fix random error

Author: sheldon

modules/random/keeper/service.go

@@ -2,8 +2,6 @@ package keeper
 
 import (
 	"encoding/hex"
-	"math/rand"
-	"time"
 
 	"github.com/tidwall/gjson"
 
@@ -37,9 +35,15 @@ func (k Keeper) RequestService(ctx sdk.Context, consumer sdk.AccAddress, service
 	if coins := k.bankKeeper.SpendableCoins(ctx, consumer); !coins.IsAllGTE(serviceFeeCap) {
 		return nil, sdkerrors.ErrInsufficientFee
 	}
+	prng := types.MakePRNG(
+		ctx.BlockHeader().LastBlockId.Hash,
+		ctx.BlockHeader().Time.UnixNano(),
+		consumer, nil, true)
+	provider, err := sdk.AccAddressFromBech32(bindings[prng.Intn(len(bindings))].Provider)
+	if err != nil {
+		return nil, err
+	}
 
-	rand.Seed(time.Now().UnixNano())
-	provider, _ := sdk.AccAddressFromBech32(bindings[rand.Intn(len(bindings))].Provider)
 	timeout := k.serviceKeeper.GetParams(ctx).MaxRequestTimeout
 
 	return k.serviceKeeper.CreateRequestContext(

modules/random/types/rng.go

@@ -3,6 +3,7 @@ package types
 import (
 	"crypto/sha256"
 	"math/big"
+	"math/rand"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
@@ -59,6 +60,11 @@ func (p PRNG) GetRand() *big.Rat {
 	return random
 }
 
+func (p PRNG) Intn(n int) int {
+	rnd := rand.New(rand.NewSource(p.GetRand().Denom().Int64()))
+	return rnd.Intn(n)
+}
+
 // SHA256 wraps sha256.Sum256 with result converted to slice
 func SHA256(data []byte) []byte {
 	sum := sha256.Sum256(data)