contexts: make sure to abort when a context is canceled

Also, buffer single-use channels we may walk away from. This was showing
up (rarely) in a go-ipfs test.


This commit was moved from ipfs/go-bitswap@0cbfff7

bitswap/peermanager/peermanager.go

@@ -59,9 +59,18 @@ func New(ctx context.Context, createPeerQueue PeerQueueFactory) *PeerManager {
 
 // ConnectedPeers returns a list of peers this PeerManager is managing.
 func (pm *PeerManager) ConnectedPeers() []peer.ID {
-	resp := make(chan []peer.ID)
-	pm.peerMessages <- &getPeersMessage{resp}
-	return <-resp
+	resp := make(chan []peer.ID, 1)
+	select {
+	case pm.peerMessages <- &getPeersMessage{resp}:
+	case <-pm.ctx.Done():
+		return nil
+	}
+	select {
+	case peers := <-resp:
+		return peers
+	case <-pm.ctx.Done():
+		return nil
+	}
 }
 
 // Connected is called to add a new peer to the pool, and send it an initial set

bitswap/sessionpeermanager/sessionpeermanager.go

@@ -82,7 +82,7 @@ func (spm *SessionPeerManager) RecordPeerRequests(p []peer.ID, ks []cid.Cid) {
 func (spm *SessionPeerManager) GetOptimizedPeers() []peer.ID {
 	// right now this just returns all peers, but soon we might return peers
 	// ordered by optimization, or only a subset
-	resp := make(chan []peer.ID)
+	resp := make(chan []peer.ID, 1)
 	select {
 	case spm.peerMessages <- &peerReqMessage{resp}:
 	case <-spm.ctx.Done():
@@ -108,11 +108,16 @@ func (spm *SessionPeerManager) FindMorePeers(ctx context.Context, c cid.Cid) {
 		// - share peers between sessions based on interest set
 		for p := range spm.network.FindProvidersAsync(ctx, k, 10) {
 			go func(p peer.ID) {
+				// TODO: Also use context from spm.
 				err := spm.network.ConnectTo(ctx, p)
 				if err != nil {
 					log.Debugf("failed to connect to provider %s: %s", p, err)
 				}
-				spm.peerMessages <- &peerFoundMessage{p}
+				select {
+				case spm.peerMessages <- &peerFoundMessage{p}:
+				case <-ctx.Done():
+				case <-spm.ctx.Done():
+				}
 			}(p)
 		}
 	}(c)

bitswap/sessionrequestsplitter/sessionrequestsplitter.go

@@ -51,7 +51,7 @@ func New(ctx context.Context) *SessionRequestSplitter {
 // SplitRequest splits a request for the given cids one or more times among the
 // given peers.
 func (srs *SessionRequestSplitter) SplitRequest(peers []peer.ID, ks []cid.Cid) []*PartialRequest {
-	resp := make(chan []*PartialRequest)
+	resp := make(chan []*PartialRequest, 1)
 
 	select {
 	case srs.messages <- &splitRequestMessage{peers, ks, resp}:

bitswap/wantmanager/wantmanager.go

@@ -83,30 +83,66 @@ func (wm *WantManager) CancelWants(ctx context.Context, ks []cid.Cid, peers []pe
 
 // IsWanted returns whether a CID is currently wanted.
 func (wm *WantManager) IsWanted(c cid.Cid) bool {
-	resp := make(chan bool)
-	wm.wantMessages <- &isWantedMessage{c, resp}
-	return <-resp
+	resp := make(chan bool, 1)
+	select {
+	case wm.wantMessages <- &isWantedMessage{c, resp}:
+	case <-wm.ctx.Done():
+		return false
+	}
+	select {
+	case wanted := <-resp:
+		return wanted
+	case <-wm.ctx.Done():
+		return false
+	}
 }
 
 // CurrentWants returns the list of current wants.
 func (wm *WantManager) CurrentWants() []*wantlist.Entry {
-	resp := make(chan []*wantlist.Entry)
-	wm.wantMessages <- &currentWantsMessage{resp}
-	return <-resp
+	resp := make(chan []*wantlist.Entry, 1)
+	select {
+	case wm.wantMessages <- &currentWantsMessage{resp}:
+	case <-wm.ctx.Done():
+		return nil
+	}
+	select {
+	case wantlist := <-resp:
+		return wantlist
+	case <-wm.ctx.Done():
+		return nil
+	}
 }
 
 // CurrentBroadcastWants returns the current list of wants that are broadcasts.
 func (wm *WantManager) CurrentBroadcastWants() []*wantlist.Entry {
-	resp := make(chan []*wantlist.Entry)
-	wm.wantMessages <- &currentBroadcastWantsMessage{resp}
-	return <-resp
+	resp := make(chan []*wantlist.Entry, 1)
+	select {
+	case wm.wantMessages <- &currentBroadcastWantsMessage{resp}:
+	case <-wm.ctx.Done():
+		return nil
+	}
+	select {
+	case wl := <-resp:
+		return wl
+	case <-wm.ctx.Done():
+		return nil
+	}
 }
 
 // WantCount returns the total count of wants.
 func (wm *WantManager) WantCount() int {
-	resp := make(chan int)
-	wm.wantMessages <- &wantCountMessage{resp}
-	return <-resp
+	resp := make(chan int, 1)
+	select {
+	case wm.wantMessages <- &wantCountMessage{resp}:
+	case <-wm.ctx.Done():
+		return 0
+	}
+	select {
+	case count := <-resp:
+		return count
+	case <-wm.ctx.Done():
+		return 0
+	}
 }
 
 // Startup starts processing for the WantManager.

bitswap/workers.go

@@ -217,11 +217,15 @@ func (bs *Bitswap) rebroadcastWorker(parent context.Context) {
 			// TODO: come up with a better strategy for determining when to search
 			// for new providers for blocks.
 			i := rand.Intn(len(entries))
-			bs.findKeys <- &blockRequest{
+			select {
+			case bs.findKeys <- &blockRequest{
 				Cid: entries[i].Cid,
 				Ctx: ctx,
+			}:
+			case <-ctx.Done():
+				return
 			}
-		case <-parent.Done():
+		case <-ctx.Done():
 			return
 		}
 	}