How to capture http messages from Request Node library with Fiddler

Question

Regular client initiated requests to the node server are captured fine in Fiddler. However, requests sent from node to a web service are not captured. It did not help to pass in

Answer 1

I've been wanting the same... an equivalent of the Network tab in chrome DevTools, only for Nodejs. Unfortunately, it doesn't appear as though one exists. I don't have Fiddler on macos, so this is how I went about stubbing the require('http') methods to log and pass though. Leaving this here in case I need it again or someone else finds it helpful. You can turn it on by attaching a debugger and require('filename')() the file containing this script.

module.exports = () => {
    const http = require('http');
    http._request = http.request;

    global.DO_LOG_AJAX = true;
    const log = str => {
        if (global.DO_LOG_AJAX) {
            console.debug(str);
        }
    };

    const flushLog = (requestLines, responseLines) => {
        if (global.DO_LOG_AJAX) {
            log([
                '----------------Begin Request-----------------------------------',
                ...requestLines,
                '----------------End Request / Begin Response--------------------',
                ...responseLines,
                '----------------End Reponse-------------------------------------',
            ].join('\n'));
        }
    };

    let write;
    let end;
    http.request = (...requestParams) => {
        const req = http._request(...requestParams);
        const { method, path, headers, host, port } = requestParams[0];
        const requestLogLines = [];
        requestLogLines.push(`${method} ${path}`);
        requestLogLines.push(`Host: ${host}:${port}`);
        for (const header of Object.keys(headers)) {
            requestLogLines.push(`${header}: ${headers[header]}`);
        }
        write = write || req.write;
        end = end || req.end;

        req.on('error', err => {
            log({ err });
        });

        req._write = write;
        req._end = end;
        const requestBody = [];
        req.write = (...writeParams) => {
            requestBody.push(writeParams[0].toString());
            return req._write(...writeParams);
        };
        req.end = (...endParams) => {
            if (endParams[0]) {
                requestBody.push(endParams[0].toString());
            }
            requestLogLines.push('');
            requestLogLines.push(requestBody.join(''));
            return req._end(...endParams);
        };

        const responseLogLines = [];
        req.once('response', response => {
            const responseBody = [];
            responseLogLines.push(`${response.statusCode} ${response.statusMessage}`);
            for (const header of Object.keys(response.headers)) {
                responseLogLines.push(`${header}: ${response.headers[header]}`);
            }
            const onData = chunk => {
                responseBody.push(chunk.toString());
            };
            const onClose = err => {
                responseLogLines.push('');
                responseLogLines.push(responseBody.join(''));
                responseLogLines.push('');
                responseLogLines.push(`--- ERROR --- ${err.toString()}`);
                flushLog(requestLogLines, responseLogLines);
                req.removeListener('data', onData);
            };
            const onEnd = () => {
                responseLogLines.push('');
                responseLogLines.push(responseBody.join(''));
                flushLog(requestLogLines, responseLogLines);
                req.removeListener('data', onData);
            };
            response.on('data', onData);
            response.once('close', onClose);
            response.once('end', onEnd);
        });

        return req;
    };
};