fix(combos): fail over zero-output stream failures #2433
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,171 @@ | ||
| import type { ResponsesTerminalStatus } from "../../bridge"; | ||
| import type { RequestLogContext } from "../request-log"; | ||
| import { createSseInspector } from "../relay"; | ||
| import { MAX_CLIENT_SSE_FRAME_BYTES } from "../sse-frame-buffer"; | ||
|
|
||
| const COMBO_STREAM_PREFLIGHT_MAX_BYTES = MAX_CLIENT_SSE_FRAME_BYTES; | ||
|
|
||
| const PRE_OUTPUT_CONTROL_EVENTS = new Set([ | ||
| "response.created", | ||
| "response.in_progress", | ||
| "response.queued", | ||
| "response.heartbeat", | ||
| ]); | ||
|
|
||
| const TERMINAL_EVENTS = new Set([ | ||
| "response.completed", | ||
| "response.failed", | ||
| "response.incomplete", | ||
| ]); | ||
|
|
||
| /** | ||
| * Decide when replaying the request on another combo target would risk duplicating | ||
| * client-visible output or a tool-side effect. Unknown event types commit the child | ||
| * conservatively; only the small Responses lifecycle preamble remains replayable. | ||
| */ | ||
| export function comboStreamPayloadCommitsOutput(payload: unknown): boolean { | ||
| if (!payload || typeof payload !== "object" || Array.isArray(payload)) return true; | ||
| const type = (payload as { type?: unknown }).type; | ||
| if (typeof type !== "string") return true; | ||
| return !PRE_OUTPUT_CONTROL_EVENTS.has(type) && !TERMINAL_EVENTS.has(type); | ||
| } | ||
|
|
||
| function replayBufferedResponse( | ||
| response: Response, | ||
| reader: ReadableStreamDefaultReader<Uint8Array>, | ||
| buffered: Uint8Array[], | ||
| ): Response { | ||
| let index = 0; | ||
| const body = new ReadableStream<Uint8Array>({ | ||
| async pull(controller) { | ||
| if (index < buffered.length) { | ||
| controller.enqueue(buffered[index++]!); | ||
| return; | ||
| } | ||
| try { | ||
| const next = await reader.read(); | ||
| if (next.done) controller.close(); | ||
| else controller.enqueue(next.value); | ||
| } catch (error) { | ||
| try { controller.error(error); } catch { /* consumer already closed */ } | ||
| } | ||
| }, | ||
| cancel(reason) { | ||
| reader.cancel(reason).catch(() => undefined); | ||
| }, | ||
| }); | ||
| return new Response(body, { | ||
| status: response.status, | ||
| statusText: response.statusText, | ||
| headers: response.headers, | ||
| }); | ||
| } | ||
|
|
||
| function failedTerminalResponse( | ||
| response: Response, | ||
| terminalPayload: Record<string, unknown>, | ||
| logCtx: RequestLogContext, | ||
| ): Response { | ||
| const nested = terminalPayload.response; | ||
| const terminalResponse = nested && typeof nested === "object" && !Array.isArray(nested) | ||
| ? nested as Record<string, unknown> | ||
| : {}; | ||
| const nestedError = terminalResponse.error; | ||
| const error = nestedError && typeof nestedError === "object" && !Array.isArray(nestedError) | ||
| ? nestedError as Record<string, unknown> | ||
| : { | ||
| type: "upstream_error", | ||
| code: "upstream_server_error", | ||
| message: logCtx.upstreamError ?? "Provider stream failed before producing output", | ||
| }; | ||
| const headers = new Headers(response.headers); | ||
| headers.set("content-type", "application/json"); | ||
| headers.delete("content-length"); | ||
| headers.delete("content-encoding"); | ||
| const usage = terminalResponse.usage; | ||
| return new Response(JSON.stringify({ | ||
| error, | ||
| // The combo classifier needs only the error and optional usage. Do not carry | ||
| // response ids, provider metadata, or future terminal fields into the client | ||
| // error envelope merely because they shared the terminal snapshot. | ||
| response: { | ||
| error, | ||
| ...(usage && typeof usage === "object" && !Array.isArray(usage) ? { usage } : {}), | ||
| }, | ||
| }), { | ||
| status: logCtx.terminalHttpStatus ?? 502, | ||
| headers, | ||
| }); | ||
| } | ||
|
|
||
| export type ComboStreamPreflightResult = | ||
| | { kind: "accepted"; response: Response } | ||
| | { kind: "failed"; response: Response }; | ||
|
|
||
| /** | ||
| * Buffer a combo child's downstream SSE only until the request becomes unsafe to | ||
| * replay or reaches a terminal. This owns exactly one body reader. The aggregate | ||
| * buffer is capped; hitting the cap commits the current target instead of growing | ||
| * memory or guessing that replay is safe. | ||
| */ | ||
| export async function preflightComboStreamResponse( | ||
| response: Response, | ||
| logCtx: RequestLogContext, | ||
| ): Promise<ComboStreamPreflightResult> { | ||
| const contentType = response.headers.get("content-type")?.toLowerCase() ?? ""; | ||
| if (!response.ok || !response.body || !contentType.includes("text/event-stream")) { | ||
| return { kind: "accepted", response }; | ||
| } | ||
|
|
||
| const reader = response.body.getReader(); | ||
| const buffered: Uint8Array[] = []; | ||
| let bufferedBytes = 0; | ||
| let outputCommitted = false; | ||
| let terminalStatus: ResponsesTerminalStatus | undefined; | ||
| let failedPayload: Record<string, unknown> | undefined; | ||
| const inspector = createSseInspector({ | ||
| logCtx, | ||
| onParsedPayload: payload => { | ||
| if (comboStreamPayloadCommitsOutput(payload)) outputCommitted = true; | ||
| if (!payload || typeof payload !== "object" || Array.isArray(payload)) return; | ||
| if ((payload as { type?: unknown }).type === "response.failed") { | ||
| failedPayload = payload as Record<string, unknown>; | ||
| } | ||
| }, | ||
| onTerminal: status => { terminalStatus = status; }, | ||
| }); | ||
|
|
||
| try { | ||
| for (;;) { | ||
| const next = await reader.read(); | ||
| if (next.done) { | ||
| inspector.finish(); | ||
| } else { | ||
| if (bufferedBytes + next.value.byteLength > COMBO_STREAM_PREFLIGHT_MAX_BYTES) { | ||
| // Keep the cap about memory the preflight allocates. The upstream chunk already exists; | ||
| // copying it before committing would transiently exceed the boundary for no | ||
| // replay benefit. Preserve it unsliced behind the already-bounded prefix. | ||
| return { | ||
| kind: "accepted", | ||
| response: replayBufferedResponse(response, reader, [...buffered, next.value]), | ||
| }; | ||
| } | ||
| const retained = next.value.slice(); | ||
| buffered.push(retained); | ||
| bufferedBytes += retained.byteLength; | ||
| inspector.feed(retained); | ||
| } | ||
|
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||
| if (terminalStatus === "failed" && !outputCommitted && failedPayload) { | ||
| await reader.cancel("retrying zero-output combo stream failure").catch(() => undefined); | ||
| return { kind: "failed", response: failedTerminalResponse(response, failedPayload, logCtx) }; | ||
| } | ||
| if (next.done || terminalStatus !== undefined || outputCommitted | ||
| || bufferedBytes >= COMBO_STREAM_PREFLIGHT_MAX_BYTES) { | ||
| return { kind: "accepted", response: replayBufferedResponse(response, reader, buffered) }; | ||
|
coderabbitai[bot] marked this conversation as resolved.
|
||
| } | ||
| } | ||
| } finally { | ||
| inspector.dispose(); | ||
| } | ||
| } | ||
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