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package main
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import (
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"bytes"
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"context"
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"encoding/json"
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"errors"
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"flag"
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"fmt"
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"net/http"
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"os"
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"os/exec"
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"path/filepath"
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"runtime"
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"strconv"
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"strings"
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"time"
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// cmdRunner long-polls outward, needing no inbound port, which is what makes pasting it work.
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func cmdRunner(ctx context.Context, args []string) error {
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if len(args) == 0 {
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return errors.New("usage: forge runner <token> [--labels a,b]")
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tok := args[0]
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fs := flag.NewFlagSet("runner", flag.ContinueOnError)
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server := fs.String("server", "", "the forge to attach to")
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labels := fs.String("labels", "", "what this machine can build, comma separated")
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workdir := fs.String("workdir", "", "where to clone, defaults to a temporary directory")
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if err := fs.Parse(args[1:]); err != nil {
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return err
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base := strings.TrimRight(*server, "/")
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if base == "" {
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base = os.Getenv("BAREREPO_SERVER")
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if base == "" {
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// Appendix E's line has no flag, which works because the last attach is remembered.
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base = recallServer(tok)
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if base == "" {
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return errors.New("this token has not attached anywhere yet.\n" +
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"paste the line from the add-a-runner page, or pass --server https://barerepo.example")
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host, _ := os.Hostname()
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work := *workdir
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if work == "" {
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var err error
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if work, err = os.MkdirTemp("", "barerepo-runner-"); err != nil {
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return err
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defer os.RemoveAll(work)
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r := &runner{base: base, token: tok, work: work,
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labels: splitCSV(*labels), client: &http.Client{Timeout: 2 * time.Minute}}
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if err := r.attach(ctx, host); err != nil {
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return err
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// Remembered after it worked, so a wrong address is never the one recalled.
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rememberServer(tok, base)
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fmt.Printf("attached as %s. waiting for work.\n", host)
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for {
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if err := r.once(ctx); err != nil {
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if ctx.Err() != nil {
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return nil
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fmt.Fprintln(os.Stderr, "forge: "+err.Error())
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time.Sleep(5 * time.Second)
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type runner struct {
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base string
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token string
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work string
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labels []string
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id int64
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client *http.Client
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func (r *runner) attach(ctx context.Context, hostname string) error {
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var out struct {
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RunnerID int64 `json:"runner_id"`
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PollInterval int `json:"poll_interval"`
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err := r.post(ctx, "/runner/attach", map[string]any{
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"token": r.token, "hostname": hostname,
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"os": runtime.GOOS, "arch": runtime.GOARCH, "labels": r.labels,
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}, &out)
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if err != nil {
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return err
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r.id = out.RunnerID
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return nil
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// once polls, and builds whatever comes back.
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func (r *runner) once(ctx context.Context) error {
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req, err := http.NewRequestWithContext(ctx, http.MethodGet,
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fmt.Sprintf("%s/runner/poll?id=%d&token=%s", r.base, r.id, r.token), nil)
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if err != nil {
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return err
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}
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resp, err := r.client.Do(req)
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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if resp.StatusCode == http.StatusNoContent {
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return nil
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}
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if resp.StatusCode != http.StatusOK {
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return fmt.Errorf("poll: %s", resp.Status)
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}
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var job jobOffer
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if err := json.NewDecoder(resp.Body).Decode(&job); err != nil {
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return err
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}
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fmt.Printf("building %s at %s\n", job.Repo, short(job.SHA))
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started := time.Now()
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exit, output := r.build(ctx, job)
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if err := r.post(ctx, "/runner/log", map[string]any{
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"token": r.token, "job_id": job.JobID, "seq": 0, "chunk": output,
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}, nil); err != nil {
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return err
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}
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return r.post(ctx, "/runner/done", map[string]any{
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"token": r.token, "job_id": job.JobID,
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"exit_code": exit, "duration": int(time.Since(started).Seconds()),
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}, nil)
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// jobOffer is what a poll returns, which is everything a build needs and nothing else.
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type jobOffer struct {
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JobID int64 `json:"job_id"`
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Repo string `json:"repo"`
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Ref string `json:"ref"`
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SHA string `json:"sha"`
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Command string `json:"command"`
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Image string `json:"image"`
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CloneURL string `json:"clone_url"`
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JobToken string `json:"job_token"`
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// build clones at the commit and captures the whole output, which chapter 16 puts on one page.
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func (r *runner) build(ctx context.Context, job jobOffer) (int, string) {
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cloneURL, jobToken, sha, command := job.CloneURL, job.JobToken, job.SHA, job.Command
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dir := filepath.Join(r.work, short(sha))
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os.RemoveAll(dir)
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if err := os.MkdirAll(dir, 0o750); err != nil {
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return 1, err.Error()
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}
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var log bytes.Buffer
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withAuth := strings.Replace(cloneURL, "://", "://x:"+jobToken+"@", 1)
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// Every step runs in the clone, so the log shows the command and not a temporary path.
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steps := [][]string{
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{"git", "init", "-q"},
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{"git", "fetch", "-q", "--depth", "1", withAuth, sha},
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{"git", "checkout", "-q", "FETCH_HEAD"},
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}
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for _, step := range steps {
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shown := strings.Join(step, " ")
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fmt.Fprintf(&log, "$ %s\n", strings.ReplaceAll(shown, jobToken, "<token>"))
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cmd := exec.CommandContext(ctx, step[0], step[1:]...)
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cmd.Dir = dir
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cmd.Stdout = &log
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cmd.Stderr = &log
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if err := cmd.Run(); err != nil {
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fmt.Fprintf(&log, "%v\n", err)
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return 1, log.String()
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}
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}
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fmt.Fprintf(&log, "$ %s\n", command)
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cmd := exec.CommandContext(ctx, "sh", "-c", command)
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cmd.Dir = dir
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cmd.Stdout = &log
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cmd.Stderr = &log
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// A build attaches a release file by speaking the same plain http the runner does. Chapter 22.5.
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cmd.Env = append(os.Environ(),
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"BAREREPO_URL="+r.base,
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"BAREREPO_REPO="+job.Repo,
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"BAREREPO_JOB="+strconv.FormatInt(job.JobID, 10),
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"BAREREPO_JOB_TOKEN="+jobToken,
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)
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err := cmd.Run()
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code := 0
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if err != nil {
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code = 1
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var ee *exec.ExitError
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if errors.As(err, &ee) {
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code = ee.ExitCode()
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}
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fmt.Fprintf(&log, "$ exit %d\n", code)
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}
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return code, log.String()
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func (r *runner) post(ctx context.Context, path string, body any, out any) error {
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buf, err := json.Marshal(body)
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if err != nil {
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return err
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}
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req, err := http.NewRequestWithContext(ctx, http.MethodPost, r.base+path, bytes.NewReader(buf))
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if err != nil {
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return err
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}
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req.Header.Set("Content-Type", "application/json")
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resp, err := r.client.Do(req)
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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if resp.StatusCode >= 400 {
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msg, _ := readAll(resp.Body, 1<<12)
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return fmt.Errorf("%s: %s: %s", path, resp.Status, strings.TrimSpace(msg))
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}