mitigate unexpected state

signer/cosigner_nonce_cache.go

@@ -375,21 +375,29 @@ func (cnc *CosignerNonceCache) PruneNonces() int {
 	cnc.cache.mu.Lock()
 	defer cnc.cache.mu.Unlock()
 	nonExpiredIndex := len(cnc.cache.cache) - 1
-	for i := len(cnc.cache.cache) - 1; i >= 0; i-- {
+	total := len(cnc.cache.cache)
+	for i := total - 1; i >= 0; i-- {
 		if time.Now().Before(cnc.cache.cache[i].Expiration) {
 			nonExpiredIndex = i
 			break
 		}
 		if i == 0 {
 			deleteCount := len(cnc.cache.cache)
 			cnc.cache.cache = nil
+			cnc.logger.Debug("Pruned all nonces due to expiration", "deleted", deleteCount, "total", total)
 			return deleteCount
 		}
 	}
-	deleteCount := len(cnc.cache.cache) - nonExpiredIndex - 1
-	if nonExpiredIndex != len(cnc.cache.cache)-1 {
+	deleteCount := total - nonExpiredIndex - 1
+	if nonExpiredIndex != total-1 {
 		cnc.cache.cache = cnc.cache.cache[:nonExpiredIndex+1]
 	}
+	if deleteCount > 0 {
+		cnc.logger.Debug("Pruned some nonces due to expiration", "deleted", deleteCount, "total", total)
+	} else {
+		cnc.logger.Debug("No nonces pruned due to expiration", "total", total)
+	}
+
 	return deleteCount
 }
 
@@ -418,3 +426,9 @@ func (cnc *CosignerNonceCache) ClearNonces(cosigner Cosigner) {
 		}
 	}
 }
+
+func (cnc *CosignerNonceCache) ClearAllNonces() {
+	cnc.cache.mu.Lock()
+	defer cnc.cache.mu.Unlock()
+	cnc.cache.cache = nil
+}

signer/cosigner_nonce_cache_test.go

@@ -98,7 +98,23 @@ func TestClearNonces(t *testing.T) {
 
 	for _, n := range cnc.cache.cache {
 		require.Len(t, n.Nonces, 2)
+		oneFound := false
+		twoFound := false
+		for _, cnr := range n.Nonces {
+			if cnr.Cosigner == cosigners[1] {
+				oneFound = true
+			}
+			if cnr.Cosigner == cosigners[2] {
+				twoFound = true
+			}
+		}
+		require.True(t, oneFound)
+		require.True(t, twoFound)
 	}
+
+	cnc.ClearNonces(cosigners[1])
+
+	require.Equal(t, 0, cnc.cache.Size())
 }
 
 type mockPruner struct {

signer/threshold_validator.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -734,7 +735,13 @@ func (pv *ThresholdValidator) Sign(ctx context.Context, chainID string, block Bl
 						"err", err.Error(),
 					)
 
-					if cosigner.GetID() == pv.myCosigner.GetID() {
+					isMyCosigner := cosigner.GetID() == pv.myCosigner.GetID()
+
+					if strings.Contains(err.Error(), "unexpected state, metadata does not exist for U:") {
+						pv.nonceCache.ClearNonces(cosigner)
+					}
+
+					if isMyCosigner {
 						return err
 					}