| 1 | package moves |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "errors" |
| 6 | "fmt" |
| 7 | "io" |
| 8 | "log/slog" |
| 9 | "os" |
| 10 | "strconv" |
| 11 | "strings" |
| 12 | |
| 13 | "github.com/carlosframework/platform/internal/lease" |
| 14 | "github.com/superfly/ltx" |
| 15 | ) |
| 16 | |
| 17 | // SealedObject is one pinned object version of a generation build's |
| 18 | // source: an LTX file named by its full key, the exact version id the seal |
| 19 | // (or a genselect plan, or a current listing) pinned, and its size. Task 5's |
| 20 | // Seal lists the staging lane's replica/ objects in this shape (plan:688); |
| 21 | // region HA's relocation feeds the same shape from its own pins (L16). |
| 22 | type SealedObject struct { |
| 23 | Key string `json:"key"` |
| 24 | VersionID string `json:"version_id"` |
| 25 | Size int64 `json:"size"` |
| 26 | } |
| 27 | |
| 28 | // ErrSealedReadOnly is every write a SealedClient refuses: the pinned set |
| 29 | // is immutable after the flip, and the build never deletes (§7.6). |
| 30 | var ErrSealedReadOnly = errors.New("moves: the sealed replica is read-only") |
| 31 | |
| 32 | // SealedClient is a litestream.ReplicaClient over exactly one pinned set of |
| 33 | // object versions. Litestream's planner and restore read through it and |
| 34 | // never see a version the seal did not name, whether a newer write to a |
| 35 | // sealed key or an unsealed sibling under the same prefix. A key's position |
| 36 | // (level, min TXID, max TXID) is its last two path elements, |
| 37 | // `<level>/<min>-<max>.ltx`, so the client names no lane or generation. |
| 38 | type SealedClient struct { |
| 39 | store lease.VersionedStore |
| 40 | bucket string |
| 41 | byPos map[sealedPos]SealedObject |
| 42 | infos []ltx.FileInfo |
| 43 | logger *slog.Logger |
| 44 | } |
| 45 | |
| 46 | type sealedPos struct { |
| 47 | level int |
| 48 | min, max ltx.TXID |
| 49 | } |
| 50 | |
| 51 | var _ interface { |
| 52 | Type() string |
| 53 | Init(ctx context.Context) error |
| 54 | LTXFiles(ctx context.Context, level int, seek ltx.TXID, useMetadata bool) (ltx.FileIterator, error) |
| 55 | OpenLTXFile(ctx context.Context, level int, minTXID, maxTXID ltx.TXID, offset, size int64) (io.ReadCloser, error) |
| 56 | WriteLTXFile(ctx context.Context, level int, minTXID, maxTXID ltx.TXID, r io.Reader) (*ltx.FileInfo, error) |
| 57 | DeleteLTXFiles(ctx context.Context, a []*ltx.FileInfo) error |
| 58 | DeleteAll(ctx context.Context) error |
| 59 | SetLogger(logger *slog.Logger) |
| 60 | } = (*SealedClient)(nil) |
| 61 | |
| 62 | // NewSealedClient pins source. It refuses, before any read, an object with |
| 63 | // no usable version id (G27: "" is no version and "null" is what a |
| 64 | // versioning-suspended bucket answers, so neither pins anything), a key |
| 65 | // that is not an LTX file under a level directory, a size below an LTX |
| 66 | // header (litestream's restore refuses such a file, and a size of zero |
| 67 | // would make its premature-EOF detection blind), and two objects at one |
| 68 | // position, which would make the plan ambiguous. |
| 69 | func NewSealedClient(store lease.VersionedStore, bucket string, source []SealedObject) (*SealedClient, error) { |
| 70 | if store == nil || bucket == "" { |
| 71 | return nil, errors.New("moves: sealed client needs a store and a bucket") |
| 72 | } |
| 73 | c := &SealedClient{store: store, bucket: bucket, byPos: map[sealedPos]SealedObject{}, logger: slog.Default()} |
| 74 | for _, o := range source { |
| 75 | if !lease.UsableVersionID(o.VersionID) { |
| 76 | return nil, fmt.Errorf("moves: sealed object %s has no usable version id %q", o.Key, o.VersionID) |
| 77 | } |
| 78 | pos, err := sealedPosition(o.Key) |
| 79 | if err != nil { |
| 80 | return nil, err |
| 81 | } |
| 82 | if o.Size < ltx.HeaderSize { |
| 83 | return nil, fmt.Errorf("moves: sealed object %s has size %d, below an LTX header", o.Key, o.Size) |
| 84 | } |
| 85 | if prev, dup := c.byPos[pos]; dup { |
| 86 | return nil, fmt.Errorf("moves: sealed objects %s and %s share one position", prev.Key, o.Key) |
| 87 | } |
| 88 | c.byPos[pos] = o |
| 89 | c.infos = append(c.infos, ltx.FileInfo{Level: pos.level, MinTXID: pos.min, MaxTXID: pos.max, Size: o.Size}) |
| 90 | } |
| 91 | return c, nil |
| 92 | } |
| 93 | |
| 94 | // sealedPosition reads `<level>/<min>-<max>.ltx` off the end of key, with |
| 95 | // the level directory's four lowercase hex digits and the canonical file |
| 96 | // name, the same shape ReplicaSource's keep admits. |
| 97 | func sealedPosition(key string) (sealedPos, error) { |
| 98 | parts := strings.Split(key, "/") |
| 99 | if len(parts) < 2 { |
| 100 | return sealedPos{}, fmt.Errorf("moves: sealed object %s is not <level>/<min>-<max>.ltx", key) |
| 101 | } |
| 102 | dir, name := parts[len(parts)-2], parts[len(parts)-1] |
| 103 | level, err := strconv.ParseUint(dir, 16, 16) |
| 104 | if err != nil || len(dir) != 4 || fmt.Sprintf("%04x", level) != dir { |
| 105 | return sealedPos{}, fmt.Errorf("moves: sealed object %s has no level directory", key) |
| 106 | } |
| 107 | min, max, err := ltx.ParseFilename(name) |
| 108 | if err != nil || min == 0 || min > max || ltx.FormatFilename(min, max) != name { |
| 109 | return sealedPos{}, fmt.Errorf("moves: sealed object %s is not an LTX file name", key) |
| 110 | } |
| 111 | return sealedPos{level: int(level), min: min, max: max}, nil |
| 112 | } |
| 113 | |
| 114 | // Type names the client in litestream's logs. |
| 115 | func (c *SealedClient) Type() string { return "sealed" } |
| 116 | |
| 117 | // Init has nothing to open: the store is already bound. |
| 118 | func (c *SealedClient) Init(ctx context.Context) error { return nil } |
| 119 | |
| 120 | // SetLogger stores the logger litestream hands over. |
| 121 | func (c *SealedClient) SetLogger(logger *slog.Logger) { |
| 122 | if logger != nil { |
| 123 | c.logger = logger |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | // LTXFiles lists the pinned files at level from seek on, in TXID order. |
| 128 | // useMetadata is ignored: a pinned set has no timestamps to fetch, and the |
| 129 | // build restores by TXID, never by time. |
| 130 | func (c *SealedClient) LTXFiles(ctx context.Context, level int, seek ltx.TXID, useMetadata bool) (ltx.FileIterator, error) { |
| 131 | var out []*ltx.FileInfo |
| 132 | for i := range c.infos { |
| 133 | info := c.infos[i] |
| 134 | if info.Level != level || info.MinTXID < seek { |
| 135 | continue |
| 136 | } |
| 137 | out = append(out, &info) // a copy: the iterator sorts in place |
| 138 | } |
| 139 | return ltx.NewFileInfoSliceIterator(out), nil |
| 140 | } |
| 141 | |
| 142 | // OpenLTXFile streams exactly the pinned version of the file at the |
| 143 | // position, or os.ErrNotExist when the seal names none. offset and size |
| 144 | // follow litestream's convention (size 0 reads to the end) and go through |
| 145 | // the store's VersionRangeOpener when it has one, otherwise the whole |
| 146 | // version is opened and the range is cut locally. |
| 147 | func (c *SealedClient) OpenLTXFile(ctx context.Context, level int, minTXID, maxTXID ltx.TXID, offset, size int64) (io.ReadCloser, error) { |
| 148 | o, ok := c.byPos[sealedPos{level: level, min: minTXID, max: maxTXID}] |
| 149 | if !ok { |
| 150 | return nil, fmt.Errorf("moves: no sealed object at level %d %s: %w", level, ltx.FormatFilename(minTXID, maxTXID), os.ErrNotExist) |
| 151 | } |
| 152 | if offset < 0 || size < 0 { |
| 153 | return nil, fmt.Errorf("moves: invalid range %d+%d for %s", offset, size, o.Key) |
| 154 | } |
| 155 | if offset == 0 && size == 0 { |
| 156 | return c.store.OpenVersion(ctx, c.bucket, o.Key, o.VersionID) |
| 157 | } |
| 158 | if ranged, ok := c.store.(lease.VersionRangeOpener); ok { |
| 159 | length := int64(-1) |
| 160 | if size > 0 { |
| 161 | length = size |
| 162 | } |
| 163 | return ranged.OpenVersionRange(ctx, c.bucket, o.Key, o.VersionID, offset, length) |
| 164 | } |
| 165 | rc, err := c.store.OpenVersion(ctx, c.bucket, o.Key, o.VersionID) |
| 166 | if err != nil { |
| 167 | return nil, err |
| 168 | } |
| 169 | if offset > 0 { |
| 170 | if _, err := io.CopyN(io.Discard, rc, offset); err != nil { |
| 171 | rc.Close() |
| 172 | return nil, fmt.Errorf("moves: skip %d bytes of %s: %w", offset, o.Key, err) |
| 173 | } |
| 174 | } |
| 175 | if size > 0 { |
| 176 | return struct { |
| 177 | io.Reader |
| 178 | io.Closer |
| 179 | }{io.LimitReader(rc, size), rc}, nil |
| 180 | } |
| 181 | return rc, nil |
| 182 | } |
| 183 | |
| 184 | // WriteLTXFile is refused: the pinned set is immutable. |
| 185 | func (c *SealedClient) WriteLTXFile(ctx context.Context, level int, minTXID, maxTXID ltx.TXID, r io.Reader) (*ltx.FileInfo, error) { |
| 186 | return nil, ErrSealedReadOnly |
| 187 | } |
| 188 | |
| 189 | // DeleteLTXFiles is refused: the build never deletes. |
| 190 | func (c *SealedClient) DeleteLTXFiles(ctx context.Context, a []*ltx.FileInfo) error { |
| 191 | return ErrSealedReadOnly |
| 192 | } |
| 193 | |
| 194 | // DeleteAll is refused: the build never deletes. |
| 195 | func (c *SealedClient) DeleteAll(ctx context.Context) error { return ErrSealedReadOnly } |
| 196 | |
amadan