eth/fetcher: lower max cache size, add timeout slack

eth/fetcher/fetcher.go

@@ -3,6 +3,7 @@ package fetcher
 
 import (
 	"errors"
+	"fmt"
 	"math/rand"
 	"time"
 
@@ -15,9 +16,10 @@ import (
 
 const (
 	arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested
+	gatherSlack   = 100 * time.Millisecond // Interval used to collate almost-expired announces with fetches
 	fetchTimeout  = 5 * time.Second        // Maximum alloted time to return an explicitly requested block
 	maxUncleDist  = 7                      // Maximum allowed backward distance from the chain head
-	maxQueueDist  = 256                    // Maximum allowed distance from the chain head to queue
+	maxQueueDist  = 32                     // Maximum allowed distance from the chain head to queue
 )
 
 var (
@@ -239,7 +241,7 @@ func (f *Fetcher) loop() {
 			request := make(map[string][]common.Hash)
 
 			for hash, announces := range f.announced {
-				if time.Since(announces[0].time) > arriveTimeout {
+				if time.Since(announces[0].time) > arriveTimeout-gatherSlack {
 					announce := announces[rand.Intn(len(announces))]
 					if f.getBlock(hash) == nil {
 						request[announce.origin] = append(request[announce.origin], hash)
@@ -249,7 +251,16 @@ func (f *Fetcher) loop() {
 				}
 			}
 			// Send out all block requests
-			for _, hashes := range request {
+			for peer, hashes := range request {
+				if glog.V(logger.Detail) && len(hashes) > 0 {
+					list := "["
+					for _, hash := range hashes {
+						list += fmt.Sprintf("%x, ", hash[:4])
+					}
+					list = list[:len(list)-2] + "]"
+
+					glog.V(logger.Detail).Infof("Peer %s: fetching %s", peer, list)
+				}
 				go f.fetching[hashes[0]].fetch(hashes)
 			}
 			// Schedule the next fetch if blocks are still pending
@@ -319,7 +330,7 @@ func (f *Fetcher) enqueue(peer string, block *types.Block) {
 
 	// Discard any past or too distant blocks
 	if dist := int64(block.NumberU64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist {
-		glog.V(logger.Detail).Infof("Peer %s: discarded block #%d [%x], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist)
+		glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist)
 		return
 	}
 	// Schedule the block for future importing