status-im/status-go

package datasync

import (
    "errors"
    "math"
    "math/rand"
    "time"

    "github.com/status-im/mvds/protobuf"
    "github.com/status-im/mvds/state"
    "github.com/status-im/mvds/transport"
    "go.uber.org/zap"
)

const backoffInterval = 30

var errNotInitialized = errors.New("datasync transport not initialized")
var DatasyncTicker = 300 * time.Millisecond

// It's easier to calculate nextEpoch if we consider seconds as a unit rather than
// 300 ms, so we multiply the result by the ratio
var offsetToSecond = uint64(time.Second / DatasyncTicker)

type NodeTransport struct {
    packets  chan transport.Packet
    logger   *zap.Logger
    dispatch func(state.PeerID, *protobuf.Payload) error
}

func NewNodeTransport() *NodeTransport {
    return &NodeTransport{
        packets: make(chan transport.Packet),
    }
}

func (t *NodeTransport) Init(dispatch func(state.PeerID, *protobuf.Payload) error, logger *zap.Logger) {
    t.dispatch = dispatch
    t.logger = logger
}

func (t *NodeTransport) AddPacket(p transport.Packet) {
    t.packets <- p
}

func (t *NodeTransport) Watch() transport.Packet {
    return <-t.packets
}

func (t *NodeTransport) Send(_ state.PeerID, peer state.PeerID, payload *protobuf.Payload) error {
    if t.dispatch == nil {
        return errNotInitialized
    }

    // We don't return an error otherwise datasync will keep
    // re-trying sending at each epoch
    err := t.dispatch(peer, payload)
    if err != nil {
        t.logger.Error("failed to send message", zap.Error(err))
        return nil
    }

    return nil
}

// CalculateSendTime calculates the next epoch
// at which a message should be sent.
// We randomize it a bit so that not all messages are sent on the same epoch
func CalculateSendTime(count uint64, time int64) int64 {
    return time + int64(uint64(math.Exp2(float64(count-1)))*backoffInterval*offsetToSecond) + int64(rand.Intn(30)) // nolint: gosec
}