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https://github.com/gravitational/teleport.git
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91 lines
2.9 KiB
Go
91 lines
2.9 KiB
Go
// Teleport
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// Copyright (C) 2024 Gravitational, Inc.
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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 Affero 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 Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package vnet
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import (
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"context"
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"errors"
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"fmt"
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"sync"
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"github.com/gravitational/trace"
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"golang.org/x/sync/errgroup"
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)
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func newProcessManager() (*ProcessManager, context.Context) {
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ctx, cancel := context.WithCancel(context.Background())
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g, ctx := errgroup.WithContext(ctx)
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pm := &ProcessManager{
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g: g,
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cancel: cancel,
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closed: make(chan struct{}),
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}
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pm.closeOnce = sync.OnceFunc(func() {
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close(pm.closed)
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})
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return pm, ctx
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}
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// ProcessManager handles background tasks needed to run VNet.
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// Its semantics are similar to an error group with a context, but it cancels the context whenever
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// any task returns prematurely, that is, a task exits while the context was not canceled.
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type ProcessManager struct {
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g *errgroup.Group
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cancel context.CancelFunc
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closed chan struct{}
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closeOnce func()
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}
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// AddCriticalBackgroundTask adds a function to the error group. [task] is expected to block until
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// the context returned by [newProcessManager] gets canceled. The context gets canceled either by
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// calling Close on [ProcessManager] or if any task returns.
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func (pm *ProcessManager) AddCriticalBackgroundTask(name string, task func() error) {
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pm.g.Go(func() error {
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err := task()
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if err == nil {
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// Make sure to always return an error so that the errgroup context is canceled.
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err = fmt.Errorf("critical task %q exited prematurely", name)
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}
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return trace.Wrap(err)
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})
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}
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// Wait blocks and waits for the background tasks to finish, which typically happens when another
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// goroutine calls Close on the process manager.
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func (pm *ProcessManager) Wait() error {
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err := pm.g.Wait()
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select {
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case <-pm.closed:
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// Errors are expected after the process manager has been closed,
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// usually due to context cancellation, but other error types may be
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// returned. Log unexpected errors at debug level but return nil.
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if err != nil && !errors.Is(err, context.Canceled) {
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log.DebugContext(context.Background(), "ProcessManager exited with error after being closed", "error", err)
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}
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return nil
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default:
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return trace.Wrap(err)
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}
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}
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// Close stops any active background tasks by canceling the underlying context,
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// and waits for all tasks to terminate.
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func (pm *ProcessManager) Close() {
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pm.closeOnce()
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pm.cancel()
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}
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