Transparent HTTP proxy. Dynamically mounts proxy targets on an existing HTTP server instance.
This module is intended for internal use in Podium and is not a module an end user would use directly. End users will typically interact with this module through higher level modules such as the @podium/layout and @podium/podlet modules.
$ npm install @podium/proxyAttach a proxy target to an HTTP server.
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
// Set up proxy
const proxy = new Proxy();
// Register remote target(s) on separate namespace
proxy.register({
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
},
version: '1.0.0',
content: '/bar',
});
// Attach proxy to http server
const app = http.createServer(async (req, res) => {
const incoming = new HttpIncoming(req, res);
const result = await proxy.process(incoming);
// The proxy did return "undefined" so nothing matched our proxy
if (!result) {
res.statusCode = 404;
res.end('404 - Not found');
}
});
// Start appserver where proxy is attached
app.listen(9999);Proxy is now mounted on: http://localhost:9999/podium-resource/bar/api
Create a new Proxy instance.
import Proxy from '@podium/proxy';
const proxy = new Proxy(options);The constructor takes the following arguments:
An options object containing configuration. The following values can be provided:
pathname- {String} - Pathname to the root of where the proxy is to be mounted. Default:/.prefix- {String} - Prefix used to namespace the proxy so its isolated from other routes in a HTTP server. Appended after pathname. Default:podium-resource.timeout- {Number} - Default value, in milliseconds, for how long a request should wait before the connection is terminated. Default: 6000maxAge- {Number} - Default value, in milliseconds, for how long manifests should be cached. Default: Infinitylogger- {Object} - A logger which conforms to the log4j interface. See the docs for abstract logger for more information.
The Proxy instance havs the following API:
Registers proxy target(s) by providing a Podium manifest.
Example:
import Proxy from '@podium/proxy';
// Set up proxy
const proxy = new Proxy();
// Register remote target(s) on separate namespace
proxy.register('podlet-name-in-layout', {
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
},
version: '1.0.0',
content: '/bar',
});Name for the registered podlet. This will be part of the URL to distinguish the podlets proxy endpoints in the URL space.
A Podium manifest where the proxy property is given. The proxy property is
an object where the key identifies the target and the property is a URI to
the target.
Metod for processing a incoming HTTP request. Matches the request against the registered routing targets and proxies the request if a match is found.
Returns a promise. When resolving the passed in HttpIncoming object will be returned.
If the inbound request matches a proxy endpoint and a proxy request was
successfully performed, the .proxy property on the returned HttpIncoming
object will be true. If the inbound request did not yeld a proxy request, the
.proxy property on the returned HttpIncoming object will be false.
The method takes the following arguments:
An instance of an HttpIncoming class.
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
const proxy = new Proxy();
proxy.register({ ...[snip]... });
const app = http.createServer(async (req, res) => {
const incoming = new HttpIncoming(req, res);
const result = await proxy.process(incoming);
if (result.proxy) return;
res.statusCode = 404;
res.end('404 - Not found');
});Property that exposes a metric stream.
Exposes a single metric called podium_proxy_request which includes podlet
and proxy meta fields.
Please see the @metrics/client module for full documentation.
Returns an Array of all loaded manifests ready to be used by .load().
Loads an Array of manifests (provided by .dump()) into the proxy. If any of
the items in the loaded Array contains a key which is already in the cache, the
entry in the cache will be overwritten.
If any of the entries in the loaded Array are not compatible with the format
which .dump() exports, they will not be inserted into the cache.
Returns an Array with the keys which were inserted into the cache.
To be able to have multiple proxy targets in an HTTP server we need to make sure that they do not collide with each other. To prevent this, each proxy target defined is mounted on its own separate namespace in an HTTP server.
The convention for these namespaces is as follow:
{pathname}/{prefix}/{podletName}/{proxyName}/
- pathname - Defined by the
pathnameargument in the constructor. Defaults to/. - prefix - Defined by
prefixargument in the constructor. Defaults topodium-resource. - podletName - Defined by the
namevalue in the manifest. Note: When the proxy module subscribes to receive manifest updates from the Podium Client, this name will be the name a Podlet is registered with in the Podium Client. - proxyName - Defined by the
proxy.nameproperty defined in the manifest.
If one has the following manifest defined in an express server:
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
const proxy = new Proxy();
proxy.register({
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
},
version: '1.0.0',
content: '/index.html',
});
const app = http.createServer(async (req, res) => {
...[snip]...
});
app.listen(8000);The following proxy targets will be mounted:
If one has the following manifest and overrides the prefix on the constructor:
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
const proxy = new Proxy({
prefix: '/my-proxy',
});
proxy.register({
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
},
version: '1.0.0',
content: '/index.html',
});
const app = http.createServer(async (req, res) => {
...[snip]...
});
app.listen(8000);The following proxy targets will be mounted:
If one has the following manifest defined in an express server:
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
const proxy = new Proxy();
proxy.register({
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
feed: '/feed',
},
version: '1.0.0',
content: '/index.html',
});
const app = http.createServer(async (req, res) => {
...[snip]...
});
app.listen(8000);The following proxy targets will be mounted:
If one has the following manifests defined in an express server:
import { HttpIncoming } from '@podium/utils';
import Proxy from '@podium/proxy';
import http from 'http';
const proxy = new Proxy();
proxy.register({
name: 'bar',
proxy: {
api: 'http://www.external.com/some/path',
feed: '/feed',
},
version: '1.0.0',
content: '/index.html',
});
proxy.register({
name: 'foo',
proxy: {
users: 'http://www.anywhere.com/api',
},
version: '2.0.0',
content: '/index.html',
});
const app = http.createServer(async (req, res) => {
...[snip]...
});
app.listen(8000);The following proxy targets will be mounted:
- http://localhost:8000/podium-resource/bar/api/
- http://localhost:8000/podium-resource/bar/feed/
- http://localhost:8000/podium-resource/foo/users/
Copyright (c) 2019 FINN.no
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