store and load latest chain head in the datastore

chain/chain.go

@@ -24,6 +24,8 @@ const ForkLengthThreshold = 20
 
 var log = logging.Logger("f2")
 
+var chainHeadKey = dstore.NewKey("head")
+
 type GenesisBootstrap struct {
 	Genesis  *BlockHeader
 	MinerKey address.Address
@@ -232,6 +234,40 @@ func NewChainStore(bs bstore.Blockstore, ds dstore.Batching) *ChainStore {
 	}
 }
 
+func (cs *ChainStore) Load() error {
+	head, err := cs.ds.Get(chainHeadKey)
+	if err != nil {
+		return errors.Wrap(err, "failed to load chain state from datastore")
+	}
+
+	var tscids []cid.Cid
+	if err := json.Unmarshal(head, &tscids); err != nil {
+		return errors.Wrap(err, "failed to unmarshal stored chain head")
+	}
+
+	ts, err := cs.LoadTipSet(tscids)
+	if err != nil {
+		return err
+	}
+
+	cs.heaviest = ts
+
+	return nil
+}
+
+func (cs *ChainStore) writeHead(ts *TipSet) error {
+	data, err := json.Marshal(ts.Cids())
+	if err != nil {
+		return errors.Wrap(err, "failed to marshal tipset")
+	}
+
+	if err := cs.ds.Put(chainHeadKey, data); err != nil {
+		return errors.Wrap(err, "failed to write chain head to datastore")
+	}
+
+	return nil
+}
+
 func (cs *ChainStore) SubNewTips() chan *TipSet {
 	subch := cs.bestTips.Sub("best")
 	out := make(chan *TipSet)
@@ -315,6 +351,12 @@ func (cs *ChainStore) maybeTakeHeavierTipSet(ts *TipSet) error {
 		}
 		log.Infof("New heaviest tipset! %s", ts.Cids())
 		cs.heaviest = ts
+
+		if err := cs.writeHead(ts); err != nil {
+			// TODO: should this error? we've already accepted it as our best
+			// head and told everyone...
+			return err
+		}
 	}
 	return nil
 }

miner/miner.go

@@ -38,8 +38,9 @@ type api interface {
 
 func NewMiner(api api, addr address.Address) *Miner {
 	return &Miner{
-		api:   api,
+		api:     api,
-		Delay: time.Second * 4,
+		address: addr,
+		Delay:   time.Second * 4,
 	}
 }