package events import ( "context" "math" "sync" "github.com/filecoin-project/lotus/chain/stmgr" "github.com/filecoin-project/go-state-types/abi" "github.com/ipfs/go-cid" "golang.org/x/xerrors" "github.com/filecoin-project/lotus/chain/types" ) const NoTimeout = math.MaxInt64 const NoHeight = abi.ChainEpoch(-1) type triggerID = uint64 // msgH is the block height at which a message was present / event has happened type msgH = abi.ChainEpoch // triggerH is the block height at which the listener will be notified about the // message (msgH+confidence) type triggerH = abi.ChainEpoch type eventData interface{} // EventHandler arguments: // `prevTs` is the previous tipset, eg the "from" tipset for a state change. // `ts` is the event tipset, eg the tipset in which the `msg` is included. // `curH`-`ts.Height` = `confidence` type EventHandler func(ctx context.Context, data eventData, prevTs, ts *types.TipSet, curH abi.ChainEpoch) (more bool, err error) // CheckFunc is used for atomicity guarantees. If the condition the callbacks // wait for has already happened in tipset `ts` // // If `done` is true, timeout won't be triggered // If `more` is false, no messages will be sent to EventHandler (RevertHandler // may still be called) type CheckFunc func(ctx context.Context, ts *types.TipSet) (done bool, more bool, err error) // Keep track of information for an event handler type handlerInfo struct { confidence int timeout abi.ChainEpoch disabled bool // TODO: GC after gcConfidence reached handle EventHandler revert RevertHandler } // When a change occurs, a queuedEvent is created and put into a queue // until the required confidence is reached type queuedEvent struct { trigger triggerID data eventData prevTipset, tipset *types.TipSet called bool } // Manages chain head change events, which may be forward (new tipset added to // chain) or backward (chain branch discarded in favour of heavier branch) type hcEvents struct { cs EventAPI lk sync.Mutex lastTs *types.TipSet ctr triggerID // TODO: get rid of trigger IDs and just use pointers as keys. triggers map[triggerID]*handlerInfo // TODO: instead of scheduling events in the future, look at the chain in the past. We can sip the "confidence" queue entirely. // maps block heights to events // [triggerH][msgH][event] confQueue map[triggerH]map[msgH][]*queuedEvent // [msgH][triggerH] revertQueue map[msgH][]triggerH // [timeoutH+confidence][triggerID]{calls} timeouts map[abi.ChainEpoch]map[triggerID]int messageEvents watcherEvents } func newHCEvents(api EventAPI, obs *observer) *hcEvents { e := &hcEvents{ cs: api, confQueue: map[triggerH]map[msgH][]*queuedEvent{}, revertQueue: map[msgH][]triggerH{}, triggers: map[triggerID]*handlerInfo{}, timeouts: map[abi.ChainEpoch]map[triggerID]int{}, } e.messageEvents = newMessageEvents(e, api) e.watcherEvents = newWatcherEvents(e, api) // We need to take the lock as the observer could immediately try calling us. e.lk.Lock() e.lastTs = obs.Observe((*hcEventsObserver)(e)) e.lk.Unlock() return e } type hcEventsObserver hcEvents func (e *hcEventsObserver) Apply(ctx context.Context, from, to *types.TipSet) error { e.lk.Lock() defer e.lk.Unlock() defer func() { e.lastTs = to }() // Check if the head change caused any state changes that we were // waiting for stateChanges := e.checkStateChanges(from, to) // Queue up calls until there have been enough blocks to reach // confidence on the state changes for tid, data := range stateChanges { e.queueForConfidence(tid, data, from, to) } // Check if the head change included any new message calls newCalls := e.checkNewCalls(ctx, from, to) // Queue up calls until there have been enough blocks to reach // confidence on the message calls for tid, calls := range newCalls { for _, data := range calls { e.queueForConfidence(tid, data, nil, to) } } for at := from.Height() + 1; at <= to.Height(); at++ { // Apply any queued events and timeouts that were targeted at the // current chain height e.applyWithConfidence(ctx, at) e.applyTimeouts(ctx, at, to) } return nil } func (e *hcEventsObserver) Revert(ctx context.Context, from, to *types.TipSet) error { e.lk.Lock() defer e.lk.Unlock() defer func() { e.lastTs = to }() reverts, ok := e.revertQueue[from.Height()] if !ok { return nil // nothing to do } for _, triggerH := range reverts { toRevert := e.confQueue[triggerH][from.Height()] for _, event := range toRevert { if !event.called { continue // event wasn't apply()-ied yet } trigger := e.triggers[event.trigger] if err := trigger.revert(ctx, from); err != nil { log.Errorf("reverting chain trigger (@H %d, triggered @ %d) failed: %s", from.Height(), triggerH, err) } } delete(e.confQueue[triggerH], from.Height()) } delete(e.revertQueue, from.Height()) return nil } // Queue up events until the chain has reached a height that reflects the // desired confidence func (e *hcEventsObserver) queueForConfidence(trigID uint64, data eventData, prevTs, ts *types.TipSet) { trigger := e.triggers[trigID] appliedH := ts.Height() triggerH := appliedH + abi.ChainEpoch(trigger.confidence) byOrigH, ok := e.confQueue[triggerH] if !ok { byOrigH = map[abi.ChainEpoch][]*queuedEvent{} e.confQueue[triggerH] = byOrigH } byOrigH[appliedH] = append(byOrigH[appliedH], &queuedEvent{ trigger: trigID, data: data, tipset: ts, prevTipset: prevTs, }) e.revertQueue[appliedH] = append(e.revertQueue[appliedH], triggerH) } // Apply any events that were waiting for this chain height for confidence func (e *hcEventsObserver) applyWithConfidence(ctx context.Context, height abi.ChainEpoch) { byOrigH, ok := e.confQueue[height] if !ok { return // no triggers at this height } for origH, events := range byOrigH { for _, event := range events { if event.called { continue } trigger := e.triggers[event.trigger] if trigger.disabled { continue } more, err := trigger.handle(ctx, event.data, event.prevTipset, event.tipset, height) if err != nil { log.Errorf("chain trigger (@H %d, triggered @ %d) failed: %s", origH, height, err) continue // don't revert failed calls } event.called = true touts, ok := e.timeouts[trigger.timeout] if ok { touts[event.trigger]++ } trigger.disabled = !more } } } // Apply any timeouts that expire at this height func (e *hcEventsObserver) applyTimeouts(ctx context.Context, at abi.ChainEpoch, ts *types.TipSet) { triggers, ok := e.timeouts[at] if !ok { return // nothing to do } for triggerID, calls := range triggers { if calls > 0 { continue // don't timeout if the method was called } trigger := e.triggers[triggerID] if trigger.disabled { continue } // This should be cached. timeoutTs, err := e.cs.ChainGetTipSetAfterHeight(ctx, at-abi.ChainEpoch(trigger.confidence), ts.Key()) if err != nil { log.Errorf("events: applyTimeouts didn't find tipset for event; wanted %d; current %d", at-abi.ChainEpoch(trigger.confidence), at) } more, err := trigger.handle(ctx, nil, nil, timeoutTs, at) if err != nil { log.Errorf("chain trigger (call @H %d, called @ %d) failed: %s", timeoutTs.Height(), at, err) continue // don't revert failed calls } trigger.disabled = !more // allows messages after timeout } } // Listen for an event // - CheckFunc: immediately checks if the event already occurred // - EventHandler: called when the event has occurred, after confidence tipsets // - RevertHandler: called if the chain head changes causing the event to revert // - confidence: wait this many tipsets before calling EventHandler // - timeout: at this chain height, timeout on waiting for this event func (e *hcEvents) onHeadChanged(ctx context.Context, check CheckFunc, hnd EventHandler, rev RevertHandler, confidence int, timeout abi.ChainEpoch) (triggerID, error) { e.lk.Lock() defer e.lk.Unlock() // Check if the event has already occurred done, more, err := check(ctx, e.lastTs) if err != nil { return 0, xerrors.Errorf("called check error (h: %d): %w", e.lastTs.Height(), err) } if done { timeout = NoTimeout } id := e.ctr e.ctr++ e.triggers[id] = &handlerInfo{ confidence: confidence, timeout: timeout + abi.ChainEpoch(confidence), disabled: !more, handle: hnd, revert: rev, } // If there's a timeout, set up a timeout check at that height if timeout != NoTimeout { if e.timeouts[timeout+abi.ChainEpoch(confidence)] == nil { e.timeouts[timeout+abi.ChainEpoch(confidence)] = map[uint64]int{} } e.timeouts[timeout+abi.ChainEpoch(confidence)][id] = 0 } return id, nil } // headChangeAPI is used to allow the composed event APIs to call back to hcEvents // to listen for changes type headChangeAPI interface { onHeadChanged(ctx context.Context, check CheckFunc, hnd EventHandler, rev RevertHandler, confidence int, timeout abi.ChainEpoch) (triggerID, error) } // watcherEvents watches for a state change type watcherEvents struct { cs EventAPI hcAPI headChangeAPI lk sync.RWMutex matchers map[triggerID]StateMatchFunc } func newWatcherEvents(hcAPI headChangeAPI, cs EventAPI) watcherEvents { return watcherEvents{ cs: cs, hcAPI: hcAPI, matchers: make(map[triggerID]StateMatchFunc), } } // Run each of the matchers against the previous and current state to see if // there's a change func (we *watcherEvents) checkStateChanges(oldState, newState *types.TipSet) map[triggerID]eventData { we.lk.RLock() defer we.lk.RUnlock() res := make(map[triggerID]eventData) for tid, matchFn := range we.matchers { ok, data, err := matchFn(oldState, newState) if err != nil { log.Errorf("event diff fn failed: %s", err) continue } if ok { res[tid] = data } } return res } // StateChange represents a change in state type StateChange interface{} // StateChangeHandler arguments: // `oldTs` is the state "from" tipset // `newTs` is the state "to" tipset // `states` is the change in state // `curH`-`ts.Height` = `confidence` type StateChangeHandler func(oldTs, newTs *types.TipSet, states StateChange, curH abi.ChainEpoch) (more bool, err error) type StateMatchFunc func(oldTs, newTs *types.TipSet) (bool, StateChange, error) // StateChanged registers a callback which is triggered when a specified state // change occurs or a timeout is reached. // // * `CheckFunc` callback is invoked immediately with a recent tipset, it // returns two booleans - `done`, and `more`. // // * `done` should be true when some on-chain state change we are waiting // for has happened. When `done` is set to true, timeout trigger is disabled. // // * `more` should be false when we don't want to receive new notifications // through StateChangeHandler. Note that notifications may still be delivered to // RevertHandler // // * `StateChangeHandler` is called when the specified state change was observed // on-chain, and a confidence threshold was reached, or the specified `timeout` // height was reached with no state change observed. When this callback is // invoked on a timeout, `oldTs` and `states are set to nil. // This callback returns a boolean specifying whether further notifications // should be sent, like `more` return param from `CheckFunc` above. // // * `RevertHandler` is called after apply handler, when we drop the tipset // containing the message. The tipset passed as the argument is the tipset // that is being dropped. Note that the event dropped may be re-applied // in a different tipset in small amount of time. // // * `StateMatchFunc` is called against each tipset state. If there is a match, // the state change is queued up until the confidence interval has elapsed (and // `StateChangeHandler` is called) func (we *watcherEvents) StateChanged(check CheckFunc, scHnd StateChangeHandler, rev RevertHandler, confidence int, timeout abi.ChainEpoch, mf StateMatchFunc) error { hnd := func(ctx context.Context, data eventData, prevTs, ts *types.TipSet, height abi.ChainEpoch) (bool, error) { states, ok := data.(StateChange) if data != nil && !ok { panic("expected StateChange") } return scHnd(prevTs, ts, states, height) } id, err := we.hcAPI.onHeadChanged(context.TODO(), check, hnd, rev, confidence, timeout) if err != nil { return err } we.lk.Lock() defer we.lk.Unlock() we.matchers[id] = mf return nil } // messageEvents watches for message calls to actors type messageEvents struct { cs EventAPI hcAPI headChangeAPI lk sync.RWMutex matchers map[triggerID]MsgMatchFunc } func newMessageEvents(hcAPI headChangeAPI, cs EventAPI) messageEvents { return messageEvents{ cs: cs, hcAPI: hcAPI, matchers: make(map[triggerID]MsgMatchFunc), } } // Check if there are any new actor calls func (me *messageEvents) checkNewCalls(ctx context.Context, from, to *types.TipSet) map[triggerID][]eventData { me.lk.RLock() defer me.lk.RUnlock() // For each message in the tipset res := make(map[triggerID][]eventData) me.messagesForTs(from, func(msg *types.Message) { // TODO: provide receipts // Run each trigger's matcher against the message for tid, matchFn := range me.matchers { matched, err := matchFn(msg) if err != nil { log.Errorf("event matcher failed: %s", err) continue } // If there was a match, include the message in the results for the // trigger if matched { res[tid] = append(res[tid], msg) } } }) return res } // Get the messages in a tipset func (me *messageEvents) messagesForTs(ts *types.TipSet, consume func(*types.Message)) { seen := map[cid.Cid]struct{}{} for i, tsb := range ts.Cids() { msgs, err := me.cs.ChainGetBlockMessages(context.TODO(), tsb) if err != nil { log.Errorf("messagesForTs MessagesForBlock failed (ts.H=%d, Bcid:%s, B.Mcid:%s): %s", ts.Height(), tsb, ts.Blocks()[i].Messages, err) continue } for i, c := range msgs.Cids { // We iterate over the CIDs to avoid having to recompute them. _, ok := seen[c] if ok { continue } seen[c] = struct{}{} if i < len(msgs.BlsMessages) { consume(msgs.BlsMessages[i]) } else { consume(&msgs.SecpkMessages[i-len(msgs.BlsMessages)].Message) } } } } // MsgHandler arguments: // `ts` is the tipset, in which the `msg` is included. // `curH`-`ts.Height` = `confidence` type MsgHandler func(msg *types.Message, rec *types.MessageReceipt, ts *types.TipSet, curH abi.ChainEpoch) (more bool, err error) type MsgMatchFunc func(msg *types.Message) (matched bool, err error) // Called registers a callback which is triggered when a specified method is // called on an actor, or a timeout is reached. // // * `CheckFunc` callback is invoked immediately with a recent tipset, it // returns two booleans - `done`, and `more`. // // * `done` should be true when some on-chain action we are waiting for has // happened. When `done` is set to true, timeout trigger is disabled. // // * `more` should be false when we don't want to receive new notifications // through MsgHandler. Note that notifications may still be delivered to // RevertHandler // // * `MsgHandler` is called when the specified event was observed on-chain, // and a confidence threshold was reached, or the specified `timeout` height // was reached with no events observed. When this callback is invoked on a // timeout, `msg` is set to nil. This callback returns a boolean specifying // whether further notifications should be sent, like `more` return param // from `CheckFunc` above. // // * `RevertHandler` is called after apply handler, when we drop the tipset // containing the message. The tipset passed as the argument is the tipset // that is being dropped. Note that the message dropped may be re-applied // in a different tipset in small amount of time. // // * `MsgMatchFunc` is called against each message. If there is a match, the // message is queued up until the confidence interval has elapsed (and // `MsgHandler` is called) func (me *messageEvents) Called(ctx context.Context, check CheckFunc, msgHnd MsgHandler, rev RevertHandler, confidence int, timeout abi.ChainEpoch, mf MsgMatchFunc) error { hnd := func(ctx context.Context, data eventData, prevTs, ts *types.TipSet, height abi.ChainEpoch) (bool, error) { msg, ok := data.(*types.Message) if data != nil && !ok { panic("expected msg") } ml, err := me.cs.StateSearchMsg(ctx, ts.Key(), msg.Cid(), stmgr.LookbackNoLimit, true) if err != nil { return false, err } if ml == nil { return msgHnd(msg, nil, ts, height) } return msgHnd(msg, &ml.Receipt, ts, height) } id, err := me.hcAPI.onHeadChanged(ctx, check, hnd, rev, confidence, timeout) if err != nil { return err } me.lk.Lock() defer me.lk.Unlock() me.matchers[id] = mf return nil } // Convenience function for checking and matching messages func (me *messageEvents) CalledMsg(ctx context.Context, hnd MsgHandler, rev RevertHandler, confidence int, timeout abi.ChainEpoch, msg types.ChainMsg) error { return me.Called(ctx, me.CheckMsg(msg, hnd), hnd, rev, confidence, timeout, me.MatchMsg(msg.VMMessage())) }