| 1 | package rollout |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "time" |
| 6 | |
| 7 | "github.com/carlosframework/platform/internal/appconfig" |
| 8 | ) |
| 9 | |
| 10 | // configTrack is one instance's two config revisions (spec §8.1). Delivered |
| 11 | // is what config sync last wrote; active is the revision the current |
| 12 | // generation started with. They are equal at rest. |
| 13 | type configTrack struct { |
| 14 | delivered string |
| 15 | active string |
| 16 | // sleeping: the instance had no process when delivered was written |
| 17 | // (spec §8.1). Its next wake starts with that file, so no attempt is |
| 18 | // pending and the ack goes out at once, marked Hibernating. |
| 19 | sleeping bool |
| 20 | fails int |
| 21 | lastErr string |
| 22 | |
| 23 | ack *appconfig.ConfigAck |
| 24 | ackRev string |
| 25 | ackWrite func(context.Context, appconfig.ConfigAck) |
| 26 | } |
| 27 | |
| 28 | // configBackoff is the wait after the nth consecutive failed config attempt: |
| 29 | // one minute, doubling, at most thirty (spec §8.1). |
| 30 | func configBackoff(n int) time.Duration { |
| 31 | d := time.Minute |
| 32 | for i := 1; i < n && d < 30*time.Minute; i++ { |
| 33 | d *= 2 |
| 34 | } |
| 35 | return min(d, 30*time.Minute) |
| 36 | } |
| 37 | |
| 38 | // deferAck holds a config ack until the revision it was written for is |
| 39 | // active, and returns a func to run now when it already is. A route config |
| 40 | // sync never reported a delivery for (a shape the scheduler does not |
| 41 | // restart) acknowledges at once, as before. So does a sleeping instance, |
| 42 | // with today's hibernating acknowledgement: the config landed and nothing |
| 43 | // woke to run it (ConfigAck.Hibernating, "delivered on wake"). |
| 44 | func (t *configTrack) deferAck(a appconfig.ConfigAck, write func(context.Context, appconfig.ConfigAck)) func(context.Context) { |
| 45 | // A newer delivery supersedes any ack still held for an older one, whether |
| 46 | // or not this one waits: releasing the old ack later would write it after |
| 47 | // the newer ack, with a revision that is no longer delivered (spec §8.1). |
| 48 | t.ack, t.ackWrite, t.ackRev = nil, nil, "" |
| 49 | if t.sleeping { |
| 50 | a.Hibernating, a.Restarted = true, false |
| 51 | return func(ctx context.Context) { write(ctx, a) } |
| 52 | } |
| 53 | if t.delivered == "" || t.active == t.delivered { |
| 54 | return func(ctx context.Context) { write(ctx, a) } |
| 55 | } |
| 56 | t.ack, t.ackRev, t.ackWrite = &a, t.delivered, write |
| 57 | return nil |
| 58 | } |
| 59 | |
| 60 | // activate records rev as active and returns the held ack when it was |
| 61 | // waiting for exactly rev and rev is still the delivered revision. |
| 62 | func (t *configTrack) activate(rev string) (func(context.Context), bool) { |
| 63 | if rev == "" { |
| 64 | return nil, false |
| 65 | } |
| 66 | t.active = rev |
| 67 | if rev == t.delivered { |
| 68 | t.fails, t.lastErr = 0, "" |
| 69 | } |
| 70 | if t.ack == nil || t.ackRev != rev || rev != t.delivered { |
| 71 | return nil, false |
| 72 | } |
| 73 | a, write := *t.ack, t.ackWrite |
| 74 | t.ack, t.ackWrite, t.ackRev = nil, nil, "" |
| 75 | return func(ctx context.Context) { write(ctx, a) }, true |
| 76 | } |
| 77 | |
amadan