-
Notifications
You must be signed in to change notification settings - Fork 54
/
state.go
601 lines (531 loc) · 16.6 KB
/
state.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
// Copyright (c) 2024 Canonical Ltd
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 3 as
// published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
// Package state implements the representation of system state.
package state
import (
"encoding/json"
"errors"
"fmt"
"io"
"sort"
"strconv"
"sync"
"sync/atomic"
"time"
"github.com/canonical/pebble/internals/logger"
)
// A Backend is used by State to checkpoint on every unlock operation
// and to mediate requests to ensure the state sooner or request restarts.
type Backend interface {
Checkpoint(data []byte) error
EnsureBefore(d time.Duration)
}
type customData map[string]*json.RawMessage
func (data customData) get(key string, value interface{}) error {
entryJSON := data[key]
if entryJSON == nil {
return &NoStateError{Key: key}
}
err := json.Unmarshal(*entryJSON, value)
if err != nil {
return fmt.Errorf("internal error: could not unmarshal state entry %q: %v", key, err)
}
return nil
}
func (data customData) has(key string) bool {
return data[key] != nil
}
func (data customData) set(key string, value interface{}) {
if value == nil {
delete(data, key)
return
}
serialized, err := json.Marshal(value)
if err != nil {
logger.Panicf("internal error: could not marshal value for state entry %q: %v", key, err)
}
entryJSON := json.RawMessage(serialized)
data[key] = &entryJSON
}
// State represents an evolving system state that persists across restarts.
//
// The State is concurrency-safe, and all reads and writes to it must be
// performed with the state locked. It's a runtime error (panic) to perform
// operations without it.
//
// The state is persisted on every unlock operation via the StateBackend
// it was initialized with.
type State struct {
mu sync.Mutex
muC int32
lastTaskId int
lastChangeId int
lastLaneId int
lastNoticeId int
// lastHandlerId is not serialized, it's only used during runtime
// for registering runtime callbacks
lastHandlerId int
backend Backend
data customData
changes map[string]*Change
tasks map[string]*Task
warnings map[string]*Warning
notices map[noticeKey]*Notice
noticeCond *sync.Cond
modified bool
cache map[interface{}]interface{}
pendingChangeByAttr map[string]func(*Change) bool
// task/changes observing
taskHandlers map[int]func(t *Task, old, new Status)
changeHandlers map[int]func(chg *Change, old, new Status)
}
// New returns a new empty state.
func New(backend Backend) *State {
st := &State{
backend: backend,
data: make(customData),
changes: make(map[string]*Change),
tasks: make(map[string]*Task),
warnings: make(map[string]*Warning),
notices: make(map[noticeKey]*Notice),
modified: true,
cache: make(map[interface{}]interface{}),
pendingChangeByAttr: make(map[string]func(*Change) bool),
taskHandlers: make(map[int]func(t *Task, old Status, new Status)),
changeHandlers: make(map[int]func(chg *Change, old Status, new Status)),
}
st.noticeCond = sync.NewCond(st) // use State.Lock and State.Unlock
return st
}
// Modified returns whether the state was modified since the last checkpoint.
func (s *State) Modified() bool {
return s.modified
}
// Lock acquires the state lock.
func (s *State) Lock() {
s.mu.Lock()
atomic.AddInt32(&s.muC, 1)
}
func (s *State) reading() {
if atomic.LoadInt32(&s.muC) != 1 {
panic("internal error: accessing state without lock")
}
}
func (s *State) writing() {
s.modified = true
if atomic.LoadInt32(&s.muC) != 1 {
panic("internal error: accessing state without lock")
}
}
func (s *State) unlock() {
atomic.AddInt32(&s.muC, -1)
s.mu.Unlock()
}
type marshalledState struct {
Data map[string]*json.RawMessage `json:"data"`
Changes map[string]*Change `json:"changes"`
Tasks map[string]*Task `json:"tasks"`
Warnings []*Warning `json:"warnings,omitempty"`
Notices []*Notice `json:"notices,omitempty"`
LastChangeId int `json:"last-change-id"`
LastTaskId int `json:"last-task-id"`
LastLaneId int `json:"last-lane-id"`
LastNoticeId int `json:"last-notice-id"`
}
// MarshalJSON makes State a json.Marshaller
func (s *State) MarshalJSON() ([]byte, error) {
s.reading()
return json.Marshal(marshalledState{
Data: s.data,
Changes: s.changes,
Tasks: s.tasks,
Warnings: s.flattenWarnings(),
Notices: s.flattenNotices(nil),
LastTaskId: s.lastTaskId,
LastChangeId: s.lastChangeId,
LastLaneId: s.lastLaneId,
LastNoticeId: s.lastNoticeId,
})
}
// UnmarshalJSON makes State a json.Unmarshaller
func (s *State) UnmarshalJSON(data []byte) error {
s.writing()
var unmarshalled marshalledState
err := json.Unmarshal(data, &unmarshalled)
if err != nil {
return err
}
s.data = unmarshalled.Data
s.changes = unmarshalled.Changes
s.tasks = unmarshalled.Tasks
s.unflattenWarnings(unmarshalled.Warnings)
s.unflattenNotices(unmarshalled.Notices)
s.lastChangeId = unmarshalled.LastChangeId
s.lastTaskId = unmarshalled.LastTaskId
s.lastLaneId = unmarshalled.LastLaneId
s.lastNoticeId = unmarshalled.LastNoticeId
// backlink state again
for _, t := range s.tasks {
t.state = s
}
for _, chg := range s.changes {
chg.state = s
chg.finishUnmarshal()
}
return nil
}
func (s *State) checkpointData() []byte {
data, err := json.Marshal(s)
if err != nil {
// this shouldn't happen, because the actual delicate serializing happens at various Set()s
logger.Panicf("internal error: could not marshal state for checkpointing: %v", err)
}
return data
}
// unlock checkpoint retry parameters (5 mins of retries by default)
var (
unlockCheckpointRetryMaxTime = 5 * time.Minute
unlockCheckpointRetryInterval = 3 * time.Second
)
// Unlocker returns a closure that will unlock and checkpoint the state and
// in turn return a function to relock it.
func (s *State) Unlocker() (unlock func() (relock func())) {
return func() func() {
s.Unlock()
return s.Lock
}
}
// Unlock releases the state lock and checkpoints the state.
// It does not return until the state is correctly checkpointed.
// After too many unsuccessful checkpoint attempts, it panics.
func (s *State) Unlock() {
defer s.unlock()
if !s.modified || s.backend == nil {
return
}
data := s.checkpointData()
var err error
start := time.Now()
for time.Since(start) <= unlockCheckpointRetryMaxTime {
if err = s.backend.Checkpoint(data); err == nil {
s.modified = false
return
}
time.Sleep(unlockCheckpointRetryInterval)
}
logger.Panicf("cannot checkpoint even after %v of retries every %v: %v", unlockCheckpointRetryMaxTime, unlockCheckpointRetryInterval, err)
}
// EnsureBefore asks for an ensure pass to happen sooner within duration from now.
func (s *State) EnsureBefore(d time.Duration) {
if s.backend != nil {
s.backend.EnsureBefore(d)
}
}
// ErrNoState represents the case of no state entry for a given key.
var ErrNoState = errors.New("no state entry for key")
// NoStateError represents the case where no state could be found for a given key.
type NoStateError struct {
// Key is the key for which no state could be found.
Key string
}
func (e *NoStateError) Error() string {
var keyMsg string
if e.Key != "" {
keyMsg = fmt.Sprintf(" %q", e.Key)
}
return fmt.Sprintf("no state entry for key%s", keyMsg)
}
// Is returns true if the error is of type *NoStateError or equal to ErrNoState.
// NoStateError's key isn't compared between errors.
func (e *NoStateError) Is(err error) bool {
_, ok := err.(*NoStateError)
return ok || errors.Is(err, ErrNoState)
}
// Get unmarshals the stored value associated with the provided key
// into the value parameter.
// It returns ErrNoState if there is no entry for key.
func (s *State) Get(key string, value interface{}) error {
s.reading()
return s.data.get(key, value)
}
// Has returns whether the provided key has an associated value.
func (s *State) Has(key string) bool {
s.reading()
return s.data.has(key)
}
// Set associates value with key for future consulting by managers.
// The provided value must properly marshal and unmarshal with encoding/json.
func (s *State) Set(key string, value interface{}) {
s.writing()
s.data.set(key, value)
}
// Cached returns the cached value associated with the provided key.
// It returns nil if there is no entry for key.
func (s *State) Cached(key interface{}) interface{} {
s.reading()
return s.cache[key]
}
// Cache associates value with key for future consulting by managers.
// The cached value is not persisted.
func (s *State) Cache(key, value interface{}) {
s.reading() // Doesn't touch persisted data.
if value == nil {
delete(s.cache, key)
} else {
s.cache[key] = value
}
}
// NewChange adds a new change to the state.
func (s *State) NewChange(kind, summary string) *Change {
s.writing()
s.lastChangeId++
id := strconv.Itoa(s.lastChangeId)
chg := newChange(s, id, kind, summary)
s.changes[id] = chg
// Add change-update notice for newly spawned change
// NOTE: Implies State.writing()
if err := chg.addNotice(); err != nil {
logger.Panicf(`internal error: failed to add "change-update" notice for new change: %v`, err)
}
return chg
}
// NewLane creates a new lane in the state.
func (s *State) NewLane() int {
s.writing()
s.lastLaneId++
return s.lastLaneId
}
// Changes returns all changes currently known to the state.
func (s *State) Changes() []*Change {
s.reading()
res := make([]*Change, 0, len(s.changes))
for _, chg := range s.changes {
res = append(res, chg)
}
return res
}
// Change returns the change for the given ID.
func (s *State) Change(id string) *Change {
s.reading()
return s.changes[id]
}
// NewTask creates a new task.
// It usually will be registered with a Change using AddTask or
// through a TaskSet.
func (s *State) NewTask(kind, summary string) *Task {
s.writing()
s.lastTaskId++
id := strconv.Itoa(s.lastTaskId)
t := newTask(s, id, kind, summary)
s.tasks[id] = t
return t
}
// Tasks returns all tasks currently known to the state and linked to changes.
func (s *State) Tasks() []*Task {
s.reading()
res := make([]*Task, 0, len(s.tasks))
for _, t := range s.tasks {
if t.Change() == nil { // skip unlinked tasks
continue
}
res = append(res, t)
}
return res
}
// Task returns the task for the given ID if the task has been linked to a change.
func (s *State) Task(id string) *Task {
s.reading()
t := s.tasks[id]
if t == nil || t.Change() == nil {
return nil
}
return t
}
// TaskCount returns the number of tasks that currently exist in the state,
// whether linked to a change or not.
func (s *State) TaskCount() int {
s.reading()
return len(s.tasks)
}
func (s *State) tasksIn(tids []string) []*Task {
res := make([]*Task, len(tids))
for i, tid := range tids {
res[i] = s.tasks[tid]
}
return res
}
// RegisterPendingChangeByAttr registers predicates that will be invoked by
// Prune on changes with the specified attribute set to check whether even if
// they meet the time criteria they must not be aborted yet.
func (s *State) RegisterPendingChangeByAttr(attr string, f func(*Change) bool) {
s.pendingChangeByAttr[attr] = f
}
// Prune does several cleanup tasks to the in-memory state:
//
// - it removes changes that became ready for more than pruneWait and aborts
// tasks spawned for more than abortWait unless prevented by predicates
// registered with RegisterPendingChangeByAttr.
//
// - it removes tasks unlinked to changes after pruneWait. When there are more
// changes than the limit set via "maxReadyChanges" those changes in ready
// state will also removed even if they are below the pruneWait duration.
//
// - it removes expired warnings and notices.
func (s *State) Prune(startOfOperation time.Time, pruneWait, abortWait time.Duration, maxReadyChanges int) {
now := time.Now()
pruneLimit := now.Add(-pruneWait)
abortLimit := now.Add(-abortWait)
// sort from oldest to newest
changes := s.Changes()
sort.Sort(byReadyTime(changes))
readyChangesCount := 0
for i := range changes {
// changes are sorted (not-ready sorts first)
// so we know we can iterate in reverse and break once we
// find a ready time of "zero"
chg := changes[len(changes)-i-1]
if chg.ReadyTime().IsZero() {
break
}
readyChangesCount++
}
for k, w := range s.warnings {
if w.ExpiredBefore(now) {
delete(s.warnings, k)
}
}
for k, n := range s.notices {
if n.expired(now) {
delete(s.notices, k)
}
}
NextChange:
for _, chg := range changes {
readyTime := chg.ReadyTime()
spawnTime := chg.SpawnTime()
if spawnTime.Before(startOfOperation) {
spawnTime = startOfOperation
}
if readyTime.IsZero() {
if spawnTime.Before(pruneLimit) && len(chg.Tasks()) == 0 {
chg.Abort()
delete(s.changes, chg.ID())
} else if spawnTime.Before(abortLimit) {
for attr, pending := range s.pendingChangeByAttr {
if chg.Has(attr) && pending(chg) {
continue NextChange
}
}
chg.AbortUnreadyLanes()
}
continue
}
// change old or we have too many changes
if readyTime.Before(pruneLimit) || readyChangesCount > maxReadyChanges {
s.writing()
for _, t := range chg.Tasks() {
delete(s.tasks, t.ID())
}
delete(s.changes, chg.ID())
readyChangesCount--
}
}
for tid, t := range s.tasks {
// TODO: this could be done more aggressively
if t.Change() == nil && t.SpawnTime().Before(pruneLimit) {
s.writing()
delete(s.tasks, tid)
}
}
}
// GetMaybeTimings implements timings.GetSaver
func (s *State) GetMaybeTimings(timings interface{}) error {
if err := s.Get("timings", timings); err != nil && !errors.Is(err, ErrNoState) {
return err
}
return nil
}
// AddTaskStatusChangedHandler adds a callback function that will be invoked
// whenever tasks change status.
// NOTE: Callbacks registered this way may be invoked in the context
// of the taskrunner, so the callbacks should be as simple as possible, and return
// as quickly as possible, and should avoid the use of i/o code or blocking, as this
// will stop the entire task system.
func (s *State) AddTaskStatusChangedHandler(f func(t *Task, old, new Status)) (id int) {
// We are reading here as we want to ensure access to the state is serialized,
// and not writing as we are not changing the part of state that goes on the disk.
s.reading()
id = s.lastHandlerId
s.lastHandlerId++
s.taskHandlers[id] = f
return id
}
func (s *State) RemoveTaskStatusChangedHandler(id int) {
s.reading()
delete(s.taskHandlers, id)
}
func (s *State) notifyTaskStatusChangedHandlers(t *Task, old, new Status) {
s.reading()
for _, f := range s.taskHandlers {
f(t, old, new)
}
}
// AddChangeStatusChangedHandler adds a callback function that will be invoked
// whenever a Change changes status.
// NOTE: Callbacks registered this way may be invoked in the context
// of the taskrunner, so the callbacks should be as simple as possible, and return
// as quickly as possible, and should avoid the use of i/o code or blocking, as this
// will stop the entire task system.
func (s *State) AddChangeStatusChangedHandler(f func(chg *Change, old, new Status)) (id int) {
// We are reading here as we want to ensure access to the state is serialized,
// and not writing as we are not changing the part of state that goes on the disk.
s.reading()
id = s.lastHandlerId
s.lastHandlerId++
s.changeHandlers[id] = f
return id
}
func (s *State) RemoveChangeStatusChangedHandler(id int) {
s.reading()
delete(s.changeHandlers, id)
}
func (s *State) notifyChangeStatusChangedHandlers(chg *Change, old, new Status) {
s.reading()
for _, f := range s.changeHandlers {
f(chg, old, new)
}
}
// SaveTimings implements timings.GetSaver
func (s *State) SaveTimings(timings interface{}) {
s.Set("timings", timings)
}
// ReadState returns the state deserialized from r.
func ReadState(backend Backend, r io.Reader) (*State, error) {
s := new(State)
s.Lock()
defer s.unlock()
d := json.NewDecoder(r)
err := d.Decode(&s)
if err != nil {
return nil, fmt.Errorf("cannot read state: %s", err)
}
s.backend = backend
s.noticeCond = sync.NewCond(s)
s.modified = false
s.cache = make(map[interface{}]interface{})
s.pendingChangeByAttr = make(map[string]func(*Change) bool)
s.changeHandlers = make(map[int]func(chg *Change, old Status, new Status))
s.taskHandlers = make(map[int]func(t *Task, old Status, new Status))
return s, err
}