add caching

[trickydisco78]

Anyone managed to add caching to the onProxyReq option?

I've added a memory caching function to onProxyReq

proxy middleware configuration

var cache = duration => {
  return (proxyReq, req, res) => {
    let key = '__express__' + proxyReq.path || proxyReq.url;
    //console.log(proxyReq);
    console.log(key);
    let cachedBody = mcache.get(key);
    console.log(cachedBody);
    if (cachedBody) {
      console.log('use cache');
      res.send(cachedBody);
      return;
    } else {
      console.log('set cache');
      //console.log(body);
      console.log(res.send);
      res.sendResponse = res.send;
      res.send = body => {
        console.log(body);
        mcache.put(key, body, duration * 5000);
        console.log('set cache');
        res.sendResponse(body);
        return;
      };
    }
  };
};

onProxyReq: cache(10),

It looks like it's not grabbing the body information or getting to set the cache at

mcache.put(key, body, duration * 5000);

body comes up as null as wel

Any ideas?

[trickydisco78]

I've managed to do this using the apicache npm module

[liorbd]

@trickydisco78 can you share your solution?

[trickydisco78]

Yep: here: https://glitch.com/~flint-garage

But i've now found this which is much better : https://github.com/daniloc/airtable-api-proxy

[sebtoombs]

I'm aware this is closed, but If anybody finds this in 2019 via Google as I did, I came up with a solution I think works well. I'm using express and http-proxy-middleware. Essentially the cache middleware just runs before the proxy middleware. The only tricky part is getting the response from the proxy. Here's my solution:

server.use(
        '/proxypath',
        cacheMiddleware(10),
        proxyMiddleware
);

//cacheMiddleware
var mcache = require('memory-cache');

var cacheMiddleware = (duration) => {
    return (req, res, next) => {
        if(req.method !== "GET") return next();

        let key = '__proxy_cache__' + req.originalUrl || req.url

        let cachedBody = mcache.get(key)
        if (cachedBody) {
            res.send(cachedBody)
        } else {

            var _end = res.end;
            var _write = res.write;
            var buffer = new Buffer.alloc(0);
            // Rewrite response method and get the content.
            res.write = function (data) {
                buffer = Buffer.concat([buffer, data]);
            };
            res.end = function() {
                var body = buffer.toString();
                mcache.put(key, body, duration * 1000);
                _write.call(res, body);
                _end.call(res);
            };
            next()
        }
    }
}

//ProxyMiddleware eg
var proxyMiddleware = proxy({
    target: 'http://localhost:3000/'
});

This is simply using the proxyMiddleware as per the examples, but running a cache middleware first. The cache middleware (only for GET requests) checks if the path is in cache, and if so returns the body from cache and ends the route handler. If it's not in cache it passes on to the proxy handler, but first modifies the res.end (there are other ways to do this, but this seems to be the most reliable?) function to grab a copy of the response body and store in cache.

[dptoot]

@sebtoombs I like your solution but seem to be getting an incorrect header check error... any ideas or experience? google search is not helping me :(

It seems to be something about the Buffer but my research is saying the Buffer concat is the answer but you already have that in place...

[animhotep]

res.send is not a function

this function is working for me now

function cache(req, res, next) {
        if(req.method !== 'GET') return next();

        let key = '__proxy_cache1__' + req.originalUrl || req.url;

        let cachedBody = mcache.get(key);
        if (cachedBody) {
            console.log('from cache =>> ', req.originalUrl);
            res.writeHead(200, {'Content-Type': 'application/json'});
            res.send(cachedBody);
            res.end();
            next();
        } else {
            console.log('cached', req.originalUrl);
            var _end = res.end;
            var _write = res.write;
            var buffer = new Buffer.alloc(0);
            // Rewrite response method and get the content.
            res.write = function (data) {
                buffer = Buffer.concat([buffer, data]);
            };
            res.end = function () {
                var body = buffer.toString();
                mcache.put(key, body);
                _write.call(res, body);
                _end.call(res);
            };
            next();
        }
    }