| 1 | package dbdoor |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "encoding/json" |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "io" |
| 9 | "log/slog" |
| 10 | "net/http" |
| 11 | "os" |
| 12 | "strconv" |
| 13 | "strings" |
| 14 | "time" |
| 15 | |
| 16 | "github.com/benbjohnson/litestream" |
| 17 | "github.com/superfly/ltx" |
| 18 | ) |
| 19 | |
| 20 | // Doer sends one GET to the door for one instance. tail is relative to the |
| 21 | // instance's door root (ListTail or GetTail); the caller owns the console |
| 22 | // URL, the bearer and the account segment, which is why the client never |
| 23 | // sees them. The caller's response body is the client's to close. |
| 24 | type Doer func(ctx context.Context, tail string, header http.Header) (*http.Response, error) |
| 25 | |
| 26 | // Client is the CLI's litestream.ReplicaClient over the db door (spec |
| 27 | // 2026-09-02 §6, "The read-only replica client"), the way internal/fleetapi |
| 28 | // implements release.Store over the edge store door: the member has no AWS |
| 29 | // credentials, by design. |
| 30 | // |
| 31 | // It supplies the five methods a restore needs (Type, Init, LTXFiles, |
| 32 | // OpenLTXFile, SetLogger). The three that mutate a replica return |
| 33 | // errReadOnly and have no other body. It must never implement |
| 34 | // litestream.ReplicaClientV3, or Restore would take the v0.3 path. |
| 35 | type Client struct { |
| 36 | handles dbHandleState |
| 37 | do Doer |
| 38 | logger *slog.Logger |
| 39 | } |
| 40 | |
| 41 | // NewClient returns a read-only replica client that reads through do. |
| 42 | func NewClient(do Doer) *Client { |
| 43 | return &Client{do: do, logger: slog.Default()} |
| 44 | } |
| 45 | |
| 46 | // errReadOnly is not a guard that can be switched off: these three methods |
| 47 | // have no other body. The two-replicators hazard internal/caps and |
| 48 | // internal/lease both warn about is unreachable from this client by |
| 49 | // construction, and a future edit that wanted to reach it would have to add |
| 50 | // the capability first. |
| 51 | var errReadOnly = errors.New("dbdoor: this client is read-only; it restores replicas and never writes them") |
| 52 | |
| 53 | // DoorError is a refusal from the door, carrying the console's own sentence |
| 54 | // (its {"error"} body) so the CLI can show it as written. |
| 55 | type DoorError struct { |
| 56 | Status int |
| 57 | Message string |
| 58 | // RetryAfter is the door's Retry-After, in whole seconds, when it sent |
| 59 | // one (a 429 from a full stream bound does); zero otherwise. |
| 60 | RetryAfter time.Duration |
| 61 | // Forward is the list door's forward marker on a 409 (db region |
| 62 | // forward spec §5.5): the instance is readable through the forwarded |
| 63 | // read in Forward.Region. nil for every other refusal. |
| 64 | Forward *Forward |
| 65 | } |
| 66 | |
| 67 | func (e *DoorError) Error() string { |
| 68 | if e.Message == "" { |
| 69 | return fmt.Sprintf("the console answered %d", e.Status) |
| 70 | } |
| 71 | return e.Message |
| 72 | } |
| 73 | |
| 74 | func (c *Client) Type() string { return "carlos-db" } |
| 75 | |
| 76 | // Init is a no-op: the transport needs no setup, and litestream requires |
| 77 | // it to be idempotent. |
| 78 | func (c *Client) Init(context.Context) error { return nil } |
| 79 | |
| 80 | func (c *Client) SetLogger(l *slog.Logger) { c.logger = l } |
| 81 | |
| 82 | // LTXFiles lists one level. seek is filtered here (wire specific 3), with |
| 83 | // litestream's own rule: files whose MinTXID is below seek are skipped. |
| 84 | // useMetadata is ignored; nothing in a non-timestamp restore reads |
| 85 | // CreatedAt except debug logs. |
| 86 | func (c *Client) LTXFiles(ctx context.Context, level int, seek ltx.TXID, _ bool) (ltx.FileIterator, error) { |
| 87 | c.handles.listMu.Lock() |
| 88 | defer c.handles.listMu.Unlock() |
| 89 | files, ok := c.planFiles(level) |
| 90 | if !ok { |
| 91 | var err error |
| 92 | files, err = c.listFiles(ctx, level) |
| 93 | if err != nil { |
| 94 | return nil, err |
| 95 | } |
| 96 | } |
| 97 | return fileIterator(files, level, seek), nil |
| 98 | } |
| 99 | |
| 100 | func (c *Client) listFiles(ctx context.Context, level int) ([]LTXFile, error) { |
| 101 | res, err := c.do(ctx, ListTail(level), http.Header{}) |
| 102 | if err != nil { |
| 103 | return nil, err |
| 104 | } |
| 105 | defer res.Body.Close() |
| 106 | if res.StatusCode != http.StatusOK { |
| 107 | return nil, doorError(res) |
| 108 | } |
| 109 | var list ListResponse |
| 110 | if err := json.NewDecoder(io.LimitReader(res.Body, 16<<20)).Decode(&list); err != nil { |
| 111 | return nil, fmt.Errorf("dbdoor: unreadable listing for level %d: %w", level, err) |
| 112 | } |
| 113 | return c.rememberFiles(level, list) |
| 114 | } |
| 115 | |
| 116 | func fileIterator(files []LTXFile, level int, seek ltx.TXID) ltx.FileIterator { |
| 117 | infos := make([]*ltx.FileInfo, 0, len(files)) |
| 118 | for _, f := range files { |
| 119 | if ltx.TXID(f.MinTXID) < seek { |
| 120 | continue |
| 121 | } |
| 122 | infos = append(infos, <x.FileInfo{ |
| 123 | Level: level, MinTXID: ltx.TXID(f.MinTXID), MaxTXID: ltx.TXID(f.MaxTXID), |
| 124 | Size: f.Size, CreatedAt: f.CreatedAt, |
| 125 | }) |
| 126 | } |
| 127 | return ltx.NewFileInfoSliceIterator(infos) |
| 128 | } |
| 129 | |
| 130 | // OpenLTXFile opens one file by coordinate, sending the S3 client's exact |
| 131 | // Range form. A 404 is os.ErrNotExist (wire specific 5): that is what lets |
| 132 | // RestoreTo tell a file that vanished under the plan from a refusal. |
| 133 | func (c *Client) OpenLTXFile(ctx context.Context, level int, minTXID, maxTXID ltx.TXID, offset, size int64) (io.ReadCloser, error) { |
| 134 | h := http.Header{} |
| 135 | handle, err := c.fileHandle(level, uint64(minTXID), uint64(maxTXID)) |
| 136 | if err != nil { |
| 137 | return nil, err |
| 138 | } |
| 139 | if handle != "" { |
| 140 | h.Set(HandleHeader, handle) |
| 141 | } |
| 142 | h.Set("Range", RangeHeader(offset, size)) |
| 143 | res, err := c.do(ctx, GetTail(level, uint64(minTXID), uint64(maxTXID)), h) |
| 144 | if err != nil { |
| 145 | return nil, err |
| 146 | } |
| 147 | switch res.StatusCode { |
| 148 | case http.StatusOK, http.StatusPartialContent: |
| 149 | if handle != "" && res.Header.Get(HandleHeader) != handle { |
| 150 | res.Body.Close() |
| 151 | return nil, errors.New("dbdoor: console did not enforce the pinned handle") |
| 152 | } |
| 153 | return res.Body, nil |
| 154 | case http.StatusNotFound: |
| 155 | res.Body.Close() |
| 156 | return nil, fmt.Errorf("dbdoor: level %d %s: %w", level, Span(uint64(minTXID), uint64(maxTXID)), os.ErrNotExist) |
| 157 | default: |
| 158 | defer res.Body.Close() |
| 159 | return nil, doorError(res) |
| 160 | } |
| 161 | } |
| 162 | |
| 163 | func (c *Client) WriteLTXFile(context.Context, int, ltx.TXID, ltx.TXID, io.Reader) (*ltx.FileInfo, error) { |
| 164 | return nil, errReadOnly |
| 165 | } |
| 166 | |
| 167 | func (c *Client) DeleteLTXFiles(context.Context, []*ltx.FileInfo) error { return errReadOnly } |
| 168 | |
| 169 | func (c *Client) DeleteAll(context.Context) error { return errReadOnly } |
| 170 | |
| 171 | // doorError reads a refusal's {"error"} sentence, and the db region |
| 172 | // forward marker beside it on a 409. A body that is not that |
| 173 | // shape (the stdlib's 404 text, a proxy's page) keeps only the status. |
| 174 | func doorError(res *http.Response) error { |
| 175 | raw, _ := io.ReadAll(io.LimitReader(res.Body, 64<<10)) |
| 176 | var body struct { |
| 177 | Error string `json:"error"` |
| 178 | Forward int `json:"forward"` |
| 179 | Region string `json:"region"` |
| 180 | ForwardOps []string `json:"forward_ops"` |
| 181 | } |
| 182 | e := &DoorError{Status: res.StatusCode} |
| 183 | if json.Unmarshal(raw, &body) == nil { |
| 184 | e.Message = strings.TrimSpace(body.Error) |
| 185 | if res.StatusCode == http.StatusConflict && body.Forward == 1 && forwardRegion.MatchString(body.Region) { |
| 186 | e.Forward = &Forward{Region: body.Region, Ops: body.ForwardOps} |
| 187 | } |
| 188 | } |
| 189 | // Seconds only (the door never sends a date), capped so a hostile or |
| 190 | // broken value cannot park a download for hours. |
| 191 | if secs, err := strconv.Atoi(strings.TrimSpace(res.Header.Get("Retry-After"))); err == nil && secs > 0 { |
| 192 | // Clamp the count before multiplying: a large one would wrap. |
| 193 | e.RetryAfter = time.Duration(min(secs, 60)) * time.Second |
| 194 | } |
| 195 | return e |
| 196 | } |
| 197 | |
| 198 | var _ litestream.ReplicaClient = (*Client)(nil) |
| 199 | |
amadan