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fix: use raw syscalls to write binary we execute #11684

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Merged
merged 1 commit into from
Jan 18, 2024
Merged

fix: use raw syscalls to write binary we execute #11684

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8 changes: 8 additions & 0 deletions provisioner/terraform/executor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,10 @@ func (e *executor) execParseJSON(ctx, killCtx context.Context, args, env []strin
cmd.Stdout = out
cmd.Stderr = stdErr

e.server.logger.Debug(ctx, "executing terraform command with JSON result",
slog.F("binary_path", e.binaryPath),
slog.F("args", args),
)
err := cmd.Start()
if err != nil {
return err
Expand Down Expand Up @@ -348,6 +352,10 @@ func (e *executor) graph(ctx, killCtx context.Context) (string, error) {
cmd.Dir = e.workdir
cmd.Env = e.basicEnv()

e.server.logger.Debug(ctx, "executing terraform command graph",
slog.F("binary_path", e.binaryPath),
slog.F("args", "graph"),
)
err := cmd.Start()
if err != nil {
return "", err
Expand Down
13 changes: 12 additions & 1 deletion provisioner/terraform/provision_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ import (
"runtime"
"sort"
"strings"
"syscall"
"testing"
"time"

Expand Down Expand Up @@ -165,8 +166,18 @@ func TestProvision_Cancel(t *testing.T) {

// Example: exec /path/to/terrafork_fake_cancel.sh 1.2.1 apply "$@"
content := fmt.Sprintf("#!/bin/sh\nexec %q %s %s \"$@\"\n", fakeBin, terraform.TerraformVersion.String(), tt.mode)
err := os.WriteFile(binPath, []byte(content), 0o755) //#nosec

// golang's standard OS library can sometimes leave the file descriptor open even after
// "Closing" the file (which can then lead to a "text file busy" error, so we bypass this
// and use syscall directly).
Comment on lines +170 to +172
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Is this a known / documented issue in the stdlib?
Would be nice to remove this workaround if it gets fixed in a later version.

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TBH, I think what's supposed to happen is that it only leaves the fd open if there is some pending I/O, like on another goroutine, which wouldn't apply here. But, behavior is different on different OSes, so it's hard to be sure, and I'm at a loss for another explanation of "text file busy".

I figured since we don't need any non-blocking IO or polling, it would be better to just simplify the syscalls we make, and see if we still see the flake.

fd, err := syscall.Open(binPath, syscall.O_WRONLY|syscall.O_CREAT, 0o755)
require.NoError(t, err)
n, err := syscall.Write(fd, []byte(content))
require.NoError(t, err)
require.Equal(t, len(content), n)
err = syscall.Close(fd)
require.NoError(t, err)
t.Logf("wrote fake terraform script to %s", binPath)

ctx, api := setupProvisioner(t, &provisionerServeOptions{
binaryPath: binPath,
Expand Down