)
},
)
// check the docs for more goodies!
mux := relay.Router()
// set up other http handlers
mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("content-type", "text/html")
fmt.Fprintf(w, `<b>welcome</b> to my relay!`)
})
// start the server
fmt.Println("running on :3334")
http.ListenAndServe(":3334", relay)
}Fear no more. Using the https://github.com/fiatjaf/eventstore module you get a bunch of compatible databases out of the box and you can just plug them into your relay. For example, sqlite:
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.CountEvents = append(relay.CountEvents, db.CountEvents)
relay.DeleteEvent = append(relay.DeleteEvent, db.DeleteEvent)
relay.ReplaceEvent = append(relay.ReplaceEvent, db.ReplaceEvent)Fear no more. We have a bunch of common policies written in the github.com/fiatjaf/khatru/policies package and also a handpicked selection of base sane defaults, which you can apply with:
policies.ApplySaneDefaults(relay)Contributions to this are very much welcomed.