aggregate.go

// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package vterrors

import (
	"sort"
	"strings"

	vtrpcpb "github.com/youtube/vitess/go/vt/proto/vtrpc"
)

// A list of all vtrpcpb.Code, ordered by priority. These priorities are
// used when aggregating multiple errors in VtGate.
// Higher priority error codes are more urgent for users to see. They are
// prioritized based on the following question: assuming a scatter query produced multiple
// errors, which of the errors is the most likely to give the user useful information
// about why the query failed and how they should proceed?
const (
	// Informational errors.
	PriorityOK = iota
	PriorityCanceled
	PriorityAlreadyExists
	PriorityOutOfRange
	// Potentially retryable errors.
	PriorityUnavailable
	PriorityDeadlineExceeded
	PriorityAborted
	PriorityFailedPrecondition
	// Permanent errors.
	PriorityResourceExhausted
	PriorityUnknown
	PriorityUnauthenticated
	PriorityPermissionDenied
	PriorityInvalidArgument
	PriorityNotFound
	PriorityUnimplemented
	// Serious errors.
	PriorityInternal
	PriorityDataLoss
)

var errorPriorities = map[vtrpcpb.Code]int{
	vtrpcpb.Code_OK:                  PriorityOK,
	vtrpcpb.Code_CANCELED:            PriorityCanceled,
	vtrpcpb.Code_UNKNOWN:             PriorityUnknown,
	vtrpcpb.Code_INVALID_ARGUMENT:    PriorityInvalidArgument,
	vtrpcpb.Code_DEADLINE_EXCEEDED:   PriorityDeadlineExceeded,
	vtrpcpb.Code_NOT_FOUND:           PriorityNotFound,
	vtrpcpb.Code_ALREADY_EXISTS:      PriorityAlreadyExists,
	vtrpcpb.Code_PERMISSION_DENIED:   PriorityPermissionDenied,
	vtrpcpb.Code_UNAUTHENTICATED:     PriorityUnauthenticated,
	vtrpcpb.Code_RESOURCE_EXHAUSTED:  PriorityResourceExhausted,
	vtrpcpb.Code_FAILED_PRECONDITION: PriorityFailedPrecondition,
	vtrpcpb.Code_ABORTED:             PriorityAborted,
	vtrpcpb.Code_OUT_OF_RANGE:        PriorityOutOfRange,
	vtrpcpb.Code_UNIMPLEMENTED:       PriorityUnimplemented,
	vtrpcpb.Code_INTERNAL:            PriorityInternal,
	vtrpcpb.Code_UNAVAILABLE:         PriorityUnavailable,
	vtrpcpb.Code_DATA_LOSS:           PriorityDataLoss,
}

// Aggregate aggregates several errors into a single one.
// The resulting error code will be the one with the highest
// priority as defined by the priority constants in this package.
func Aggregate(errors []error) error {
	if len(errors) == 0 {
		return nil
	}
	return New(aggregateCodes(errors), aggregateErrors(errors))
}

func aggregateCodes(errors []error) vtrpcpb.Code {
	highCode := vtrpcpb.Code_OK
	for _, e := range errors {
		code := Code(e)
		if errorPriorities[code] > errorPriorities[highCode] {
			highCode = code
		}
	}
	return highCode
}

// ConcatenateErrors aggregates an array of errors into a single error by string concatenation.
func aggregateErrors(errs []error) string {
	errStrs := make([]string, 0, len(errs))
	for _, e := range errs {
		errStrs = append(errStrs, e.Error())
	}
	// sort the error strings so we always have deterministic ordering
	sort.Strings(errStrs)
	return strings.Join(errStrs, "\n")
}