response-interceptor.js
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"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.responseInterceptor = void 0;
const zlib = require("zlib");
/**
* Intercept responses from upstream.
* Automatically decompress (deflate, gzip, brotli).
* Give developer the opportunity to modify intercepted Buffer and http.ServerResponse
*
* NOTE: must set options.selfHandleResponse=true (prevent automatic call of res.end())
*/
function responseInterceptor(interceptor) {
return async function proxyRes(proxyRes, req, res) {
const originalProxyRes = proxyRes;
let buffer = Buffer.from('', 'utf8');
// decompress proxy response
const _proxyRes = decompress(proxyRes, proxyRes.headers['content-encoding']);
// concat data stream
_proxyRes.on('data', (chunk) => (buffer = Buffer.concat([buffer, chunk])));
_proxyRes.on('end', async () => {
// copy original headers
copyHeaders(proxyRes, res);
// call interceptor with intercepted response (buffer)
const interceptedBuffer = Buffer.from(await interceptor(buffer, originalProxyRes, req, res));
// set correct content-length (with double byte character support)
res.setHeader('content-length', Buffer.byteLength(interceptedBuffer, 'utf8'));
res.write(interceptedBuffer);
res.end();
});
_proxyRes.on('error', (error) => {
res.end(`Error fetching proxied request: ${error.message}`);
});
};
}
exports.responseInterceptor = responseInterceptor;
/**
* Streaming decompression of proxy response
* source: https://github.com/apache/superset/blob/9773aba522e957ed9423045ca153219638a85d2f/superset-frontend/webpack.proxy-config.js#L116
*/
function decompress(proxyRes, contentEncoding) {
let _proxyRes = proxyRes;
let decompress;
switch (contentEncoding) {
case 'gzip':
decompress = zlib.createGunzip();
break;
case 'br':
decompress = zlib.createBrotliDecompress();
break;
case 'deflate':
decompress = zlib.createInflate();
break;
default:
break;
}
if (decompress) {
_proxyRes.pipe(decompress);
_proxyRes = decompress;
}
return _proxyRes;
}
/**
* Copy original headers
* https://github.com/apache/superset/blob/9773aba522e957ed9423045ca153219638a85d2f/superset-frontend/webpack.proxy-config.js#L78
*/
function copyHeaders(originalResponse, response) {
response.statusCode = originalResponse.statusCode;
response.statusMessage = originalResponse.statusMessage;
if (response.setHeader) {
let keys = Object.keys(originalResponse.headers);
// ignore chunked, brotli, gzip, deflate headers
keys = keys.filter((key) => !['content-encoding', 'transfer-encoding'].includes(key));
keys.forEach((key) => {
let value = originalResponse.headers[key];
if (key === 'set-cookie') {
// remove cookie domain
value = Array.isArray(value) ? value : [value];
value = value.map((x) => x.replace(/Domain=[^;]+?/i, ''));
}
response.setHeader(key, value);
});
}
else {
response.headers = originalResponse.headers;
}
}