oailogger.js

// npm i express axios && node ./oailogger.js
const express = require('express');
const axios = require('axios');
const bodyParser = require('body-parser');
const stream = require('stream');
const { promisify } = require('util');
const fs = require('fs');
const logStream = fs.createWriteStream('logs.jsonl', { flags: 'a' });

const app = express();
const OPENAI_API_URL = 'https://api.openai.com';
const pipeline = promisify(stream.pipeline);

app.use(bodyParser.raw({ type: '*/\*' }));

app.all('*', async (req, res) => {
  const path = req.originalUrl;
  const url = `${OPENAI_API_URL}${path}`;
  const headers = { ...req.headers, 'host': new URL(OPENAI_API_URL).host };
  const isStream = JSON.parse(req.body.toString()).stream;

  try {
    const response = await axios({
      method: req.method,
      url: url,
      headers: headers,
      data: req.method === 'POST' ? req.body : undefined,
      responseType: isStream ? 'stream' : 'json'
    });

    if (req.method === 'POST') {
      if (isStream) {
        const responseChunks = [];
        response.data.on('data', (chunk) => {
          responseChunks.push(chunk);
        });

        await pipeline(response.data, res);

        // Process and log the complete response
        const completeResponse = Buffer.concat(responseChunks).toString('utf-8');
        const parsedResponse = completeResponse.split('\n')
          .map(line => {
            if (line.startsWith('data: ')) {
              try {
                return JSON.parse(line.substring('data: '.length));
              } catch (error) {
                return null; // Ignore lines that are not valid JSON
              }
            }
            return null;
          })
          .filter(chunk => chunk !== null)
          .map(chunk => chunk.choices.map(choice => choice.delta?.content).join(''))
          .join('');

        logStream.write(JSON.stringify({
          request: JSON.parse(req.body.toString()),
          response: parsedResponse
        }));
        logStream.write("\n");
      } else {
        // Process and log the complete response
        const completeResponse = response.data.choices[0].message.content;
        logStream.write(JSON.stringify({
          request: JSON.parse(req.body.toString()),
          response: completeResponse
        }));
        logStream.write("\n");

        res.json(response.data);
      }
    } else {
      // For non-POST requests, simply pipe the response or send JSON
      if (isStream) {
        await pipeline(response.data, res);
      } else {
        res.json(response.data);
      }
    }
  } catch (error) {
    console.error(`Error proxying request: ${error}`);
    if (!res.headersSent) {
      res.status(500).send('Internal Server Error');
    }
  }
});

const PORT = process.env.PORT || 5001;
app.listen(PORT, () => console.log(`Proxy server running on port ${PORT}`));

you can test like this

git clone https://github.com/mckaywrigley/chatbot-ui
cd chatbot-ui
echo "DEFAULT_MODEL=gpt-3.5-turbo" >> .env.local
echo "NEXT_PUBLIC_DEFAULT_SYSTEM_PROMPT=You are a helpful AI assistant" >> .env.local
echo "OPENAI_API_KEY=your_key" >> .env.local
echo "OPENAI_API_HOST=http://localhost:5000" >> .env.local
npm i
npm run dev