alice.pds.demo.boltless.dev
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1package microvm
2
3import (
4 "context"
5 "crypto/rand"
6 "encoding/binary"
7 "errors"
8 "fmt"
9 "io"
10 "log/slog"
11 "maps"
12 "math"
13 "net"
14 "os"
15 "os/exec"
16 "path/filepath"
17 "regexp"
18 "slices"
19 "strings"
20 "sync/atomic"
21 "time"
22
23 "tangled.org/core/spindle/models"
24)
25
26const (
27 minGuestCID = 3
28 vmCrashLogTailBytes = 4096
29)
30
31func AllocateCID() (uint32, error) {
32 var data [4]byte
33 if _, err := rand.Read(data[:]); err != nil {
34 return 0, fmt.Errorf("allocate guest CID: %w", err)
35 }
36 return minGuestCID + binary.BigEndian.Uint32(data[:])%60000, nil
37}
38
39func prepareWorkDir(workDir string) error {
40 if workDir == "" {
41 return fmt.Errorf("microvm work directory is required")
42 }
43 if err := os.MkdirAll(workDir, 0o755); err != nil {
44 return fmt.Errorf("create microvm work directory: %w", err)
45 }
46 return nil
47}
48
49func prepareVolumes(ctx context.Context, workDir string, volumes []Volume, mkfsExt4 string) (map[string]string, error) {
50 paths := make(map[string]string, len(volumes))
51 for _, volume := range volumes {
52 if volume.ReadOnly {
53 return nil, fmt.Errorf("read-only microvm volume %q is not supported yet", volume.Image)
54 }
55 if volume.FSType != "ext4" {
56 return nil, fmt.Errorf("microvm volume %q uses unsupported fsType %q", volume.Image, volume.FSType)
57 }
58 if volume.ImageType != "" && volume.ImageType != "raw" {
59 return nil, fmt.Errorf("microvm volume %q uses unsupported imageType %q", volume.Image, volume.ImageType)
60 }
61
62 path := filepath.Join(workDir, filepath.Base(volume.Image))
63 if err := createSparseFile(path, volume.SizeMiB); err != nil {
64 return nil, err
65 }
66 noJournal := volume.MountPoint == "/workspace"
67 if err := runMkfsExt4(ctx, mkfsExt4, path, noJournal); err != nil {
68 return nil, err
69 }
70 paths[volume.Image] = path
71 }
72 return paths, nil
73}
74
75func createSparseFile(path string, sizeMiB int64) error {
76 if sizeMiB <= 0 {
77 return fmt.Errorf("sparse file %q size must be positive", path)
78 }
79 if sizeMiB > math.MaxInt64/(1024*1024) {
80 return fmt.Errorf("sparse file %q size is too large", path)
81 }
82 file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0o600)
83 if err != nil {
84 return fmt.Errorf("create sparse file %q: %w", path, err)
85 }
86 defer file.Close()
87
88 if err := file.Truncate(sizeMiB * 1024 * 1024); err != nil {
89 return fmt.Errorf("resize sparse file %q: %w", path, err)
90 }
91 return nil
92}
93
94func runMkfsExt4(ctx context.Context, mkfsExt4, path string, noJournal bool) error {
95 if mkfsExt4 == "" {
96 return fmt.Errorf("mkfs.ext4 path is required")
97 }
98 args := []string{"-F"}
99 if noJournal {
100 args = append(args, "-O", "^has_journal")
101 }
102 args = append(args, path)
103
104 cmd := exec.CommandContext(ctx, mkfsExt4, args...)
105 output, err := cmd.CombinedOutput()
106 if err != nil {
107 return fmt.Errorf("mkfs.ext4 %q: %w: %s", path, err, strings.TrimSpace(string(output)))
108 }
109 return nil
110}
111
112func createParentedFile(path string) (*os.File, error) {
113 if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
114 return nil, fmt.Errorf("create log directory: %w", err)
115 }
116 file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
117 if err != nil {
118 return nil, fmt.Errorf("create log file %q: %w", path, err)
119 }
120 return file, nil
121}
122
123type VMLogs struct {
124 Serial string
125 Extra map[string]string
126}
127
128type VMHandle interface {
129 Shutdown(ctx context.Context) error
130 WaitContext(ctx context.Context) error
131 Close() error
132 Logs() VMLogs
133 CID() uint32
134 WorkDir() string
135 OOMKilled() bool
136}
137
138type VMConfig struct {
139 Image ImageSpec
140 CID uint32
141 EnableKVM bool
142 WorkDir string
143 Cgroup CgroupLimits
144
145 BootTimeout time.Duration
146 MkfsExt4 string
147 Dev bool
148}
149
150type workflowState struct {
151 ImageSpec ImageSpec
152 ImageSpecPath string
153 Config manifestConfig
154 ConfigKey string
155 Image string
156 CacheReadURLs []string
157 CacheTrustedPublicKeys []string
158 VM VMHandle
159 Agent *AgentSession
160 ReadCache *ReadCacheProxy
161 UploadCache *UploadCacheProxy
162 DNSProxy *DNSProxy
163 WorkDir string
164 NixOSToplevelCache nixosToplevelCacheStore
165}
166
167func (e *Engine) cleanupState(ctx context.Context, wid models.WorkflowId, state *workflowState) error {
168 if state == nil {
169 return nil
170 }
171
172 ctx = context.WithoutCancel(ctx)
173
174 var err error
175 // todo(dawn): expose this error to the user as a warning
176 if drainErr := e.drainNixCache(ctx, state); drainErr != nil {
177 e.l.Warn("cache drain failed during cleanup; continuing", "workflow", wid, "error", drainErr)
178 }
179 err = errors.Join(err, e.shutdownVM(ctx, wid, state))
180 err = errors.Join(err, closeIO(&state.Agent))
181 err = errors.Join(err, closeIO(&state.ReadCache))
182 err = errors.Join(err, closeIO(&state.UploadCache))
183 err = errors.Join(err, closeIO(&state.DNSProxy))
184 err = errors.Join(err, removeWorkDir(state))
185 return err
186}
187
188func (e *Engine) drainNixCache(ctx context.Context, state *workflowState) error {
189 if e.cfg.NixCache.UploadURL == "" {
190 return nil
191 }
192
193 drainCtx, cancel := context.WithTimeout(ctx, cacheDrainTimeout)
194 defer cancel()
195
196 if state.Agent != nil {
197 if _, err := state.Agent.Drain(drainCtx); err != nil {
198 return fmt.Errorf("drain guest nix cache uploads: %w", err)
199 }
200 }
201 return nil
202}
203
204func (e *Engine) shutdownVM(ctx context.Context, wid models.WorkflowId, state *workflowState) error {
205 if state.VM == nil {
206 return nil
207 }
208
209 var err error
210
211 if state.Agent != nil {
212 gracefulCtx, cancel := context.WithTimeout(ctx, vmShutdownTimeout)
213 poweredOff, poweroffErr := e.poweroffViaAgent(gracefulCtx, wid, state)
214 cancel()
215
216 err = errors.Join(err, poweroffErr)
217 if poweredOff {
218 return errors.Join(err, closeIO(&state.VM))
219 }
220 }
221
222 fallbackCtx, cancel := context.WithTimeout(ctx, vmShutdownTimeout)
223 defer cancel()
224
225 if shutdownErr := state.VM.Shutdown(fallbackCtx); shutdownErr != nil {
226 e.l.Warn("microVM shutdown fallback failed", "workflow", wid, "error", shutdownErr)
227 err = errors.Join(err, shutdownErr)
228 }
229
230 return errors.Join(err, closeIO(&state.VM))
231}
232
233func (e *Engine) poweroffViaAgent(ctx context.Context, wid models.WorkflowId, state *workflowState) (bool, error) {
234 if err := state.Agent.Poweroff(ctx); err != nil {
235 e.l.Warn("agent poweroff request failed", "workflow", wid, "error", err)
236 return false, err
237 }
238
239 if err := state.VM.WaitContext(ctx); err != nil {
240 e.l.Warn("agent poweroff did not stop microVM", "workflow", wid, "error", err)
241 return false, nil
242 }
243
244 return true, nil
245}
246
247// helper for closing io interfaces, sets to nil to prevent double-close
248func closeIO[T io.Closer](field *T) error {
249 closer := *field
250 var zero T
251 *field = zero
252 if any(closer) == any(zero) {
253 return nil
254 }
255 return closer.Close()
256}
257
258func removeWorkDir(state *workflowState) error {
259 if state.WorkDir == "" {
260 return nil
261 }
262
263 err := os.RemoveAll(state.WorkDir)
264 state.WorkDir = ""
265 return err
266}
267
268// returns a context derived from ctx that is cancelled either when ctx itself
269// is cancelled or when the microVM exits on its own. the returned flag reports
270// whether the VM exited (as opposed to ctx being cancelled for another reason,
271// e.g. the workflow timeout), letting callers tell a crash apart from a
272// timeout. cancel must be called to release the watcher goroutine.
273func watchVMExit(ctx context.Context, vm VMHandle) (context.Context, *atomic.Bool, context.CancelFunc) {
274 exited := &atomic.Bool{}
275 watchCtx, cancel := context.WithCancel(ctx)
276 if vm == nil {
277 return watchCtx, exited, cancel
278 }
279 go func() {
280 _ = vm.WaitContext(watchCtx) // returns when VM exits or watchCtx is cancelled
281 if watchCtx.Err() == nil {
282 exited.Store(true)
283 cancel() // don't forget to cancel the watchCtx...
284 }
285 }()
286 return watchCtx, exited, cancel
287}
288
289func VMCrashLog(vm VMHandle) string {
290 if vm == nil {
291 return ""
292 }
293 logs := vm.Logs()
294
295 var b strings.Builder
296 if tail := tailFile(logs.Serial, vmCrashLogTailBytes); tail != "" {
297 fmt.Fprintf(&b, "==== serial log ====\n%s\n", tail)
298 }
299 for _, name := range slices.Sorted(maps.Keys(logs.Extra)) {
300 if tail := tailFile(logs.Extra[name], vmCrashLogTailBytes); tail != "" {
301 fmt.Fprintf(&b, "==== %s log ====\n%s\n", name, tail)
302 }
303 }
304 return strings.TrimRight(b.String(), "\n")
305}
306
307func tailFile(path string, max int64) string {
308 if path == "" {
309 return ""
310 }
311 f, err := os.Open(path)
312 if err != nil {
313 return ""
314 }
315 defer f.Close()
316 if info, err := f.Stat(); err == nil && info.Size() > max {
317 if _, err := f.Seek(-max, io.SeekEnd); err != nil {
318 return ""
319 }
320 }
321 data, err := io.ReadAll(f)
322 if err != nil {
323 return ""
324 }
325 return strings.TrimSpace(string(data))
326}
327
328func waitAgentConn(ctx context.Context, connCh <-chan net.Conn) (net.Conn, error) {
329 select {
330 case conn := <-connCh:
331 if conn == nil {
332 return nil, fmt.Errorf("agent connection closed before setup")
333 }
334 return conn, nil
335 case <-ctx.Done():
336 return nil, fmt.Errorf("waiting for agent: %w", ctx.Err())
337 }
338}
339
340func StartVM(ctx context.Context, cfg VMConfig, logger *slog.Logger) (VMHandle, error) {
341 if logger == nil {
342 logger = slog.Default()
343 }
344
345 runner, err := runnerFor(cfg.Image.RunnerType)
346 if err != nil {
347 return nil, err
348 }
349 if err := cfg.Image.Validate(); err != nil {
350 return nil, err
351 }
352 if err := cfg.Image.validateImageFiles(); err != nil {
353 return nil, err
354 }
355 if err := runner.Validate(cfg.Image, cfg.EnableKVM); err != nil {
356 return nil, err
357 }
358
359 if err := prepareWorkDir(cfg.WorkDir); err != nil {
360 return nil, err
361 }
362
363 mkfsExt4 := cfg.MkfsExt4
364 if mkfsExt4 == "" {
365 mkfsExt4, err = exec.LookPath("mkfs.ext4")
366 if err != nil {
367 return nil, fmt.Errorf("mkfs.ext4 command not found in PATH: %w", err)
368 }
369 }
370 volumePaths, err := prepareVolumes(ctx, cfg.WorkDir, cfg.Image.Volumes, mkfsExt4)
371 if err != nil {
372 return nil, err
373 }
374
375 return runner.Start(ctx, cfg, volumePaths, logger)
376}
377
378// checks serial log for ooms or kernel panic
379// this is very linux specific! but these strings are stable in linux itself, see mm/oom_kill.c and kernel/panic.c
380func ParseCrashLog(detail string) (error, bool) {
381 if strings.Contains(detail, "Out of memory:") {
382 // we can show process name where possible
383 re := regexp.MustCompile(`Out of memory: Killed process \d+ \(([^)]+)\)`)
384 matches := re.FindStringSubmatch(detail)
385 if len(matches) > 1 {
386 return fmt.Errorf("guest out of memory (process '%s' killed by guest kernel OOM)", matches[1]), true
387 }
388 return errors.New("guest out of memory (OOM killer invoked)"), true
389 }
390 if strings.Contains(detail, "Kernel panic") {
391 return errors.New("guest kernel panic"), true
392 }
393 return nil, false
394}