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app.js
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app.js
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const express = require('express');
const http = require('http');
const dns = require('dns');
const app = express();
const port = 3000;
const forwardEndpoints = process.env.TARGET_ADDITIONAL_FORWARD_ENDPOINTS || '';
const parseEndpoints = (endpointsStr) => {
const endpoints = [];
if (endpointsStr) {
endpointsStr.split(',').forEach((ep) => {
const lastSemicolonIndex = ep.lastIndexOf(';');
const url = ep.substring(0, lastSemicolonIndex);
const method = ep.substring(lastSemicolonIndex + 1).toUpperCase();
const parsedUrl = new URL(url);
endpoints.push({
hostname: parsedUrl.hostname,
port: parsedUrl.port || 80,
path: parsedUrl.pathname + parsedUrl.search,
method,
});
});
}
return endpoints;
};
const endpointsList = parseEndpoints(forwardEndpoints);
app.get('/health', (req, res, next) => {
const target = process.env.TARGET_HOSTS_DNS_NAME;
if (target === undefined) {
return next(new Error("Environment variable TARGET_HOSTS_DNS_NAME is not set"));
}
dns.lookup(target, { all: true }, (err, addresses) => {
if (addresses === undefined) {
return next(new Error("Unable to resolve hostname '" + target + "'."));
}
res.send(addresses);
});
});
app.all('*', (req, res, next) => {
dns.lookup(process.env.TARGET_HOSTS_DNS_NAME, { all: true }, (err, addresses) => {
if (addresses === undefined) {
return next(new Error("Unable to resolve hostname '" + process.env.TARGET_HOSTS_DNS_NAME + "'."));
}
const promises = [];
addresses.forEach((address) => {
promises.push(new Promise((resolve, reject) => {
if (req.headers.host !== undefined) {
delete req.headers.host;
}
const options = {
hostname: address.address,
port: process.env.TARGET_HOSTS_PORT,
path: req.url,
method: req.method,
headers: req.headers,
};
console.log(
"Sending %s request to http://%s:%d%s with headers: %s",
options.method,
options.hostname,
options.port,
options.path,
JSON.stringify(options.headers)
);
http
.request(options, (resp) => {
const chunks = [];
resp.on('data', (data) => chunks.push(data));
resp.on('end', () => {
let resBody = Buffer.concat(chunks);
switch (resp.headers['content-type']) {
case 'application/json':
resBody = JSON.parse(resBody);
break;
}
console.log(
"Got response for call: http://%s:%d%s -> %d: %s",
options.hostname,
options.port,
options.path,
resp.statusCode,
resp.statusMessage
);
resolve({
...options,
statusCode: resp.statusCode,
statusMessage: resp.statusMessage,
body: resBody.toString(),
});
});
})
.on('error', (err) => {
console.log('Error: ' + err.message);
resolve({
...options,
err: err,
});
})
.end();
}));
});
endpointsList.forEach((endpoint) => {
promises.push(new Promise((resolve, reject) => {
const options = {
hostname: endpoint.hostname,
port: endpoint.port,
path: endpoint.path,
method: endpoint.method,
headers: req.headers,
insecureHTTPParser: true
};
console.log(
"Sending %s request to http://%s:%d%s with headers: %s",
options.method,
options.hostname,
options.port,
options.path,
JSON.stringify(options.headers)
);
const reqForward = http.request(options, (resp) => {
const chunks = [];
resp.on('data', (data) => chunks.push(data));
resp.on('end', () => {
let resBody = Buffer.concat(chunks);
switch (resp.headers['content-type']) {
case 'application/json':
resBody = JSON.parse(resBody);
break;
}
console.log(
"Got response for call: http://%s:%d%s -> %d: %s",
options.hostname,
options.port,
options.path,
resp.statusCode,
resp.statusMessage
);
resolve({
...options,
statusCode: resp.statusCode,
statusMessage: resp.statusMessage,
body: resBody.toString(),
});
});
});
reqForward.on('error', (err) => {
console.log('Error: ' + err.message);
resolve({
...options,
err: err,
});
});
if (req.body) {
reqForward.write(JSON.stringify(req.body));
}
reqForward.end();
}));
});
Promise.all(promises)
.then((data) => {
console.log(data);
res.send(data);
})
.catch((err) => res.status(400).send(err));
});
});
app.listen(port, '0.0.0.0', () => {
console.log(`Listening on port ${port}...`);
});