140 lines
4.7 KiB
Markdown
140 lines
4.7 KiB
Markdown
# khatru, a relay framework [](https://pkg.go.dev/github.com/fiatjaf/khatru#Relay)
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[](https://github.com/fiatjaf/khatru/actions/workflows/test.yml)
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[](https://pkg.go.dev/github.com/fiatjaf/khatru)
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[](https://goreportcard.com/report/github.com/fiatjaf/khatru)
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Khatru makes it easy to write very very custom relays:
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- custom event or filter acceptance policies
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- custom `AUTH` handlers
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- custom storage and pluggable databases
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- custom webpages and other HTTP handlers
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Here's a sample:
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```go
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package main
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import (
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"context"
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"fmt"
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"log"
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"net/http"
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"github.com/fiatjaf/khatru"
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"github.com/nbd-wtf/go-nostr"
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)
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func main() {
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// create the relay instance
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relay := khatru.NewRelay()
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// set up some basic properties (will be returned on the NIP-11 endpoint)
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relay.Info.Name = "my relay"
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relay.Info.PubKey = "79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798"
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relay.Info.Description = "this is my custom relay"
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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"
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// you must bring your own storage scheme -- if you want to have any
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store := make(map[string]*nostr.Event, 120)
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// set up the basic relay functions
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relay.StoreEvent = append(relay.StoreEvent,
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func(ctx context.Context, event *nostr.Event) error {
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store[event.ID] = event
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return nil
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},
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)
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relay.QueryEvents = append(relay.QueryEvents,
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func(ctx context.Context, filter nostr.Filter) (chan *nostr.Event, error) {
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ch := make(chan *nostr.Event)
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go func() {
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for _, evt := range store {
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if filter.Matches(evt) {
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ch <- evt
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}
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}
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close(ch)
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}()
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return ch, nil
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},
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)
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relay.DeleteEvent = append(relay.DeleteEvent,
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func(ctx context.Context, event *nostr.Event) error {
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delete(store, event.ID)
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return nil
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},
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)
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// there are many other configurable things you can set
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relay.RejectEvent = append(relay.RejectEvent,
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// built-in policies
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policies.ValidateKind,
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// define your own policies
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policies.PreventLargeTags(100),
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func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
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if event.PubKey == "fa984bd7dbb282f07e16e7ae87b26a2a7b9b90b7246a44771f0cf5ae58018f52" {
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return true, "we don't allow this person to write here"
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}
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return false, "" // anyone else can
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},
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)
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// you can request auth by rejecting an event or a request with the prefix "auth-required: "
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relay.RejectFilter = append(relay.RejectFilter,
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// built-in policies
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policies.NoComplexFilters,
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// define your own policies
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func(ctx context.Context, filter nostr.Filter) (reject bool, msg string) {
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if pubkey := khatru.GetAuthed(ctx); pubkey != "" {
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log.Printf("request from %s\n", pubkey)
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return false, ""
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}
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return true, "auth-required: only authenticated users can read from this relay"
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// (this will cause an AUTH message to be sent and then a CLOSED message such that clients can
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// authenticate and then request again)
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},
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)
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// check the docs for more goodies!
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mux := relay.Router()
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// set up other http handlers
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mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("content-type", "text/html")
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fmt.Fprintf(w, `<b>welcome</b> to my relay!`)
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})
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// start the server
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fmt.Println("running on :3334")
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http.ListenAndServe(":3334", relay)
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}
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```
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### But I don't want to write my own database!
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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](https://pkg.go.dev/github.com/fiatjaf/eventstore/sqlite3):
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```go
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db := sqlite3.SQLite3Backend{DatabaseURL: "/tmp/khatru-sqlite-tmp"}
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if err := db.Init(); err != nil {
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panic(err)
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}
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relay.StoreEvent = append(relay.StoreEvent, db.SaveEvent)
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relay.QueryEvents = append(relay.QueryEvents, db.QueryEvents)
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relay.CountEvents = append(relay.CountEvents, db.CountEvents)
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relay.DeleteEvent = append(relay.DeleteEvent, db.DeleteEvent)
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```
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### But I don't want to write a bunch of custom policies!
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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:
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```go
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policies.ApplySaneDefaults(relay)
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```
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Contributions to this are very much welcomed.
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