Add error buffer util

core/utils/utils.go

@@ -17,14 +17,16 @@ import (
 	"sync/atomic"
 	"time"
 
+	"errors"
+
 	cryptop2p "github.com/libp2p/go-libp2p-core/crypto"
 	"golang.org/x/exp/constraints"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/jpillora/backoff"
 	"github.com/libp2p/go-libp2p-core/peer"
-	"github.com/pkg/errors"
+	pkgerrors "github.com/pkg/errors"
 	"github.com/robfig/cron/v3"
 	uuid "github.com/satori/go.uuid"
 	"golang.org/x/crypto/bcrypt"
@@ -118,7 +120,7 @@ func NewSecret(n int) string {
 	b := make([]byte, n)
 	_, err := rand.Read(b)
 	if err != nil {
-		panic(errors.Wrap(err, "generating secret failed"))
+		panic(pkgerrors.Wrap(err, "generating secret failed"))
 	}
 	return base64.StdEncoding.EncodeToString(b)
 }
@@ -296,7 +298,7 @@ func Sha256(in string) (string, error) {
 	hasher := sha3.New256()
 	_, err := hasher.Write([]byte(in))
 	if err != nil {
-		return "", errors.Wrap(err, "sha256 write error")
+		return "", pkgerrors.Wrap(err, "sha256 write error")
 	}
 	return hex.EncodeToString(hasher.Sum(nil)), nil
 }
@@ -374,7 +376,7 @@ func CheckUint256(n *big.Int) error {
 func HexToUint256(s string) (*big.Int, error) {
 	rawNum, err := hexutil.Decode(s)
 	if err != nil {
-		return nil, errors.Wrapf(err, "while parsing %s as hex: ", s)
+		return nil, pkgerrors.Wrapf(err, "while parsing %s as hex: ", s)
 	}
 	rv := big.NewInt(0).SetBytes(rawNum) // can't be negative number
 	if err := CheckUint256(rv); err != nil {
@@ -625,7 +627,7 @@ func (q *BoundedPriorityQueue[T]) Empty() bool {
 //	}
 func WrapIfError(err *error, msg string) {
 	if *err != nil {
-		*err = errors.Wrap(*err, msg)
+		*err = pkgerrors.Wrap(*err, msg)
 	}
 }
 
@@ -744,7 +746,7 @@ func ValidateCronSchedule(schedule string) error {
 	}
 	parser := cron.NewParser(cron.SecondOptional | cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor)
 	_, err := parser.Parse(schedule)
-	return errors.Wrapf(err, "invalid cron schedule '%v'", schedule)
+	return pkgerrors.Wrapf(err, "invalid cron schedule '%v'", schedule)
 }
 
 // ResettableTimer stores a timer
@@ -862,7 +864,7 @@ func (once *StartStopOnce) StartOnce(name string, fn func() error) error {
 	success := once.state.CompareAndSwap(int32(StartStopOnce_Unstarted), int32(StartStopOnce_Starting))
 
 	if !success {
-		return errors.Errorf("%v has already been started once; state=%v", name, StartStopOnceState(once.state.Load()))
+		return pkgerrors.Errorf("%v has already been started once; state=%v", name, StartStopOnceState(once.state.Load()))
 	}
 
 	once.Lock()
@@ -899,11 +901,11 @@ func (once *StartStopOnce) StopOnce(name string, fn func() error) error {
 		state := once.state.Load()
 		switch state {
 		case int32(StartStopOnce_Stopped):
-			return errors.Wrapf(ErrAlreadyStopped, "%s has already been stopped", name)
+			return pkgerrors.Wrapf(ErrAlreadyStopped, "%s has already been stopped", name)
 		case int32(StartStopOnce_Unstarted):
-			return errors.Wrapf(ErrCannotStopUnstarted, "%s has not been started", name)
+			return pkgerrors.Wrapf(ErrCannotStopUnstarted, "%s has not been started", name)
 		default:
-			return errors.Errorf("%v cannot be stopped from this state; state=%v", name, StartStopOnceState(state))
+			return pkgerrors.Errorf("%v cannot be stopped from this state; state=%v", name, StartStopOnceState(state))
 		}
 	}
 
@@ -1112,3 +1114,46 @@ func MinKey[U any, T constraints.Ordered](elems []U, key func(U) T) T {
 
 	return min
 }
+
+// ErrorBuffer uses joinedErrors interface to join multiple errors into a single error.
+// This is useful to track the most recent N errors in a service and flush them as a single error.
+
+type ErrorBuffer struct {
+	// buffer is a slice of errors
+	buffer []error
+	// Cap is the maximum number of errors that the buffer can hold.
+	// Exceeding the cap results in discarding the oldest error
+	Cap int
+
+	sync.RWMutex
+}
+
+func (eb *ErrorBuffer) Flush() (err error) {
+	eb.RLock()
+	defer eb.RUnlock()
+	err = errors.Join(eb.buffer...)
+	eb.buffer = nil
+	return
+}
+
+func (eb *ErrorBuffer) Append(incoming error) {
+	eb.Lock()
+	defer eb.Unlock()
+	// if at capacity, drop first element
+	if len(eb.buffer) == eb.Cap && eb.Cap != 0 {
+		eb.buffer = append(eb.buffer[1:], incoming)
+		return
+	}
+	eb.buffer = append(eb.buffer, incoming)
+}
+
+// UnwrapError returns a list of underlying errors if passed error implements joinedError or return the err in a single-element list otherwise.
+//
+//nolint:errorlint // error type checks will fail on wrapped errors. Disabled since we are not doing checks on error types.
+func UnwrapError(err error) []error {
+	joined, ok := err.(interface{ Unwrap() []error })
+	if !ok {
+		return []error{err}
+	}
+	return joined.Unwrap()
+}

core/utils/utils_test.go

@@ -983,3 +983,57 @@ func TestTryParseHex(t *testing.T) {
 		assert.Equal(t, []byte{0x1, 0x23}, b)
 	})
 }
+
+func TestErrorBuffer(t *testing.T) {
+	t.Parallel()
+
+	err1 := errors.New("err1")
+	err2 := errors.New("err2")
+	err3 := errors.New("err3")
+
+	t.Run("happy path", func(t *testing.T) {
+		t.Parallel()
+		buff := utils.ErrorBuffer{}
+		buff.Append(err1)
+		buff.Append(err2)
+		combined := buff.Flush()
+		errs := utils.UnwrapError(combined)
+		assert.Equal(t, 2, len(errs))
+		assert.Equal(t, err1.Error(), errs[0].Error())
+		assert.Equal(t, err2.Error(), errs[1].Error())
+	})
+
+	t.Run("ovewrite oldest error when cap exceeded", func(t *testing.T) {
+		t.Parallel()
+		buff := utils.ErrorBuffer{Cap: 2}
+		buff.Append(err1)
+		buff.Append(err2)
+		buff.Append(err3)
+		combined := buff.Flush()
+		errs := utils.UnwrapError(combined)
+		assert.Equal(t, 2, len(errs))
+		assert.Equal(t, err2.Error(), errs[0].Error())
+		assert.Equal(t, err3.Error(), errs[1].Error())
+	})
+
+	t.Run("does not overwrite the buffer if cap == 0", func(t *testing.T) {
+		t.Parallel()
+		buff := utils.ErrorBuffer{}
+		for i := 1; i <= 20; i++ {
+			buff.Append(errors.Errorf("err#%d", i))
+		}
+
+		combined := buff.Flush()
+		errs := utils.UnwrapError(combined)
+		assert.Equal(t, 20, len(errs))
+		assert.Equal(t, "err#20", errs[19].Error())
+	})
+
+	t.Run("UnwrapError returns the a single element err array if passed err is not a joinedError", func(t *testing.T) {
+		t.Parallel()
+		errs := utils.UnwrapError(err1)
+		assert.Equal(t, 1, len(errs))
+		assert.Equal(t, err1.Error(), errs[0].Error())
+	})
+
+}