Müşkülpesent•2w ago

Windmill SSE response format — emit one item per event?

Hi, I’m trying to use Server-Sent Events (SSE) with streamed responses in a script, but the Windmill SSE endpoint appears to “flush” multiple items into a single event. That doesn’t match the per-item yield format I expect. My main scenario uses the ai-sdk tooling for streaming. Here’s a simplified example:

import { createUIMessageStream, streamText } from "ai";
import { createOpenAI } from "@ai-sdk/openai";
import * as wmill from "windmill-client@1.545.0";

export async function main() {
  return streamMe();
}

async function* streamMe(): AsyncGenerator<any> {
  const prompt = "write me a poen about nature";

  const { api_key } = (await wmill.getResource(
    "f/openai_key"
  )) as { api_key: string };

  const openai = createOpenAI({ apiKey: api_key });

  const result = streamText({
    model: openai("gpt-4o-mini"),
    prompt
  });

  const uiStream = createUIMessageStream({
    execute: ({ writer }) => {
      writer.merge(
        result.toUIMessageStream({
          sendReasoning: true,
          onError: error =>
            error instanceof Error ? error.message : String(error),
        })
      );
    },
  });

  const reader = uiStream.getReader();
  try {
    while (true) {
      const { value, done } = await reader.read();
      if (done) {
        break;
      }
      yield JSON.stringify(value);
    }
  } finally {
    reader.releaseLock();
  }

}

import { createUIMessageStream, streamText } from "ai";
import { createOpenAI } from "@ai-sdk/openai";
import * as wmill from "windmill-client@1.545.0";

export async function main() {
  return streamMe();
}

async function* streamMe(): AsyncGenerator<any> {
  const prompt = "write me a poen about nature";

  const { api_key } = (await wmill.getResource(
    "f/openai_key"
  )) as { api_key: string };

  const openai = createOpenAI({ apiKey: api_key });

  const result = streamText({
    model: openai("gpt-4o-mini"),
    prompt
  });

  const uiStream = createUIMessageStream({
    execute: ({ writer }) => {
      writer.merge(
        result.toUIMessageStream({
          sendReasoning: true,
          onError: error =>
            error instanceof Error ? error.message : String(error),
        })
      );
    },
  });

  const reader = uiStream.getReader();
  try {
    while (true) {
      const { value, done } = await reader.read();
      if (done) {
        break;
      }
      yield JSON.stringify(value);
    }
  } finally {
    reader.releaseLock();
  }

}

A sample response from the Windmill SSE endpoint (attached) looks like this:

data: {"type":"update","new_result_stream":"{json object...}{json object...}{json object...}"}

data: {"type":"update","new_result_stream":"{json object...}{json object...}{json object...}"}

However, I need one JSON object per SSE event because I iterate over each item. The expected output would be:

data: {"type":"update","new_result_stream":"{json object...}"}

data: {"type":"update","new_result_stream":"{json object}"}

data: {"type":"update","new_result_stream":"{json object}"}

data: {"type":"update","new_result_stream":"{json object...}"}

data: {"type":"update","new_result_stream":"{json object}"}

data: {"type":"update","new_result_stream":"{json object}"}

is there a way for formating like that?

windmill_sse_respons...

5 Replies

MüşkülpesentOP•2w ago

By the way, my windmill version is CE v1.558.1

Hugo•2w ago

can't you simply split on line breaks on the client side?

MüşkülpesentOP•2w ago

Hello @Hugo C. , thanks for your response Based on my research, there are off-the-shelf solutions for NDJSON, but I couldn’t find any for concatenated JSON. I’d prefer not to write my own parser for this format because the JSON content is complex and I don’t want to risk misparsing. it feels like a very custom solution. Do you have any recommendations?

Hugo•2w ago

you can yield the stringified object + a line break and then use an off the shelf solution for NDJSON

MüşkülpesentOP•2w ago

What you said makes a lot of sense! I’ll try it thanks 🙂

Windmill SSE response format — emit one item per event?

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