| 1 | package console |
| 2 | |
| 3 | // The console's reads through the S3 change index (S3 change-index design |
| 4 | // §4.6, discussion #336). Armed only by CARLOS_CHANGE_INDEX=read, which |
| 5 | // cmd/console turns into a record view handed to SetRecordView; unarmed, |
| 6 | // recordView stays nil and every sweep walks the bucket as before. |
| 7 | |
| 8 | import ( |
| 9 | "context" |
| 10 | "log" |
| 11 | |
| 12 | "github.com/carlosframework/platform/internal/provision" |
| 13 | "github.com/carlosframework/platform/internal/release" |
| 14 | ) |
| 15 | |
| 16 | // SetRecordView arms the run and seed sweeps' record reads with v. serve |
| 17 | // calls it once, before it starts any worker; nil leaves them disarmed. |
| 18 | func (s *Server) SetRecordView(v *provision.RecordView) { s.recordView = v } |
| 19 | |
| 20 | // The viewUse states; zero is none yet. |
| 21 | const ( |
| 22 | viewUseView int32 = 1 + iota |
| 23 | viewUseWalk |
| 24 | ) |
| 25 | |
| 26 | // recordWalkStore is the store a sweep's record walk reads: the armed view's |
| 27 | // snapshot over live, refreshed first, when the refresh returned nil and the |
| 28 | // snapshot is Complete. Otherwise ok is false and the store is live, so the |
| 29 | // sweep walks the bucket as it did before the index (spec §3.4). |
| 30 | // |
| 31 | // Only record walks take it (provision.ListAllRecords*). The snapshot's |
| 32 | // ListDirs of apps/<a>/ names only apps with record-family state, so it must |
| 33 | // never reach an app enumerator, and every write and every non-record read |
| 34 | // (runs/, seeds/) stays on live. ctx bounds the refresh, so a stuck index |
| 35 | // poll or walk cannot hold the view, or the sweep, for good. |
| 36 | func (s *Server) recordWalkStore(ctx context.Context, live release.Store) (release.Store, bool) { |
| 37 | v := s.recordView |
| 38 | if v == nil || live == nil { |
| 39 | return live, false |
| 40 | } |
| 41 | err := v.Refresh(ctx) |
| 42 | sn := v.Snapshot() |
| 43 | switch { |
| 44 | case err != nil: |
| 45 | s.noteViewUse(false, "the record view's refresh failed: "+err.Error()) |
| 46 | return live, false |
| 47 | case sn == nil || !sn.Complete: |
| 48 | s.noteViewUse(false, "the record view's snapshot is incomplete") |
| 49 | return live, false |
| 50 | } |
| 51 | s.noteViewUse(true, "") |
| 52 | return sn.Store(live), true |
| 53 | } |
| 54 | |
| 55 | // noteViewUse logs a switch between reading the view and walking the bucket, |
| 56 | // once per change rather than on every pass. |
| 57 | func (s *Server) noteViewUse(ok bool, why string) { |
| 58 | state := viewUseWalk |
| 59 | if ok { |
| 60 | state = viewUseView |
| 61 | } |
| 62 | if s.viewUse.Swap(state) == state { |
| 63 | return |
| 64 | } |
| 65 | if ok { |
| 66 | log.Printf("console: record view: the sweeps' record walks read the view") |
| 67 | return |
| 68 | } |
| 69 | log.Printf("console: record view: %s; the sweeps' record walks read the bucket until it can vouch again", why) |
| 70 | } |
| 71 | |
amadan