vole
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A free and open-source forge that lives in your Git repo.
Run CI jobs in a container chosen by the runner
7da9111ecabb236d48fc48592cd3d1d45f9afe78 · Keenan Nemetz · 15d ago · parent 474a812d
Run CI jobs in a container chosen by the runner Each lease gets a disposable checkout and, when --image is set, its own container from that image. The runner keeps the SSH key and trusted Git cache outside the job, so workflow code cannot reach either; older caches are rebuilt because a previous job may have written to them. The record names the image and runtime, and the queue mirrors them for the run page. Without --image the runner still executes on the host and says so.
ci/agent/worktree.go +158
| @@ -0,0 +1,158 @@ | |||
| 1 | package agent | ||
| 2 | |||
| 3 | // A job gets a disposable checkout, and the runner keeps a trusted clone beside it. | ||
| 4 | // | ||
| 5 | // The workflow may edit anything in the job tree, including its .git directory, so | ||
| 6 | // the host must never run Git from that tree after the steps finish. The record and | ||
| 7 | // site pushes use the trusted cache, which is never mounted into the container. The | ||
| 8 | // job tree is a clone of that cache with its own .git, so builds that use Git history | ||
| 9 | // still work, and a poisoned hook dies with the job. | ||
| 10 | |||
| 11 | import ( | ||
| 12 | "fmt" | ||
| 13 | "os" | ||
| 14 | "os/exec" | ||
| 15 | "path/filepath" | ||
| 16 | "strconv" | ||
| 17 | "strings" | ||
| 18 | "time" | ||
| 19 | |||
| 20 | "github.com/rodent-software/vole/client" | ||
| 21 | ) | ||
| 22 | |||
| 23 | // cacheMarker says the cache was created by a runner that never gave the job | ||
| 24 | // access to it. A cache without the marker predates disposable job trees and may | ||
| 25 | // have hooks or config written by a workflow, so it is rebuilt instead of trusted. | ||
| 26 | const cacheMarker = ".vole-trusted-cache" | ||
| 27 | |||
| 28 | type checkout struct { | ||
| 29 | // Work is the disposable tree the steps run in and the container mounts. It is | ||
| 30 | // removed when the job ends. | ||
| 31 | Work string | ||
| 32 | // GitDir is the trusted cache's git directory. It is used only by the runner | ||
| 33 | // process, never mounted into the job, and survives between jobs. | ||
| 34 | GitDir string | ||
| 35 | } | ||
| 36 | |||
| 37 | func (c checkout) cleanup() { | ||
| 38 | _ = os.RemoveAll(c.Work) | ||
| 39 | } | ||
| 40 | |||
| 41 | // cleanupJobTrees removes job trees left by a crashed runner. It is age-based so a | ||
| 42 | // second runner sharing the same --dir cannot delete work another process is using. | ||
| 43 | func cleanupJobTrees(cache string) { | ||
| 44 | root := filepath.Join(cache, "jobs") | ||
| 45 | entries, err := os.ReadDir(root) | ||
| 46 | if err != nil { | ||
| 47 | return | ||
| 48 | } | ||
| 49 | cutoff := time.Now().Add(-7 * 24 * time.Hour) | ||
| 50 | for _, e := range entries { | ||
| 51 | if !e.IsDir() { | ||
| 52 | continue | ||
| 53 | } | ||
| 54 | info, err := e.Info() | ||
| 55 | if err == nil && info.ModTime().Before(cutoff) { | ||
| 56 | _ = os.RemoveAll(filepath.Join(root, e.Name())) | ||
| 57 | } | ||
| 58 | } | ||
| 59 | } | ||
| 60 | |||
| 61 | // prepareWorktree fetches the exact commit into the trusted cache, then makes a | ||
| 62 | // disposable clone for the job. The cache is updated but never checked out for the | ||
| 63 | // job; its .git is what the record push uses. | ||
| 64 | func prepareWorktree(remote, cache, repo, sha, runID string, attempt int) (checkout, error) { | ||
| 65 | cloneURL, err := client.RepoURL(remote, repo) | ||
| 66 | if err != nil { | ||
| 67 | return checkout{}, err | ||
| 68 | } | ||
| 69 | cacheDir := filepath.Join(cache, repo) | ||
| 70 | |||
| 71 | _, gitErr := os.Stat(filepath.Join(cacheDir, ".git")) | ||
| 72 | _, markerErr := os.Stat(filepath.Join(cacheDir, cacheMarker)) | ||
| 73 | if gitErr != nil || markerErr != nil { | ||
| 74 | if err := os.RemoveAll(cacheDir); err != nil { | ||
| 75 | return checkout{}, err | ||
| 76 | } | ||
| 77 | if err := os.MkdirAll(filepath.Dir(cacheDir), 0o755); err != nil { | ||
| 78 | return checkout{}, err | ||
| 79 | } | ||
| 80 | cmd := exec.Command("git", "clone", "--quiet", cloneURL, cacheDir) | ||
| 81 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 82 | return checkout{}, fmt.Errorf("git clone: %v: %s", err, out) | ||
| 83 | } | ||
| 84 | } else { | ||
| 85 | cmd := exec.Command("git", "-C", cacheDir, "fetch", "--quiet", "--prune", "--tags", | ||
| 86 | "origin", "+refs/heads/*:refs/remotes/origin/*") | ||
| 87 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 88 | return checkout{}, fmt.Errorf("git fetch: %v: %s", err, out) | ||
| 89 | } | ||
| 90 | } | ||
| 91 | if err := os.WriteFile(filepath.Join(cacheDir, cacheMarker), []byte("1\n"), 0o644); err != nil { | ||
| 92 | return checkout{}, fmt.Errorf("mark the trusted cache: %w", err) | ||
| 93 | } | ||
| 94 | |||
| 95 | if !hasCommit(cacheDir, sha) { | ||
| 96 | cmd := exec.Command("git", "-C", cacheDir, "fetch", "--quiet", "origin", sha) | ||
| 97 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 98 | return checkout{}, fmt.Errorf("git fetch %s: %v: %s", sha, err, out) | ||
| 99 | } | ||
| 100 | } | ||
| 101 | if !hasCommit(cacheDir, sha) { | ||
| 102 | return checkout{}, fmt.Errorf("the cache does not have commit %s after fetching it", sha) | ||
| 103 | } | ||
| 104 | // A commit fetched by id may not be on a branch, and a local clone only copies | ||
| 105 | // reachable objects. A temporary ref makes it reachable for the job clone; the | ||
| 106 | // ref lives in the trusted cache and is removed before the job runs. | ||
| 107 | jobRef := "refs/vole/jobs/" + runID + "-" + strconv.Itoa(attempt) | ||
| 108 | if out, err := exec.Command("git", "-C", cacheDir, "update-ref", jobRef, sha).CombinedOutput(); err != nil { | ||
| 109 | return checkout{}, fmt.Errorf("git update-ref %s: %v: %s", jobRef, err, out) | ||
| 110 | } | ||
| 111 | defer func() { | ||
| 112 | _ = exec.Command("git", "-C", cacheDir, "update-ref", "-d", jobRef).Run() | ||
| 113 | }() | ||
| 114 | |||
| 115 | gitDir, err := client.GitDirOf(cacheDir) | ||
| 116 | if err != nil { | ||
| 117 | return checkout{}, err | ||
| 118 | } | ||
| 119 | |||
| 120 | jobDir := filepath.Join(cache, "jobs", repo, runID+"-"+strconv.Itoa(attempt)) | ||
| 121 | if err := os.MkdirAll(filepath.Dir(jobDir), 0o755); err != nil { | ||
| 122 | return checkout{}, err | ||
| 123 | } | ||
| 124 | if err := os.RemoveAll(jobDir); err != nil { | ||
| 125 | return checkout{}, err | ||
| 126 | } | ||
| 127 | cmd := exec.Command("git", "clone", "--quiet", "--no-hardlinks", cacheDir, jobDir) | ||
| 128 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 129 | return checkout{}, fmt.Errorf("git clone the job tree: %v: %s", err, out) | ||
| 130 | } | ||
| 131 | // The local clone may not carry a commit that is not on a branch. Fetch the | ||
| 132 | // temporary ref from the cache before pointing origin at the server, which the | ||
| 133 | // job cannot reach without the runner's key. | ||
| 134 | if !hasCommit(jobDir, sha) { | ||
| 135 | cmd := exec.Command("git", "-C", jobDir, "fetch", "--quiet", "origin", jobRef) | ||
| 136 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 137 | _ = os.RemoveAll(jobDir) | ||
| 138 | return checkout{}, fmt.Errorf("git fetch the job tree: %v: %s", err, out) | ||
| 139 | } | ||
| 140 | } | ||
| 141 | _ = exec.Command("git", "-C", jobDir, "remote", "set-url", "origin", cloneURL).Run() | ||
| 142 | |||
| 143 | for _, args := range [][]string{ | ||
| 144 | {"checkout", "--quiet", "--force", "--detach", sha}, | ||
| 145 | {"clean", "-qffdx"}, | ||
| 146 | } { | ||
| 147 | cmd := exec.Command("git", append([]string{"-C", jobDir}, args...)...) | ||
| 148 | if out, err := cmd.CombinedOutput(); err != nil { | ||
| 149 | _ = os.RemoveAll(jobDir) | ||
| 150 | return checkout{}, fmt.Errorf("git %s: %v: %s", strings.Join(args, " "), err, out) | ||
| 151 | } | ||
| 152 | } | ||
| 153 | return checkout{Work: jobDir, GitDir: gitDir}, nil | ||
| 154 | } | ||
| 155 | |||
| 156 | func hasCommit(dir, sha string) bool { | ||
| 157 | return exec.Command("git", "-C", dir, "cat-file", "-e", sha+"^{commit}").Run() == nil | ||
| 158 | } | ||