package pubsub import ( "fmt" "github.com/libp2p/go-libp2p/core/peer" ) // NewMessageCache creates a sliding window cache that remembers messages for as // long as `history` slots. // // When queried for messages to advertise, the cache only returns messages in // the last `gossip` slots. // // The `gossip` parameter must be smaller or equal to `history`, or this // function will panic. // // The slack between `gossip` and `history` accounts for the reaction time // between when a message is advertised via IHAVE gossip, and the peer pulls it // via an IWANT command. func NewMessageCache(gossip, history int) *MessageCache { if gossip > history { err := fmt.Errorf("invalid parameters for message cache; gossip slots (%d) cannot be larger than history slots (%d)", gossip, history) panic(err) } return &MessageCache{ msgs: make(map[string]*Message), peertx: make(map[string]map[peer.ID]int), history: make([][]CacheEntry, history), gossip: gossip, msgID: func(msg *Message) string { return DefaultMsgIdFn(msg.Message) }, } } type MessageCache struct { msgs map[string]*Message peertx map[string]map[peer.ID]int history [][]CacheEntry gossip int msgID func(*Message) string } func (mc *MessageCache) SetMsgIdFn(msgID func(*Message) string) { mc.msgID = msgID } type CacheEntry struct { mid string topic string } func (mc *MessageCache) Put(msg *Message) { mid := mc.msgID(msg) mc.msgs[mid] = msg mc.history[0] = append(mc.history[0], CacheEntry{mid: mid, topic: msg.GetTopic()}) } func (mc *MessageCache) Get(mid string) (*Message, bool) { m, ok := mc.msgs[mid] return m, ok } func (mc *MessageCache) GetForPeer(mid string, p peer.ID) (*Message, int, bool) { m, ok := mc.msgs[mid] if !ok { return nil, 0, false } tx, ok := mc.peertx[mid] if !ok { tx = make(map[peer.ID]int) mc.peertx[mid] = tx } tx[p]++ return m, tx[p], true } func (mc *MessageCache) GetGossipIDs(topic string) []string { var mids []string for _, entries := range mc.history[:mc.gossip] { for _, entry := range entries { if entry.topic == topic { mids = append(mids, entry.mid) } } } return mids } func (mc *MessageCache) Shift() { last := mc.history[len(mc.history)-1] for _, entry := range last { delete(mc.msgs, entry.mid) delete(mc.peertx, entry.mid) } for i := len(mc.history) - 2; i >= 0; i-- { mc.history[i+1] = mc.history[i] } mc.history[0] = nil }