caching configuration microcaching nginx SSI module web-server

SSI module : Date wise caching in Nginx

Hi everyone, today we are going to see how to implement date wise caching in Nginx using SSI module. There happen to be time when we want to refresh the cache as soon as new date comes. That is, we need such caching when we have our content as static but only for a specific date and it changes with new date.

For the date-wise caching, it doesn’t need actually a lot of work. You just need to change the fastcgi_cache_key and append date as well. For the date, we can use $date_local variable in nginx. But the problem comes as $date_local contains time as well, it is in non readable format, just numbers, (we can’t rewrite it).

SSI module comes for the rescue here. SSI module is a great implementation in nginx which processes SSI(Server Side Include) commands in the response to be sent. We can format the $date_local variable using this, to a readble form and even modify it for just the date.

Then we can use $date_local variable and append it with cache_key. Please follow below to see some codes of how to achieve it.

server {

ssi on;

location ~ \.php$ {

fastcgi_cache_key $your_key|$date_local;



Now, in somewhere in your view(response to be sent) html tag include below ssi command,

less than html greater than

less than!–# config timefmt=”%A, %d-%b-%Y” –greater than

less than/html greater than

Now, above command will be executed by Nginx before it is sent to client. It changes the $date_local default format to the desired format. And so your cache_key will be generated date-wise. As soon as, new date comes a new cache will be generated, and for the same date, the response from the cache will be served.

So now with the help of SSI module of Nginx, date wise caching can be easily done.
Read my article here for how to install nginx from source, which is needed to install third party module(SSI module) for Nginx.

configuration install modules nginx source ubuntu

Install Nginx from Source in Ubuntu

Hello Everyone, the very handy command to ubuntu users installing nginx, sudo apt-get install nginx, that’s it. It does install nginx on your machine, with almost all the modules usually needed by the users, super awesome. The shortcoming of this method of installing nginx is that if you want to add more modules to the nginx, you just can’t do it. Currently, nginx installed from apt-get do not support adding custom modules to it. Now when you look over internet about how to add module in nginx, it suggests you to install nginx from source. Some times it gets so much confusing, there is something, which always holds developer back to install it this way(As they already had an easy way).

So here I will show you that installing nginx from source is as easy as the apt-get(almost) and interesting as well. Lets do it,

1. Find the stable version of Nginx (, current stable version) compatible with your custom module you need to add(if the module doesn’t support all versions of nginx) from its download page. (tar file used here)

2. open terminal

3. sudo apt-get install build-essential libpcre3 libpcre3-dev libssl-dev (install the tools required to compile nginx from source)

4. sudo su (get the super user privilege).

5. mkdir nginx (create a directory named nginx{not necessarily}, all the work will be done into this directory)

6. cd nginx (get into nginx directory)

7. wget (download your compatible version of nginx)

8. tar -xzvf nginx-1.10.2.tar.gz(extract the downloaded content)

9. cd nginx-1.10.2 (get into nginx directory)

10. ./configure (run the configure file)

11. make & make install (google to know about them at your will, I got to work for that or just run them)

12. sudo /usr/local/nginx/sbin/nginx -s stop (stop the nginx server if already running)

13. sudo /usr/local/nginx/sbin/nginx (start the nginx server)

14. enter the ip of your server, and you must be able to see the default nginx page.

So, that’s it. You have now installed your nginx from source.
Now, the commands for starting and stopping and the locations of the config files are different than /etc/nginx. The nginx files are kept in /usr/local/nginx.

Configuration file: /usr/local/nginx/conf/nginx.conf
Start server : /usr/local/nginx/sbin/nginx
Stop server: /usr/local/nginx/sbin/nginx -s stop
Reload server : /usr/local/nginx/sbin/nginx -s reload
Other commands you can find by tabbing after -s or reading the /usr/local/nginx/sbin/nginx file.

Now you can add any module to your nginx, by compiling nginx with the module. Go ahead and learn and test different great available modules of nginx. One with which I’m currently fascinated with is rtmp module.

1. Each time you are adding a module, make sure you add all other modules(which you earlier had compiled with and still need them) as well.

2. Each time after the module is added, restart the nginx i.e., stop and start, rather than reload.

analytics chat chatting google google-analytics javascript live live-users long-polling nginx node.js performance persistent persistent-connection php5-fpm Proxy real-time response reverse-proxy socket socks tcp upstream web-server websocket websocket-handshake

How To Make Your Own Analytics Tool?

An analytics tool is a tool that you can use to get the information about how is your website performance, how are the users using it, what are the number of users at anytime(live users), live users for different urls, and other infos. One such example of the tool is the google analytics.

Analytics tool

Analytics tool gives a lot of information about your website with the nice looking graphs and all. In this blog, we will be discussing how we can make such analytics tool(digging the data).

Question 1: Why should we make such thing if it already exists?

Answer : One reason is that it is not free for always. The other reason is that the process of making it is very sexy and you learn technologies that you can use to make your own other real time apps like chatting app. Now that is more a valid reason.

Question 2: What are we talking about?

Answer : This is an example of a real time application. You see, you are tracking live users’ data. The data can be anything like total number of users anytime or number of users for different urls or different referral or different user agent or different visited ips, or anything. The other example of a real time application is a chatting application where a lot of users are communicating at the same time.

Question 3: What technologies are used for such an application?

Answer : So we need a continuous stream of response from the server about their performance as only servers know what is hitting them. It can only be achieved if there is some persistent connection between client and server so that server can continuously push data to the client. With persistent connection I would mean one for literally persistent connection(web sockets) or else timed persistent connection(long polling) or else chunk persistent connection(polling). By timed persistent connection, I mean persistent connection only for certain time interval after which it is closed and again opened. And by chunk persistent connection, I mean lots of request with no persistency, but the requests are so frequent that altogether they seem persistent(my bad).

Among all, I prefer web sockets, as I can’t logically satisfy myself why to use others and more of it that they are the outdated styles and only existed when sockets were not there.

So in this tutorial we will be using library with node.js to create web sockets. Below are the other libraries with other language which I found from here.

Analytics tool

And yes, we are going to use Nginx as a reverse proxy for web sockets. A very great tutorial regarding this can be found here. You can skip Nginx if you wish and directly test for your node.js server.

For Nginx configuration, as mentioned in tutorial,

server {
    location / {
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_pass http://socket_nodes;

Proper explanation is given in that tutorial for how this will work for sockets. Now we setup our Node server(server.js), a very nice tutorial can be found here.

var data = {};
var http = require(“http”);
var url = require(‘url’);
var fs = require(‘fs’);
var io = require(‘‘);
var path;
var server = http.createServer(function(request, response){
        console.log(‘Request Accepted’);
        path = url.parse(request.url).pathname;
            case ‘/’:
                response.writeHead(200, {‘Content-Type’: ‘text/html’});
                response.write(‘hello world’);
            case ‘/live’:
                fs.readFile(__dirname + ‘/socket_io.html’, function(error, data){
                    if (error){
                        response.write(“opps this doesn’t exist – 404”);
                        response.writeHead(200, {“Content-Type”: “text/html”});
                        response.write(data, “utf8”);
                response.write(“opps this doesn’t exist – 404  –“+path);
 var listener = io.listen(server);
 listener.sockets.on(‘connection’, function(socket){
    console.log(‘Socket Made.’);
        socket.emit(‘showdata’, {‘data’: data});
    }, 1000);
 socket.on(‘disconnect’, function(){
    console.log(“Socket Closed.”);

Load on the client side in your socket_io.html which will be used to create event to create a persistent connection. (Please don’t bang your head for how would it find


     var socket = io.connect(); // your initialization code here.
     socket.on('showdata', function(data){

Now you can see all the data in your browser’s console. You can put this data at the right place of your analytics html. Now you can easily send continuous data from node server to your client.

Are you still wondering how would we gather data? Suppose we want to track number of live users, for that we will use a key “live” in data variable and initialize with 0. We will increment it as soon as there is a socket made and decrement it as soon as the socket is closed(Make sure io.connect() is called once and only once for a page load). So the data[‘live’] will determine the number of live users.

In server.js,

listener.sockets.on(‘connection’, function(socket){
    console.log(‘Socket Made.’);
    data[‘live’] +=1;
        socket.emit(‘showdata’, {‘data’: data});
    }, 1000);
 socket.on(‘disconnect’, function(){
    console.log(“Socket Closed.”);

As simple as that. It is just the logics in node to be done and you can achieve any data. Now for temporary data(by temporary I mean the machine hosting node server is until rebooted), we don’t need any extra storage.

If we want to use some durable data, or store some information, we can choose database of our choice and send data from node to database.

Now we are also using Nginx as a reverse proxy which is helpful in load handling and better scaling. We can extract other information like user ip, upstream responses(php), and other valuable information and send to node.

So yes, it is really interesting to make such tool, I told you so. You are surely going to stuck in somewhere or make it up or for any suggestion or for confusion, we can always discuss.

Great to see you people with your own analytics tool. 🙂

ajax bidirectional chat chatting full-duplex http live live-users long-polling node.js persistent persistent-connection polling real-time response reverse-proxy socket tcp Uncategorized websocket websocket-handshake

Long Polling Vs Socket

There is no match, in the battle of Long Polling Vs Socket, Socket clearly wins.(As long as I’m the referee, for now).

Long Polling and Sockets are the two different, well known, ways to implement real time applications, like live users or chatting where you have to broadcast the changes instantaneously. This post is going to compare the two technologies for their use. You might feel that this post is being biased as I can’t make myself like Long Polling over Sockets. I will try to reason this biasness or more importantly the logical thinking why one should not prefer polling(short or long) over sockets.

Polling is a method where the client requests server like ajax, the difference is that it is set at timed interval which means every some second it requests the server for the response. It is also known as short polling. Long polling is another dirty trick with the same concept.

Long Polling is a method when the client makes ajax request to server but the server do not response instantaneously but instead it holds the response until there is some change in the database or else the request times out. (WTF, then what does it do with the persistent connection all the time before it times out). The trick here is that with long polling we are saving the number of unnecessary requests to the server which would been made for no change in data.

Socket is a method when the client sends a WebSocket handshake request, for which the server returns a WebSocket handshake response. The handshake resembles HTTP so that servers can handle HTTP connections as well as WebSocket connections on the same port. Once the connection is established, communication switches to a bidirectional binary protocol that does not conform to the HTTP protocol. Once the connection is established, the client and server can send WebSocket data or text frames back and forth in full-duplex mode. The data is minimally framed, with a small header followed by payload.

Lets start.

First of all, Long Polling is an outdated method and Socket is the future. Long Polling was used as a trick for polling when sockets were not there.

This makes your client’s browser slow or might hang it up as at every interval there is a ajax request done. This also looks suspicious to the client(what is it that being requested from my browser, why my browser consumes so much memory).

This also increases server load, as there are requests at continuous intervals. It is like timed persistent connection because until the server generates response or else timeout, connection is kept alive and after the response received, another request for persistent connection is generated. So why not create it once and for all. For each request there is an overload of TCP connection handshake which is minimized to single handshake. As there are multiple requests so the overload of payload will also be there.

Long polling maintains a loop which constantly checks for change in database which only decides whether to response back to client. In Node.js, you can share the same memory for different socket connections, so that way they can access shared variables. So you don’t need to use database as exchange point in the middle (like with AJAX or Long Polling). You can store data in RAM, or even republish between sockets straight away.

With AJAX(Long polling) there is a higher chance of MITM as each request is new TCP connection and traversing through internet infrastructure. With WebSockets, once it’s connected it is far more challenging to intercept in between, with additionally enforced frame masking when data is streamed from client to server as well as additional compression, that requires more effort to probe data.

With long polling there is higher latency than sockets. Http is the stateless protocol, which means it forgets connection after the work is done, so there will be delay in response as it will have to make an all new request. But with socket, it reflects the change as soon as it detects.

Some nice links can be found hereherehere.

That’s it for today. You are most welcome to break the monotonicity of the fairness of socket over long polling.

Thanks Guys.