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silverwindandbircni
ed940db4f0
A successful host step whose background child kept its output open failed with `exec: WaitDelay expired before I/O complete`. Like GitHub's runner (`ProcessExitedHandler` in https://github.com/actions/runner/blob/main/src/Runner.Sdk/ProcessInvoker.cs), the step now succeeds after the drain timeout. The leftover is killed only on Windows, as GitHub does there. A step whose timeout or cancellation hits during the drain still fails. Fixes: https://gitea.com/gitea/runner/issues/1290 Co-authored-by: bircni <[email protected]> Reviewed-on: https://gitea.com/gitea/runner/pulls/1323 Reviewed-by: bircni <[email protected]> Co-authored-by: silverwind <[email protected]>
82 lines
2.7 KiB
Go
82 lines
2.7 KiB
Go
// Copyright 2026 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package process
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import (
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"context"
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"errors"
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"os"
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"os/exec"
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"runtime"
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"sync/atomic"
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"time"
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)
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// treeKillWaitDelay bounds how long Wait lingers for the command's I/O pipes to
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// drain after the process exits before force-closing them and returning. It also
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// covers a command that backgrounds a process holding a pipe open after a clean
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// exit.
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const treeKillWaitDelay = 10 * time.Second
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// TreeKill wires an exec.Cmd so that cancelling it tears down the command's
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// whole process tree (see Killer) rather than only the direct child, and bounds
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// the post-exit I/O wait so a leftover pipe writer can never hang cmd.Wait.
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//
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// Background: a command often launches a process tree (a shell that starts a
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// child which spawns further background processes). The default
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// exec.CommandContext cancellation only kills the direct child, leaving the rest
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// of the tree running; and because the orphans inherit cmd's stdout/stderr pipe,
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// cmd.Wait() would block forever, hanging the caller.
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//
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// Callers still set cmd.SysProcAttr (via SysProcAttr) themselves, because the
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// value differs between the plain and PTY execution paths.
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type TreeKill struct {
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killer atomic.Pointer[Killer]
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}
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// NewTreeKill sets cmd.Cancel and cmd.WaitDelay. Call it before cmd.Start, then
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// call Capture once after a successful Start.
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func NewTreeKill(cmd *exec.Cmd) *TreeKill {
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t := &TreeKill{}
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cmd.Cancel = func() error {
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if k := t.killer.Load(); k != nil {
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return k.Kill()
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}
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if cmd.Process != nil {
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return cmd.Process.Kill()
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}
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return nil
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}
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cmd.WaitDelay = treeKillWaitDelay
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return t
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}
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// Capture assigns the started process (and the descendants it spawns) to a
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// Killer so cancellation can reach the whole tree — a Job Object on Windows
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// (children spawned afterwards are auto-included) and the process group on Unix.
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// Call it once after cmd.Start. On failure the command falls back to the default
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// single-process kill and the returned error is for logging only; WaitDelay
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// still bounds the wait. The returned Killer should be closed when the command
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// finishes (Close is nil-safe).
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func (t *TreeKill) Capture(p *os.Process) (*Killer, error) {
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k, err := NewKiller(p)
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if err != nil {
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return nil, err
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}
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t.killer.Store(k)
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return k, nil
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}
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// Wait is cmd.Wait, but like GitHub's runner a leftover holding a successful command's output does not fail it, and is killed only on Windows.
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func (t *TreeKill) Wait(ctx context.Context, cmd *exec.Cmd) error {
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err := cmd.Wait()
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if !errors.Is(err, exec.ErrWaitDelay) || ctx.Err() != nil {
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return err
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}
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if runtime.GOOS == "windows" {
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_ = t.killer.Load().Kill()
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}
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return nil
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}
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