rapide: remove random source bookkeeping and use mrand.Int

This fallsback to fastrand in go1.21 and is well fast enough.

rapide/rapide.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	mrand "math/rand"
 	"sync"
 	"sync/atomic"
 
@@ -51,9 +50,8 @@ func (c *Client) Get(ctx context.Context, root cid.Cid, traversal ipsl.Traversal
 		errors: make([]error, len(c.ServerDrivenDownloaders)),
 	}
 
-	seedRand := mrand.New(mrand.NewSource(mrand.Int63()))
 	for i, sdd := range c.ServerDrivenDownloaders {
-		d.startServerDrivenWorker(ctx, sdd, &d.root, &d.errors[i], seedRand.Int63()^int64(i))
+		d.startServerDrivenWorker(ctx, sdd, &d.root, &d.errors[i])
 	}
 
 	return out

rapide/serverdriven.go

@@ -18,19 +18,17 @@ type serverDrivenWorker struct {
 	outErr   *error
 	current  *node
 	tasks    map[cid.Cid]*node
-	rand     mrand.Rand
 
 	// TODO: add a dontGoThere map which tells you what part of the dag this node is not able to handle
 }
 
-func (d *download) startServerDrivenWorker(ctx context.Context, impl ServerDrivenDownloader, root *node, outErr *error, seed int64) {
+func (d *download) startServerDrivenWorker(ctx context.Context, impl ServerDrivenDownloader, root *node, outErr *error) {
 	w := &serverDrivenWorker{
 		impl:     impl,
 		download: d,
 		outErr:   outErr,
 		current:  root,
 		tasks:    make(map[cid.Cid]*node),
-		rand:     *mrand.New(mrand.NewSource(seed)),
 	}
 
 	go w.work(ctx)
@@ -224,9 +222,9 @@ func (w *serverDrivenWorker) compareChildWithMinimums(child *node, minWorkers ui
 		// if scores are identical randomly select other nodes to randomly distribute where downloads are placed
 		if luck == 0 {
 			// lazy initialisation of luck, this allows to creating a random value when better values exists back to back
-			luck = uint(w.rand.Int())
+			luck = uint(mrand.Int())
 		}
-		newLuck := uint(w.rand.Int())
+		newLuck := uint(mrand.Int())
 		if newLuck >= luck {
 			break
 		}