fix: Add reaper to coder agent #2441
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| // Package reaper contains logic for reaping subprocesses. It is | ||
| // specifically used in the agent to avoid the accumulation of | ||
| // zombie processes. | ||
| package reaper |
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| Original file line number | Diff line number | Diff line change |
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| //go:build !linux | ||
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| package reaper | ||
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| import "github.com/hashicorp/go-reap" | ||
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| // IsChild returns true if we're the forked process. | ||
| func IsChild() bool { | ||
| return false | ||
| } | ||
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| // IsInitProcess returns true if the current process's PID is 1. | ||
| func IsInitProcess() bool { | ||
| return false | ||
| } | ||
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| func ForkReap(pids reap.PidCh) error { | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,66 @@ | ||
| //go:build linux | ||
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| package reaper_test | ||
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| import ( | ||
| "os" | ||
| "os/exec" | ||
| "testing" | ||
| "time" | ||
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| "github.com/hashicorp/go-reap" | ||
| "github.com/stretchr/testify/require" | ||
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| "github.com/coder/coder/agent/reaper" | ||
| ) | ||
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| func TestReap(t *testing.T) { | ||
| t.Parallel() | ||
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| // Don't run the reaper test in CI. It does weird | ||
| // things like forkexecing which may have unintended | ||
| // consequences in CI. | ||
| if _, ok := os.LookupEnv("CI"); ok { | ||
| t.Skip("Detected CI, skipping reaper tests") | ||
| } | ||
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| // Because we're forkexecing these tests will try to run twice... | ||
| if reaper.IsChild() { | ||
| t.Skip("I'm a child!") | ||
| } | ||
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| // OK checks that's the reaper is successfully reaping | ||
| // exited processes and passing the PIDs through the shared | ||
| // channel. | ||
| t.Run("OK", func(t *testing.T) { | ||
| pids := make(reap.PidCh, 1) | ||
| err := reaper.ForkReap(pids) | ||
| require.NoError(t, err) | ||
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| cmd := exec.Command("tail", "-f", "/dev/null") | ||
| err = cmd.Start() | ||
| require.NoError(t, err) | ||
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| cmd2 := exec.Command("tail", "-f", "/dev/null") | ||
| err = cmd2.Start() | ||
| require.NoError(t, err) | ||
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| err = cmd.Process.Kill() | ||
| require.NoError(t, err) | ||
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| err = cmd2.Process.Kill() | ||
| require.NoError(t, err) | ||
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| expectedPIDs := []int{cmd.Process.Pid, cmd2.Process.Pid} | ||
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| deadline := time.NewTimer(time.Second * 5) | ||
| for i := 0; i < len(expectedPIDs); i++ { | ||
| select { | ||
| case <-deadline.C: | ||
| t.Fatalf("Timed out waiting for process") | ||
| case pid := <-pids: | ||
| require.Contains(t, expectedPIDs, pid) | ||
| } | ||
| } | ||
| }) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| //go:build linux | ||
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| package reaper | ||
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| import ( | ||
| "fmt" | ||
| "os" | ||
| "syscall" | ||
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| "github.com/hashicorp/go-reap" | ||
| "golang.org/x/xerrors" | ||
| ) | ||
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| // agentEnvMark is a simple environment variable that we use as a marker | ||
| // to indicated that the process is a child as opposed to the reaper. | ||
| // Since we are forkexec'ing we need to be able to differentiate between | ||
| // the two to avoid fork bombing ourselves. | ||
| const agentEnvMark = "CODER_DO_NOT_REAP" | ||
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| // IsChild returns true if we're the forked process. | ||
| func IsChild() bool { | ||
| return os.Getenv(agentEnvMark) != "" | ||
| } | ||
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| // IsInitProcess returns true if the current process's PID is 1. | ||
| func IsInitProcess() bool { | ||
| return os.Getpid() == 1 | ||
| } | ||
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| // ForkReap spawns a goroutine that reaps children. In order to avoid | ||
| // complications with spawning `exec.Commands` in the same process that | ||
| // is reaping, we forkexec a child process. This prevents a race between | ||
| // the reaper and an exec.Command waiting for its process to complete. | ||
| // The provided 'pids' channel may be nil if the caller does not care about the | ||
| // reaped children PIDs. | ||
| func ForkReap(pids reap.PidCh) error { | ||
| // Check if the process is the parent or the child. | ||
| // If it's the child we want to skip attempting to reap. | ||
| if IsChild() { | ||
| return nil | ||
| } | ||
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| go reap.ReapChildren(pids, nil, nil, nil) | ||
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| args := os.Args | ||
| // This is simply done to help identify the real agent process | ||
| // when viewing in something like 'ps'. | ||
| args = append(args, "#Agent") | ||
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| pwd, err := os.Getwd() | ||
| if err != nil { | ||
| return xerrors.Errorf("get wd: %w", err) | ||
| } | ||
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| pattrs := &syscall.ProcAttr{ | ||
| Dir: pwd, | ||
| // Add our marker for identifying the child process. | ||
| Env: append(os.Environ(), fmt.Sprintf("%s=true", agentEnvMark)), | ||
|
There was a problem hiding this comment. Should we filter this out from sub-process envs (i.e. when we launch shells)? It probably doesn't matter for correctness, more of a cleanliness thing. We could also add There was a problem hiding this comment. I agree that it's certainly cleaner to filter it out. The only reason I didn't is because I did not want implementation details of the I think if it becomes an issue we devote some time to figuring out something unobtrusive. There was a problem hiding this comment. I already merged this but I think a cleaner solution is to have a There was a problem hiding this comment. That makes sense and I agree that's a clean solution @sreya. 👍🏻 |
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| Sys: &syscall.SysProcAttr{ | ||
| Setsid: true, | ||
| }, | ||
| Files: []uintptr{ | ||
| uintptr(syscall.Stdin), | ||
| uintptr(syscall.Stdout), | ||
| uintptr(syscall.Stderr), | ||
| }, | ||
| } | ||
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| //#nosec G204 | ||
| pid, _ := syscall.ForkExec(args[0], args, pattrs) | ||
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| var wstatus syscall.WaitStatus | ||
| _, err = syscall.Wait4(pid, &wstatus, 0, nil) | ||
| for xerrors.Is(err, syscall.EINTR) { | ||
| _, err = syscall.Wait4(pid, &wstatus, 0, nil) | ||
| } | ||
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| return nil | ||
| } | ||
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