It's a subset of Edge Side Include standard implemented with promise-based interface.
Let's say you want to use ESI in your project, but also want to retain good developer experience.
Rather than having to configure Varnish or Ngnix to take care of server-rendered ESI tags locally you can simply pass the server output through esi.process
function right before pushing it out to the client.
var response = obtainServerResponseWithEsiTags();
return Promise.resolve()
.then(function() {
if(process.env.NODE_ENV !== 'production') {
return esi.process(response);
}
return response;
});
It also improves code mobility - if for whatever reason you decide to move from ESI-enabled environment into one that doesn't support it (yet?), all you have to do is to process the response directly on the server. This module should be performant enough for that use case.
- Support for
<esi:include>
tags- support for
alt
as fallback URL
- support for
- Out of the box Express support
- Custom logging
- Lots of good stuff like caching, retires, request collapsing and such provided by Good Guy HTTP
…and more, take a look at test cases for complete list.
nodesi
does not support the entire ESI spec, but aims to provide a usable subset. This includes, of course <esi:include src="…">
, but also some more advanced features like:
<esi:include src="http://example.com/1.html" alt="http://bak.example.com/2.html"/>
Will try to include http://example.com/1.html
first, and if that fails, fall back to http://bak.example.com/2.html
. If both requests fail, the standard error handling described below will kick in.
npm install nodesi
var ESI = require('nodesi');
var esi = new ESI({
allowedHosts: ['http://full-resource-path']
});
esi.process('<esi:include src="http://full-resource-path/stuff.html" />').then(function(result) {
// result is a fetched html
});
var esiMiddleware = require('nodesi').middleware;
var app = require('express')();
// inject the middleware before your route handlers
app.use(esiMiddleware());
All the ESI constructor options described below are also applicable for middleware function.
Just pass them like that: esiMiddleWare({baseUrl: ..., allowedHosts: [...]});
If you'd like to pass options like headers to ESI middleware, use req.esiOptions
object:
...
app.use(esiMiddleware());
app.get('/example', function(req, res) {
req.esiOptions = {
headers: {
'Authorization': 'Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ=='
}
};
res.render('example');
});
If you'd like to adjust the baseUrl dynamically, use req.esiOptions
object:
...
app.use(esiMiddleware());
app.get('/example', function(req, res) {
req.esiOptions = {
baseUrl: req.url
};
res.render('example');
});
var ESI = require('nodesi');
var esi = new ESI({
baseUrl: 'http://full-resource-path'
});
esi.process('<esi:include src="/stuff.html" />').then(function(result) {
// result is a fetched html
});
var ESI = require('nodesi');
var esi = new ESI({
baseUrl: 'http://full-resource-path'
});
esi.process('<esi:include src="/stuff.html" />', {
headers: {
'Authorization': 'Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ=='
}
}).then(function(result) {
// result is a fetched html
});
Since this module performs HTTP calls to external services, it is possible for a malicious agent to exploit that, especially if content of a esi:include tag can be provided by user.
In order to mitigate that risk you should use allowedHosts
configuration option. It's supposed to be a list of trusted hosts (protocol + hostname + port), represented as strings or regular expressions.
var esi = new ESI({
allowedHosts: ['https://exact-host:3000', /^http(s)?:\/\/other-host$/]
});
If you're using baseUrl
option then it's host will automatically be added to allowedHosts
.
In case some url gets blocked you'll receive an error in your onError
handler (see below) with blocked
property set to true
.
You can provide onError callback to a ESI constructor. It will recieve two arguments: source URL and error object.
It should return a string that will be put in place of errorous content.
var esi = new ESI({
onError: function(src, error) {
if(error.statusCode === 404) {
return 'Not found';
}
return '';
}
});
It's a common anti-pattern that libraries write to stdout w/o users permission.
We want to be nice so you can provide your own logging output with logTo
configuration option.
It's expected to be an object with "write" method on it that accepts a single string.
Logging to a custom object
var esi = new ESI({
logTo: {
write: function(log) {
// do some stuff with log string here
}
}
});
Logging to a standard output (same as console.log):
var esi = new ESI({
logTo: process.stdout
});
Logging to a file (possible, but please don't do that):
var logFile = require('fs').createWriteStream('./log.txt');
var esi = new ESI({
logTo: logFile
});
You can run performance tests with npm run perf [args]
This tool assumes you have Siege installed and added to your Path variable.
[args] are list of arguments that will be passed to Siege.
nodesi
is made available under the conditions of the ISC license