# Rendezvous Protocol

### Overview

Similar to [status-im/rendezvous](https://github.com/status-im/rendezvous) 
in using a smaller liveness TTL for records (20s), and not using `UNREGISTER 
REQUEST`, due to assuming that the TTL is very low (making it incompatible 
with libp2p original rendezvous spec). This module is intended to be used 
in go-waku as a lightweight mechanism for generalized peer discovery.

Another difference compared to [libp2p/rendezvous](https://github.com/libp2p/specs/blob/master/rendezvous/README.md) and status-im/rendezvous is the usage of [routing records](https://github.com/libp2p/specs/blob/master/RFC/0003-routing-records.md) and [signed envelopes](https://github.com/libp2p/specs/blob/master/RFC/0002-signed-envelopes.md)

**Protocol identifier**: `/vac/waku/rendezvous/0.0.1`

### Usage

**Adding discovery to gossipsub**
```go
import (
  "github.com/libp2p/go-libp2p"
  "github.com/libp2p/go-libp2p-core/host"
  "github.com/libp2p/go-libp2p-core/peer"
  pubsub "github.com/status-im/go-libp2p-pubsub"
  rendezvous "github.com/status-im/go-waku-rendezvous"
)

// create a new libp2p Host that listens on a random TCP port
h, err := libp2p.New(libp2p.ListenAddrStrings("/ip4/0.0.0.0/tcp/0"))
if err != nil {
  panic(err)
}

// Create a rendezvous instance
rendezvous := rendezvous.NewRendezvousDiscovery(h)

// create a new PubSub service using the GossipSub router
ps, err := pubsub.NewGossipSub(ctx, h, pubsub.WithDiscovery(rendezvous))
if err != nil {
  panic(err)
}
```

**Creating a rendezvous server**
```go
import (
  "database/sql"
  "github.com/syndtr/goleveldb/leveldb"
  "github.com/syndtr/goleveldb/leveldb/opt"
  "github.com/syndtr/goleveldb/leveldb/util"
  "github.com/libp2p/go-libp2p"
  "github.com/libp2p/go-libp2p-core/host"
  "github.com/libp2p/go-libp2p-core/peer"
  pubsub "github.com/status-im/go-libp2p-pubsub"
  rendezvous "github.com/status-im/go-waku-rendezvous"
)

type RendezVousLevelDB struct {
	db *leveldb.DB
}

func NewRendezVousLevelDB(dBPath string) (*RendezVousLevelDB, error) {
	db, err := leveldb.OpenFile(dBPath, &opt.Options{OpenFilesCacheCapacity: 3})

	if err != nil {
		return nil, err
	}

	return &RendezVousLevelDB{db}, nil
}

func (r *RendezVousLevelDB) Delete(key []byte) error {
	return r.db.Delete(key, nil)
}

func (r *RendezVousLevelDB) Put(key []byte, value []byte) error {
	return r.db.Put(key, value, nil)
}

func (r *RendezVousLevelDB) NewIterator(prefix []byte) rendezvous.Iterator {
	return r.db.NewIterator(util.BytesPrefix(prefix), nil)
}


// create a new libp2p Host that listens on a random TCP port
h, err := libp2p.New(libp2p.ListenAddrStrings("/ip4/0.0.0.0/tcp/0"))
if err != nil {
  panic(err)
}

// LevelDB storage for peer records
db, err := NewRendezVousLevelDB("/tmp/rendezvous")
if err != nil {
  panic(err)
}
storage := rendezvous.NewStorage(db)

rendezvousService = rendezvous.NewRendezvousService(h, storage)
if err := rendezvousService.Start(); err != nil {
  panic(err)
}
```

### Protobuf

- [record.pb.Envelope](https://github.com/libp2p/specs/blob/master/RFC/0002-signed-envelopes.md#wire-format)
- [PeerRecord protobuffer](https://github.com/libp2p/specs/blob/master/RFC/0003-routing-records.md#address-record-format)

```protobuf
message Message {
  enum MessageType {
    REGISTER = 0;
    REGISTER_RESPONSE = 1;
    DISCOVER = 2;
    DISCOVER_RESPONSE = 3;
  }

  enum ResponseStatus {
    OK                  = 0;
    E_INVALID_NAMESPACE = 100;
    E_INVALID_PEER_INFO = 101;
    E_INVALID_TTL       = 102;
    E_NOT_AUTHORIZED    = 200;
    E_INTERNAL_ERROR    = 300;
    E_UNAVAILABLE       = 400;
  }

  message Register {
    string ns = 1;
    record.pb.Envelope peer = 2;
    int64 ttl = 3; // in seconds
  }

  message RegisterResponse {
    ResponseStatus status = 1;
    string statusText = 2;
    int64 ttl = 3;
  }

  message Discover {
    string ns = 1;
    int64 limit = 2;
  }

  message DiscoverResponse {
    repeated Register registrations = 1;
    ResponseStatus status = 3;
    string statusText = 4;
  }

  MessageType type = 1;
  Register register = 2;
  RegisterResponse registerResponse = 3;
  Discover discover = 4;
  DiscoverResponse discoverResponse = 5;
}

```