feat: add support for cached wallets in cosmos

chains/cosmos/runner/runner.go

@@ -100,7 +100,20 @@ func NewRunner(ctx context.Context, spec loadtesttypes.LoadTestSpec) (*Runner, e
 	logger.Info("deriving wallet keys", zap.Int("num_wallets", spec.NumWallets))
 	keyStart := time.Now()
 	privKeys := make([]types.PrivKey, 0, spec.NumWallets)
-	if spec.NumWallets > 0 {
+	if spec.Cache.ReadWalletsFrom != "" {
+		logger.Info(
+			"Reading cached private keys",
+			zap.String("file", spec.Cache.ReadWalletsFrom),
+			zap.Int("num_wallets", spec.NumWallets),
+		)
+
+		cachedPKs, err := wallet.ReadCachedPrivateKeys(spec.Cache.ReadWalletsFrom, spec.NumWallets)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read cached private keys: %w", err)
+		}
+
+		privKeys = cachedPKs
+	} else if spec.NumWallets > 0 {
 		for i := range spec.NumWallets {
 			derivedPrivKey, err := hd.Secp256k1.Derive()(
 				spec.BaseMnemonic,
@@ -112,12 +125,13 @@ func NewRunner(ctx context.Context, spec loadtesttypes.LoadTestSpec) (*Runner, e
 			}
 			privKeys = append(privKeys, &secp256k1.PrivKey{Key: derivedPrivKey})
 		}
+
+		logger.Info(
+			"derived wallet keys",
+			zap.Int("num_keys", len(privKeys)),
+			zap.Duration("duration", time.Since(keyStart)),
+		)
 	}
-	logger.Info(
-		"derived wallet keys",
-		zap.Int("num_keys", len(privKeys)),
-		zap.Duration("duration", time.Since(keyStart)),
-	)
 
 	if len(privKeys) == 0 {
 		return nil, fmt.Errorf("no private keys available: either provide base mnemonic or private keys")

chains/cosmos/wallet/cache.go

@@ -0,0 +1,56 @@
+package wallet
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/cosmos/cosmos-sdk/crypto/types"
+	"github.com/cosmos/evm/crypto/ethsecp256k1"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// ReadCachedPrivateKeys reads the cached private keys from the file and returns them as types.PrivKey
+// The file is expected to be in the same format as the Ethereum keys cache.
+// See chains/ethereum/wallet/ReadWalletsFromCache() for more details.
+func ReadCachedPrivateKeys(filename string, num int) ([]types.PrivKey, error) {
+	bz, err := os.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("unable to open cache file %s: %w", filename, err)
+	}
+
+	type cachedKey struct {
+		Signer struct {
+			PK []byte
+		}
+	}
+
+	var cachedKeys []cachedKey
+	if err := json.Unmarshal(bz, &cachedKeys); err != nil {
+		return nil, fmt.Errorf("decoding cached wallets: %w", err)
+	}
+
+	if len(cachedKeys) < num {
+		return nil, fmt.Errorf("not enough cached keys (got %d, want %d)", len(cachedKeys), num)
+	}
+
+	if num > 0 && num < len(cachedKeys) {
+		cachedKeys = cachedKeys[:num]
+	}
+
+	privateKeys := make([]types.PrivKey, len(cachedKeys))
+	for i, key := range cachedKeys {
+		rawPK := key.Signer.PK
+
+		ecdsaPK, err := crypto.ToECDSA(rawPK)
+		if err != nil {
+			return nil, fmt.Errorf("parsing cached wallet %d private key: %w", i, err)
+		}
+
+		privateKeys[i] = &ethsecp256k1.PrivKey{
+			Key: crypto.FromECDSA(ecdsaPK),
+		}
+	}
+
+	return privateKeys, nil
+}