Koa middleware to proxy request to another host and pass response back. Based on express-http-proxy.
$ npm install koa-better-http-proxy --saveproxy(host, options);To proxy URLS to the host 'www.google.com':
var proxy = require('koa-better-http-proxy');
var Koa = require('koa');
var app = new Koa();
app.use(proxy('www.google.com'));If you wish to proxy only specific paths, you can use a router middleware to accomplish this. See Koa routing middlewares.
The port to use for the proxied host.
app.use(proxy('www.google.com', {
port: 443
}));Additional headers to send to the proxied host.
app.use(proxy('www.google.com', {
headers: {
'X-Special-Header': 'true'
}
}));Pass the session along to the proxied request
app.use(proxy('www.google.com', {
preserveReqSession: true
}));Provide a proxyReqPathResolver function if you'd like to operate on the path before issuing the proxy request. Use a Promise for async operations.
app.use(proxy('localhost:12345', {
proxyReqPathResolver: function(ctx) {
return require('url').parse(ctx.url).path;
}
}));Promise form
app.use(proxy('localhost:12345', {
proxyReqPathResolver: function(ctx) {
return new Promise(function (resolve, reject) {
setTimeout(function () { // do asyncness
resolve(fancyResults);
}, 200);
});
}
}));The filter option can be used to limit what requests are proxied. Return true to execute proxy.
For example, if you only want to proxy get request:
app.use(proxy('www.google.com', {
filter: function(ctx) {
return ctx.method === 'GET';
}
}));You can modify the proxy's response before sending it to the client.
The intent is that this be used to modify the proxy response data only.
Note: The other arguments (proxyRes, ctx) are passed by reference, so you can currently exploit this to modify either response's headers, for instance, but this is not a reliable interface. I expect to close this exploit in a future release, while providing an additional hook for mutating the userRes before sending.
If your proxy response is gzipped, this program will automatically unzip it before passing to your function, then zip it back up before piping it to the user response. There is currently no way to short-circuit this behavior.
app.use(proxy('www.google.com', {
userResDecorator: function(proxyRes, proxyResData, ctx) {
data = JSON.parse(proxyResData.toString('utf8'));
data.newProperty = 'exciting data';
return JSON.stringify(data);
}
}));app.use(proxy('httpbin.org', {
userResDecorator: function(proxyRes, proxyResData) {
return new Promise(function(resolve) {
proxyResData.funkyMessage = 'oi io oo ii';
setTimeout(function() {
resolve(proxyResData);
}, 200);
});
}
}));This sets the body size limit (default: 1mb). If the body size is larger than the specified (or default) limit,
a 413 Request Entity Too Large error will be returned. See bytes.js for
a list of supported formats.
app.use(proxy('www.google.com', {
limit: '5mb'
}));You can mutate the request options before sending the proxyRequest. proxyReqOpt represents the options argument passed to the (http|https).request module.
app.use(proxy('www.google.com', {
proxyReqOptDecorator: function(proxyReqOpts, ctx) {
// you can update headers
proxyReqOpts.headers['content-type'] = 'text/html';
// you can change the method
proxyReqOpts.method = 'GET';
// you could change the path
proxyReqOpts.path = 'http://dev/null'
return proxyReqOpts;
}
}));You can use a Promise for async style.
app.use(proxy('www.google.com', {
proxyReqOptDecorator: function(proxyReqOpts, ctx) {
return new Promise(function(resolve, reject) {
proxyReqOpts.headers['content-type'] = 'text/html';
resolve(proxyReqOpts);
})
}
}));You can mutate the body content before sending the proxyRequest.
app.use(proxy('www.google.com', {
proxyReqBodyDecorator: function(bodyContent, ctx) {
return bodyContent.split('').reverse().join('');
}
}));You can use a Promise for async style.
app.use(proxy('www.google.com', {
proxyReqBodyDecorator: function(proxyReq, ctx) {
return new Promise(function(resolve, reject) {
http.get('http://dev/null', function (err, res) {
if (err) { reject(err); }
resolve(res);
});
})
}
}));Normally, your proxy request will be made on the same protocol as the original request. If you'd like to force the proxy request to be https, use this option.
app.use(proxy('www.google.com', {
https: true
}));You can copy the host HTTP header to the proxied express server using the preserveHostHdr option.
app.use(proxy('www.google.com', {
preserveHostHdr: true
}));The parseReqBody option allows you to control parsing the request body.
For example, disabling body parsing is useful for large uploads where it would be inefficient
to hold the data in memory.
This defaults to true in order to preserve legacy behavior.
When false, no action will be taken on the body and accordingly req.body will no longer be set.
Note that setting this to false overrides reqAsBuffer and reqBodyEncoding below.
app.use(proxy('www.google.com', {
parseReqBody: false
}));Note: this is an experimental feature. ymmv
The reqAsBuffer option allows you to ensure the req body is encoded as a Node
Buffer when sending a proxied request. Any value for this is truthy.
This defaults to to false in order to preserve legacy behavior. Note that
the value of reqBodyEnconding is used as the encoding when coercing strings
(and stringified JSON) to Buffer.
Ignored if parseReqBody is set to false.
app.use(proxy('www.google.com', {
reqAsBuffer: true
}));Encoding used to decode request body. Defaults to utf-8.
Use null to preserve as Buffer when proxied request body is a Buffer. (e.g image upload)
Accept any values supported by raw-body.
The same encoding is used in the userResDecorator method.
Ignored if parseReqBody is set to false.
app.use(proxy('httpbin.org', {
reqBodyEncoding: null
}));By default, node does not express a timeout on connections. Use timeout option to impose a specific timeout. Timed-out requests will respond with 504 status code and a X-Timeout-Reason header.
app.use(proxy('httpbin.org', {
timeout: 2000 // in milliseconds, two seconds
}));