I would like to try and improve site render times by making use of preload/push headers.
We have various assets which are required up front that I would like to preload, and various assets which are marked up in data attributes etc which will be required later via JS but not for initial paint. It would be good to get these flowing to the client early.
Our application is a bit of a hybrid, it uses http-proxy-middleware connected to various different applications, plus directly renders pages it self. I would like the middleware to be agnostic and work regardless of how to page is produced.
I've seen express-mung but this doesn't hold back the header so executes too late, and works with chunked buffers anyway not the entire response. Next up was express-interceptor, that works perfectly for pages rendered directly in express but causes request failures for pages run through the proxy. My next best idea is pulling apart the compression module to figure out how it works.
Does anyone have a better suggestion, or even better know of a working module for this kind of thing?
Thanks.
I have always wondered how can I do this..
if you go https://community.nodebb.org/topic/14103/strange-thing-on-this-forum
It shows a thread in a forum.
But you can actually access to that same page with https://community.nodebb.org/topic/14103
and then this url changes to the 1st one above.
How can I do this in Node.js?
Node itself is just the language, what you're asking about happens in a framework, like Express.
In Express (and most other frameworks) you can define routes based on either strings, symbols, or a regex. In your above example, the route definition is likely looking for topic/:id and also set to accept anything put after the ID.
Look at the basics of Routing in Express to see how this works.
I'm fairly new to programming and this question is about making sure I get the HTTP protocol correctly. My issue is that when I read about HTTP request/response, it looks like it needs to be in a very specific format with a status code, HTTP version number, headers, a blank line followed by the body.
However, after creating a web app with nodejs/express, I never once had to actually write code that made an HTTP response in this format (I'm assuming, although I don't know for sure that other frameworks like ruby on rails or python/Django are the same). In the express app, I just set up the route handlers to render the appropriate pages, when a request was made to that route.
Is this because express is actually putting the response in the correct HTTP format behind the scenes? In other words, if I looked at the expressJS code, would there be something in that code that actually makes an HTTP response in the HTTP format?
My confusion is that, it seems like the HTTP request/response format is so important but somehow I never had to write any code dealing with it for a node/express application. Maybe this is the entire point of a framework like express... to take out the details so that developers can deal with business logic. And if that is correct, does anyone ever write web apps without a framework to do this. Would you then be responsible for writing code that puts the server's response into the exact HTTP format?
I'm fairly new to programming and this question is about making sure I get the HTTP protocol correctly. My issue is that when I read about HTTP request/response, it looks like it needs to be in a very specific format with a status code, HTTP version number, headers, a blank line followed by the body.
Just to give you an idea, there are probably hundreds of specifications that have something to do with the HTTP protocol. They deal with not only the protocol itself, but also with the data format/encoding for everything you send including headers and all the various content types you can send, authentication schemes, caching, status codes, URL decoding, etc.... You can see some of the specifications involved just by looking here: https://www.w3.org/Protocols/.
Now a simple request and a simple text response could get away with only knowing a few of these specifications, but life is not always that simple.
Is this because express is actually putting the response in the correct HTTP format behind the scenes? In other words, if I looked at the expressJS code, would there be something in that code that actually makes an HTTP response in the HTTP format?
Yes, there would. A combination of Express and the HTTP library that is built into node.js handle all the details of the specification for you. That's the advantage of using a library/framework. They even handle different versions of the protocol and feedback from thousands of other developers have helped them to clean up edge case bugs. A good library/framework allows you to still control any detail about the response (headers, content types, status codes, etc..) without making you have to go through the detail work of actually creating the exact response. This is a good thing. It lets you write code faster and lets you ride on the shoulders of others who have already figured out minutiae details that have nothing to do with the logic of your app.
In fact, one could say the same about the TCP protocol below the HTTP protocol. No regular app developer wants to write their own TCP stack. Instead, you just want a working TCP stack that you can use that's already been tuned and debugged for you.
However, after creating a web app with nodejs/express, I never once had to actually write code that made an HTTP response in this format (I'm assuming, although I don't know for sure that other frameworks like ruby on rails or python/Django are the same). In the express app, I just set up the route handlers to render the appropriate pages, when a request was made to that route.
Yes, this is a good thing. The framework did the detail work for you. You just call res.setHeader(), res.status(), res.cookie(), res.send(), res.json(), etc... and Express makes the entire response for you.
And if that is correct, does anyone ever write web apps without a framework to do this. Would you then be responsible for writing code that puts the server's response into the exact HTTP format?
If you didn't use a framework or library of any kind and were programming at the raw TCP level, then yes you would be responsible for all the details of the HTTP protocol. But, hardly anybody other than library developers ever does this because frankly it's just a waste of time. Every single platform has at least one open source library that does this already and even if you were working on a brand new platform, you could go get an open source body of code and port it to your platform much quicker than you could write all this yourself.
Keep in mind that one of the HUGE advantages of node.js is that there's an enormous body of open source code (mostly in NPM and Github) already prepackaged to work with node.js. And, because node.js is server-side where code memory isn't usually tight and where code just comes from the local hard disk at server init time, there's little downside to grabbing a working and tested package that does what you already need, even if you're only going to use 5% of the functionality in the package. Or, worst case, clone an existing repository and modify it to perfectly suit your needs.
Is this because express is actually putting the response in the
correct HTTP format behind the scenes?
Yes, exactly, HTTP is so ubiquitous that almost all programming languages / frameworks handle the actual writing and parsing of HTTP behind the scenes.
Does anyone ever write web apps without a framework to do this. Would
you then be responsible for writing code that puts the server's
response into the exact HTTP format?
Never (unless you're writing code that needs very low level tweaking of HTTP code or something)
Due to some limitations about the web services I am proxying, I have to inject some JS code so that it allows the iframe to access the parent window and perform some actions.
I have built a proxy system with node-http-proxy which works pretty nicely. However I have spent unmeasurable hours trying to modify the content (on my own, using harmon as well, etc) that is being sent to the user without any success. I have found some articles and even some questions here but all of them are outdated and are not useful anymore.
I was wondering if someone can give me an actual example about how to do this, because I am unable to do it and maybe it is just that it is impossible to do at this point?
I haven't tried harmon, but I did try cheerio and it works.
However, I used http-mitm-proxy and not node-http-proxy.
If you are using http-mitm-proxy, you need to return a promise in the response handler. Otherwise, the proxy continues to send the original response without picking up your changes.
I have recently written another proxy at:
https://github.com/noeltimothy/noelsproxy
I'm going to add response handling to this soon. This one uses a callback mechanism, which means it wont return the response until the caller signals it to.
You should be able to use 'cheerio' and alter the content in JQuery style.
I have an express based app serving server side rendered HTML from handlebars templates, and a bundle of the backbone resources. Theoretically, client side, the app resembles what is happening server side.
This is all fine in development, but when the node server is dealing with many requests at the same time, then the mechanism by which the helper we are using is defined/redefined breaks - we set the helper (in this case logged in / not logged in, but could be anything) then serving the rest of the request happens asynchronously - we don't know and cannot control how long this will take.
I have already figured out that this is because Handlebars on the server is effectively a global - so every time a request comes in, the helper that is being called is from there, a shared object between requests.
The question is, how to be able to set a helper per async request that returns that particular value, and does not get polluted by concurrent requests...?
Here's a gist of a test case - hopefully shows the problem:
https://gist.github.com/dazld/023df6e1da7a92387720
(if it is not obvious from that what i am going for, just ping in comments, and i will write up something clearer).
Thanks!
This is because your using a single instance of Handlebars and with lots of requests your polluting one request with another.
I use hbs (https://github.com/donpark/hbs) as it creates a new instance of handlebars for each request/render for you.