Issues about session sharing in load balancing

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When doing load balancing the access page will distribute the access to different servers, the session is present on the server side, if the first access is distributed to a server, then the session will be saved to a server, Load balancer will be distributed to B server on re-access so the session information of the first visit will not get the previous session information. There are several ways to resolve this:

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(a) When using Nginx load Balancing can be configured Ip_hash to solve, Ip_hash technology can be a request for an IP to direct to the same back-end application server.

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This allows the same IP request to be distributed to the same back-end server.

Cons: If the server is down, then the user mapped to this server is depressed.

(ii) Synchronization session with database

This method is not advisable, mainly to put the session into the database, which will increase the burden of the database. For the time being, don't repeat ...

(c) The principle of synchronizing session data with cookies is as follows

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The code is as follows:

A server

<?php
Session_Start ();
if (isset ($_session[' username ')) {
Echo ' OK you can go next ';
}else if (isset ($_cookie[' username ')) {
Echo ' session is not in this server but the cookie is exist ';
$_session[' username ']=$_cookie[' username '];
}else{
Echo ' Cookie and session does\ ' t in this server ';
$_session[' username ']= ' Lampol ';
Setcookie (' username ', ' Lampol ', Time () +30*24*60*60);
}
Echo ' </br> ';
Echo ' This is A server ';
Echo ' </br> ';
Var_dump ($_session);

b Server

<?php
Session_Start ();
if (isset ($_session[' username ')) {
Echo ' OK you can go next ';
}else if (isset ($_cookie[' username ')) {
Echo ' session is not in this server but the cookie is exist ';
$_session[' username ']=$_cookie[' username '];
}else{
Echo ' Cookie and session does\ ' t in this server ';
$_session[' username ']= ' Lampol ';
Setcookie (' username ', ' Lampol ', Time () +30*24*60*60);
}
Echo ' </br> ';
Echo ' This is B server ';
Echo ' </br> ';
Var_dump ($_session);

And then start accessing

The first visit to Server B does not have session and cookie data and will then be saved to session and local cookie

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Refresh the second access distribution to the a server session does not exist but the cookie is locally present and the local cookie is synchronized to the B server's cookie

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Cons If you disable cookies then you're screwed.

(iv) Memcache or Redis storage session (take Memcache as an example)

Install the memcache and the client and the server, and then

<?php

Ini_set ("Session.save_handler", "memcache");
Ini_set ("Session.save_path", "192.168.1.142:11211");

The above configuration can be configured again in php.ini
Session_Start ();
$_session[' username ']= ' Lampol ';

This saves the session information in the Memache (Redis's same)

And then in the run

<?php
Ini_set ("Session.save_handler", "memcache");
Ini_set ("Session.save_path", "192.168.1.142:11211");
Session_Start ();
$mem = new Memcache;

$mem->connect (' 192.168.1.142 ', 11211);

$id =session_id ();

echo $mem->get ($id);

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Gets the data in the memcache of the session

In fact, if you consider the session sharing problem, there is absolutely no need to save the session directly to the data stored in the memcache can

Distributed directly to the same Memcache server can be, in addition memcache can master from, later in the article to continue to explore this issue.

This article is from the "Ideal for Life" blog, please be sure to keep this source http://lampol.blog.51cto.com/11662628/1852600

Issues about session sharing in load balancing