feat(GODT-2802): Ordered task cancellation
Add `OrderedCancelGroup` type to enforce the cancellation of go routines in a reverse order. Additionally this type waits for the go-routine to finish before proceeding to the next one. We need this to guarantee that all the user services shut down properly without deadlocking.
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// Copyright (c) 2023 Proton AG
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//
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// This file is part of Proton Mail Bridge.
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//
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// Proton Mail Bridge 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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// Proton Mail Bridge 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 Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
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package orderedtasks
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import (
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"context"
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"github.com/ProtonMail/gluon/async"
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gl "github.com/ProtonMail/gluon/logging"
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"github.com/bradenaw/juniper/xslices"
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"golang.org/x/exp/slices"
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)
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type task struct {
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done func()
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ch chan struct{}
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}
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func (t *task) cancelAndWait() {
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t.cancel()
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t.wait()
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}
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func (t *task) cancel() {
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t.done()
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}
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func (t *task) wait() {
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<-t.ch
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}
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// OrderedCancelGroup cancels go routines in reverse order that they are launched and waits for completion before
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// advancing to the next one.
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type OrderedCancelGroup struct {
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cancels []*task
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panicHandler async.PanicHandler
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}
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func NewOrderedCancelGroup(handler async.PanicHandler) *OrderedCancelGroup {
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return &OrderedCancelGroup{panicHandler: handler}
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}
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func (o *OrderedCancelGroup) Go(ctx context.Context, userID, debugName string, f func(ctx context.Context)) {
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ctx, cancel := context.WithCancel(ctx)
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task := &task{done: cancel, ch: make(chan struct{})}
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go func() {
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gl.DoAnnotated(ctx, func(ctx context.Context) {
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defer async.HandlePanic(o.panicHandler)
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defer close(task.ch)
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f(ctx)
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}, gl.Labels{"group": debugName, "user": userID})
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}()
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o.cancels = append(o.cancels, task)
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}
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func (o *OrderedCancelGroup) reversed() []*task {
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s := slices.Clone(o.cancels)
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xslices.Reverse(s)
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return s
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}
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func (o *OrderedCancelGroup) CancelAndWait() {
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for _, t := range o.reversed() {
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t.cancelAndWait()
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}
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o.cancels = nil
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}
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func (o *OrderedCancelGroup) Cancel() {
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for _, t := range o.reversed() {
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t.cancel()
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}
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}
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func (o *OrderedCancelGroup) Wait() {
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for _, t := range o.reversed() {
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t.wait()
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}
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o.cancels = nil
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}
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