Generated leaves start at the size of the tree

Without this change the generated leaves always start at size 0, which
means many writes are squashable as duplicates on the second run of the
tool. With this change, generated leaves will be unique except where the
intended duplicate generation code kicks in.

hammer/clients.go

@@ -85,7 +85,7 @@ func (r *LeafReader) Run(ctx context.Context) {
 		klog.V(2).Infof("LeafReader getting %d", i)
 		_, err := r.getLeaf(ctx, i, size)
 		if err != nil {
-			r.errchan <- fmt.Errorf("failed to get leaf: %v", err)
+			r.errchan <- fmt.Errorf("failed to get leaf %d: %v", i, err)
 		}
 	}
 }

hammer/hammer.go

@@ -59,6 +59,7 @@ var (
 			MaxIdleConnsPerHost: 256,
 			DisableKeepAlives:   false,
 		},
+		Timeout: 5 * time.Second,
 	}
 )
 
@@ -129,7 +130,7 @@ func NewHammer(tracker *client.LogStateTracker, f client.Fetcher, addURL *url.UR
 	for i := 0; i < *numReadersFull; i++ {
 		fullReaders[i] = NewLeafReader(tracker, f, MonotonicallyIncreasingNextLeaf(), *leafBundleSize, readThrottle.tokenChan, errChan)
 	}
-	gen := newLeafGenerator()
+	gen := newLeafGenerator(tracker.LatestConsistent.Size)
 	for i := 0; i < *numWriters; i++ {
 		writers[i] = NewLogWriter(hc, addURL, gen, writeThrottle.tokenChan, errChan)
 	}
@@ -207,11 +208,11 @@ func (h *Hammer) Run(ctx context.Context) {
 	}()
 }
 
-func newLeafGenerator() func() []byte {
+func newLeafGenerator(start uint64) func() []byte {
 	const dupChance = 0.1
-	var g int64
+	var g uint64 = start
 	return func() []byte {
-		var r int64
+		var r uint64
 		if rand.Float64() <= dupChance {
 			// This one will actually be unique, but the next iteration will
 			// duplicate it. In future, this duplication could be randomly