bdf5209f68
It's common in many concurrent engines to have a situation where we collect errors on shutdown. Errors can either because a context closed, or because some engine error happened. The latter, can also cause the former, leading to a list of returned errors. In these scenarios, we want to filter out all the secondary context errors, unless that's all that's there. This provides a helper function to do so.
121 lines
3.7 KiB
Go
121 lines
3.7 KiB
Go
// Mgmt
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// Copyright (C) James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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// Package errwrap contains some error helpers.
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package errwrap
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import (
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"context"
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"github.com/hashicorp/go-multierror"
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"github.com/pkg/errors"
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)
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// Wrapf adds a new error onto an existing chain of errors. If the new error to
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// be added is nil, then the old error is returned unchanged.
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func Wrapf(err error, format string, args ...interface{}) error {
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return errors.Wrapf(err, format, args...)
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}
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// Append can be used to safely append an error onto an existing one. If you
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// pass in a nil error to append, the existing error will be returned unchanged.
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// If the existing error is already nil, then the new error will be returned
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// unchanged. This makes it easy to use Append as a safe `reterr += err`, when
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// you don't know if either is nil or not.
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func Append(reterr, err error) error {
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if reterr == nil { // keep it simple, pass it through
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return err // which might even be nil
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}
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if err == nil { // no error, so don't do anything
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return reterr
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}
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// both are real errors
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return multierror.Append(reterr, err)
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}
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// Join takes a list of errors and combines them into a multierror with Append.
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func Join(errs []error) error {
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if len(errs) == 0 {
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return nil
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}
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if len(errs) == 1 {
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return errs[0]
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}
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var reterr error
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for _, e := range errs {
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reterr = Append(reterr, e)
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}
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return reterr
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}
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// WithoutContext passes through an error if it's nil or is a normal error. If
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// it is a multierror, then it removes all errors of context cancellation unless
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// that's all there is. If there's one error remaining, it returns that.
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// Otherwise it returns a new multierror with what's left.
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func WithoutContext(err error) error {
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if err == nil {
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return nil
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}
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multiErr, ok := err.(*multierror.Error)
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if !ok {
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return err
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}
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if len(multiErr.Errors) == 0 {
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return err // unexpected
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}
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errs := []error{}
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for _, e := range multiErr.Errors {
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if e == context.Canceled {
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continue // remove
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}
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errs = append(errs, e)
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}
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if len(errs) == 0 {
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return context.Canceled
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}
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//if len(errs) == 1 {
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// return errs[0]
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//}
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return Join(errs)
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}
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// String returns a string representation of the error. In particular, if the
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// error is nil, it returns an empty string instead of panicking.
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func String(err error) string {
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if err == nil {
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return ""
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}
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return err.Error()
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}
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