nai-degen
88 lines
3.0 KiB
TypeScript
88 lines
3.0 KiB
TypeScript
import { pipeline } from "stream";
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import { promisify } from "util";
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import {
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buildFakeSse,
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copySseResponseHeaders,
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initializeSseStream
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} from "../../../shared/streaming";
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import { decodeResponseBody, RawResponseBodyHandler } from ".";
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import { SSEStreamAdapter } from "./streaming/sse-stream-adapter";
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import { SSEMessageTransformer } from "./streaming/sse-message-transformer";
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import { EventAggregator } from "./streaming/event-aggregator";
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const pipelineAsync = promisify(pipeline);
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/**
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* Consume the SSE stream and forward events to the client. Once the stream is
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* stream is closed, resolve with the full response body so that subsequent
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* middleware can work with it.
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*
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* Typically we would only need of the raw response handlers to execute, but
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* in the event a streamed request results in a non-200 response, we need to
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* fall back to the non-streaming response handler so that the error handler
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* can inspect the error response.
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*/
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export const handleStreamedResponse: RawResponseBodyHandler = async (
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proxyRes,
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req,
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res
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) => {
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const { hash } = req.key!;
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if (!req.isStreaming) {
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throw new Error("handleStreamedResponse called for non-streaming request.");
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}
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if (proxyRes.statusCode! > 201) {
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req.isStreaming = false; // Forces non-streaming response handler to execute
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req.log.warn(
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{ statusCode: proxyRes.statusCode, key: hash },
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`Streaming request returned error status code. Falling back to non-streaming response handler.`
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);
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return decodeResponseBody(proxyRes, req, res);
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}
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req.log.debug(
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{ headers: proxyRes.headers, key: hash },
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`Starting to proxy SSE stream.`
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);
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// Users waiting in the queue already have a SSE connection open for the
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// heartbeat, so we can't always send the stream headers.
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if (!res.headersSent) {
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copySseResponseHeaders(proxyRes, res);
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initializeSseStream(res);
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}
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const prefersNativeEvents = req.inboundApi === req.outboundApi;
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const contentType = proxyRes.headers["content-type"];
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const adapter = new SSEStreamAdapter({ contentType });
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const aggregator = new EventAggregator({ format: req.outboundApi });
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const transformer = new SSEMessageTransformer({
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inputFormat: req.outboundApi, // outbound from the request's perspective
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inputApiVersion: String(req.headers["anthropic-version"]),
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logger: req.log,
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requestId: String(req.id),
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requestedModel: req.body.model,
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})
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.on("originalMessage", (msg: string) => {
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if (prefersNativeEvents) res.write(msg);
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})
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.on("data", (msg) => {
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if (!prefersNativeEvents) res.write(`data: ${JSON.stringify(msg)}\n\n`);
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aggregator.addEvent(msg);
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});
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try {
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await pipelineAsync(proxyRes, adapter, transformer);
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req.log.debug({ key: hash }, `Finished proxying SSE stream.`);
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res.end();
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return aggregator.getFinalResponse();
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} catch (err) {
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const errorEvent = buildFakeSse("stream-error", err.message, req);
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res.write(`${errorEvent}data: [DONE]\n\n`);
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res.end();
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throw err;
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}
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};
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