How to log request and response urls?

I would like to log each request no matter what status code the target server responded. I’m trying to achieve the following format:

// Format:
// -->  [METHOD] [PATH_REQUESTED_FROM_PROXY] -> [URL_REQUESTED_FROM_TARGET]
// Example:
// -->  GET /v1/users/123 -> https://my-app.herokuapp.com/api/v1/users/123

My proxy options are:

var proxyOpts = {
    target: 'https://my-app.herokuapp.com/',
    pathRewrite: {
        '^/v1' : '/api/v1'
    },
    onProxyReq: function onProxyReq(proxyReq, req, res) {
        // Log outbound request to remote target
        console.log('-->  ', req.method, req.path, '->', proxyReq.baseUrl + proxyReq.path);
    },
    onError: function onError(err, req, res) {
        console.error(err);
        res.status(500);
        res.json({error: 'Error when connecting to remote server.'});
    },
    logLevel: 'debug',
    changeOrigin: true,
    secure: true
};

Which outputs:

-->   GET /api/v1/users/123 -> undefined/api/v1/users/123

Problems:

• req.path is already converted to the new format with pathRewrite, I would want to log the url which client actually requested from this proxy server
• proxyReq.baseUrl is not defined, I’m not sure what I should use to get the host part of the request.

[chimurai]

Think with onProxyRes you should be able to get the logging you want:

  onProxyRes: (proxyRes, req, res) => {
    // log original request and proxied request info
    const exchange = `[${req.method}] [${proxyRes.statusCode}] ${req.path} -> ${proxyRes.req.protocol}//${proxyRes.req.host}${proxyRes.req.path}`;
    console.log(exchange); // [GET] [200] / -> http://www.example.com
  },

[chimurai]

I think will be nice to encode the proxy behavior in the log statements too; Different arrows indicate what happend:

• -> default.
• ~> pathRewrite applied.
• => proxyTable applied.
• ≈> both pathRewrite and proxyTable applied.

So in your use-case; the original url will get logged, its target URI and the pathRewrite arrow.

[HPM] GET /v1/users/123 ~> https://my-app.herokuapp.com/api/v1/users/123

Let me know what you think.