| 1 | package console |
| 2 | |
| 3 | import ( |
| 4 | "sync" |
| 5 | |
| 6 | "github.com/carlosframework/platform/internal/objstore" |
| 7 | ) |
| 8 | |
| 9 | // storeWalkLocks serialises the object-storage walks per app, which is what |
| 10 | // objstore has always said this package does. |
| 11 | // |
| 12 | // `deleteRecordIfUnchanged` narrows the grant-vs-teardown window and then |
| 13 | // accepts what is left of it, for a stated reason (`walk.go:560`): |
| 14 | // |
| 15 | // This narrows the window; it does not close it. A grant landing between |
| 16 | // the re-read and the Delete still loses its record, and only a CAS delete |
| 17 | // in the Store interface could fix that. The console door serialises these |
| 18 | // verbs per app, so the remaining window is a fraction of one round trip. |
| 19 | // |
| 20 | // Until this type there was no such serialisation anywhere in the console — |
| 21 | // no lock of any kind around Grant, Rotate, RotateFinish or Teardown. The |
| 22 | // premise the walks reason from was simply untrue, and the window was a whole |
| 23 | // walk wide rather than a fraction of a round trip. |
| 24 | // |
| 25 | // It mattered less than it might have because reaching it took two operators |
| 26 | // running store verbs against one app simultaneously. Self-serve object |
| 27 | // storage (#381) removes that accident: a member's own `carlos store create` |
| 28 | // drives a grant walk, and the create door's own comment says people re-run it |
| 29 | // "from a second terminal, from a deploy script" (apistore.go:176-179). |
| 30 | // |
| 31 | // IN-PROCESS ONLY, and deliberately not sold as more. One console process |
| 32 | // holds one of these, so two consoles fronting one deployment would still |
| 33 | // interleave. That residue is what the walks' CAS guards are for — Grant's |
| 34 | // step-six retry, Rotate's step-five retry, and this delete's re-read. The |
| 35 | // lock removes the ordinary race; CAS survives the exotic one. |
| 36 | // |
| 37 | // Entries are reference-counted and dropped at zero, so an app that is walked |
| 38 | // once does not hold a mutex for the life of the process. |
| 39 | type storeWalkLocks struct { |
| 40 | mu sync.Mutex |
| 41 | m map[string]*storeWalkLock |
| 42 | } |
| 43 | |
| 44 | type storeWalkLock struct { |
| 45 | mu sync.Mutex |
| 46 | refs int |
| 47 | } |
| 48 | |
| 49 | func newStoreWalkLocks() *storeWalkLocks { |
| 50 | return &storeWalkLocks{m: make(map[string]*storeWalkLock)} |
| 51 | } |
| 52 | |
| 53 | // storeWalkKey is the map's key shape, in one place because tests inspect the |
| 54 | // map to prove a second walk really queued. When the environment joined the |
| 55 | // key on 2026-09-19 the literal was restated in two test files, and both went |
| 56 | // on compiling while reading a refcount that could never move — they failed |
| 57 | // as "the waiter never registered", which is a sentence about the lock rather |
| 58 | // than about the key. Derive it here. |
| 59 | // |
| 60 | // The key is the store's IAM user name rather than the triple spelled out, |
| 61 | // because two different triples can resolve to ONE estate: app "shop" with |
| 62 | // environment "eu" and app "shop-eu" mint the same bucket and the same user |
| 63 | // (#218). objstore's name claims refuse the second of them whichever lock is |
| 64 | // held, but walks over one estate are what this lock exists to serialise, so |
| 65 | // it keys on the estate's name. |
| 66 | func storeWalkKey(acct, app, env string) string { return objstore.UserNameIn(acct, app, env) } |
| 67 | |
| 68 | // lock blocks until this store's walk lock is held, and returns the release. |
| 69 | // The caller defers it: |
| 70 | // |
| 71 | // defer s.storeWalks.lock(acct.Sqid, app, env)() |
| 72 | // |
| 73 | // The key covers the account, the app AND the environment ("" for the app's |
| 74 | // own store): two apps in one account share no estate, and since 2026-09-19 |
| 75 | // two STORES of one app share none either — a bucket, an IAM user and a |
| 76 | // config bundle each, all named for the triple (objstore's MintedBucketIn and |
| 77 | // UserNameIn). Serialising across any of them would cost concurrency and buy |
| 78 | // nothing. The one exception is triples whose joined names collide, which |
| 79 | // storeWalkKey folds into one key. |
| 80 | func (l *storeWalkLocks) lock(acct, app, env string) func() { |
| 81 | key := storeWalkKey(acct, app, env) |
| 82 | l.mu.Lock() |
| 83 | e := l.m[key] |
| 84 | if e == nil { |
| 85 | e = &storeWalkLock{} |
| 86 | l.m[key] = e |
| 87 | } |
| 88 | e.refs++ |
| 89 | l.mu.Unlock() |
| 90 | |
| 91 | e.mu.Lock() |
| 92 | return func() { |
| 93 | e.mu.Unlock() |
| 94 | l.mu.Lock() |
| 95 | e.refs-- |
| 96 | if e.refs == 0 { |
| 97 | delete(l.m, key) |
| 98 | } |
| 99 | l.mu.Unlock() |
| 100 | } |
| 101 | } |
| 102 | |
amadan