LoadBalancer

Load Balancing using Ldirectord on Linux (Apache) web server

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For this setup, we need four nodes (two Apache nodes and two load balancer nodes) and five IP addresses: one for each node and one virtual IP address that will be shared by the load balancer nodes and used for incoming HTTP requests.

I will use the following setup here:

Apache node 1: webserver1.tm.local (webserver1) – IP address: 192.168.0.103; Apache document root: /var/www
Apache node 2: webserver2.tm.local (webserver2) – IP address: 192.168.0.104; Apache document root: /var/www
Load Balancer node 1: loadb1.tm.local (loadb1) – IP address: 192.168.0.101
Load Balancer node 2: loadb2.tm.local (loadb2) – IP address: 192.168.0.102
Virtual IP Address: 192.168.0.105 (used for incoming requests)

In this tutorial I will use Ubuntu 8.04 LTS for all four nodes, just install basic Ubuntu 8.04 LTS on all four nodes. I want to say first that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you! I also recommend you to have a DNS server in place.

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UDP Load Balancing using PEN

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First setup PEN load balancer using this document.

After that, keep digging below 🙂

And that’s it, so now if we run pen we see it now has UDP support.

root@penudp:~/pen-0.18.0# pen
usage:
pen [-C addr:port] [-X] [-b sec] [-S N] [-c N] [-e host[:port]]
[-t sec] [-x N] [-w dir] [-HPWadfhrs]
[-o option]
[-E certfile] [-K keyfile]
[-G cacertfile] [-A cacertdir]
[-Z] [-R] [-L protocol]
[host:]port h1[:p1[:maxc1[:hard1[:weight1[:prio1]]]]] [h2[:p2[:maxc2[:hard2[:weight2[:prio2]]]]]] ...
-B host:port abuse server for naughty clients
-C port control port
-T sec tracking time in seconds (0 = forever) [0]
-H add X-Forwarded-For header in http requests
-U use udp protocol support

Now to test this I have just brought up a couple of DNS servers running bind.

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Understanding NAT, Direct Routing & Tunneling

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Virtual Server via NAT
The advantage of the virtual server via NAT is that real servers can run any operating system that supports TCP/IP protocol, real servers can use private Internet addresses, and only an IP address is needed for the load balancer.

The disadvantage is that the scalability of the virtual server via NAT is limited. The load balancer may be a bottleneck of the whole system when the number of server nodes (general PC servers) increase to around 20 or more, because both the request packets and response packets are need to be rewritten by the load balancer. Supposing the average length of TCP packets is 536 Bytes, the average delay of rewriting a packet is around 60us (on Pentium processor, this can be reduced a little by using of higher processor), the maximum throughput of the load balancer is 8.93 MBytes/s. Assuming the average throughput of real servers is 400Kbytes/s, the load balancer can schedule 22 real servers.

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PEN: HTTP Load Balancer

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This is performed on a CentOS 6.x 64 bit machine

Install pen which is lightweight simple Load Balancing software.

It is TCP protocol based, so it’s possible to balance not only HTTP but SMTP, FTP, LDAP and so on. This example is based on the environment like follows.

Pen-LB-Capture

Configure Pen to load balance to Backend#1, Backend#2, Backend#3 web servers.

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Open Sourced Load Balancer

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Linux Virtual Server
The Linux Virtual Server Project is a project to cluster many real servers together into a highly available, high-performance virtual server. The LVS load balancer handles connections from clients and passes them on the the real servers (so-called Layer 4 switching) and can virtualize almost any TCP or UDP service, like HTTP, HTTPS, NNTP, FTP, DNS, ssh, POP3, IMAP4, SMTP, etc. It is fully transparent to the client accessing the virtual service.
Homepage: http://www.LinuxVirtualServer.org/

BalanceNG
BalanceNG is a modern software IP load balancing solution. It is small, fast, and easy to use and setup. It offers session persistence, different distribution methods (Round Robin, Random, Weighted Random, Least Session, Least Bandwidth, Hash, Agent, and Randomized Agent) and a customizable UDP health check agent in source code. It supports VRRP to set up high availability configurations on multiple nodes. It supports SNMP, integrating the BALANCENG-MIB with Net-SNMPD. It implements a very fast in-memory IP-to-location database, allowing powerful location-based server load-balancing.
Homepage:http://www.inlab.de/balanceng/

HAproxy 
HAproxy is a high-performance and highly-robust TCP and HTTP load balancer which provides cookie-based persistence, content-based switching, advanced traffic regulation with surge protection, automatic failover, run-time regex-based header control, Web-based reporting, advanced logging to help trouble-shooting buggy applications and/or networks, and a few other features. Its own event-driven state machine achieves 20,000 hits per second and surpasses GigaEthernet on modern hardware, even with tens of thousands of simultaneous connections.
Homepage:http://haproxy.1wt.eu/

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CentOS: Configure Piranha as Load Balancer (Direct Routing Method)

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I am currently working on a web cluster project using CentOS. In this project, I have 2 web servers running on Apache and mounted the same document root to serve the HTTP content. I also have 2 servers in front of it to become the load balancer and failover to increase high availability of the two-node web server cluster. The virtual IP will be hold by load balancer #1 with auto failover to load balancer #2.

You may refer to diagram below to get clearer picture:

I am using following variables:

All servers’ OS: CentOS 6.2 64bit
Web server #1: 192.168.0.221
Web server #2: 192.168.0.222
Load balancer #1: 192.168.0.231
Load balancer #2: 192.168.0.232
Virtual IP: 192.168.0.220

Load Balancer Server
1. All steps should be done in both servers unless specified. We will install Piranha and other required packages using yum:

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Load Balanced IIS behind ldirectord loadbalancer

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Cluster Nodes Configurations (IIS6/7 Real Web Server Configuration)

1. Create text file by using Notepad and name it "check.txt"
2. Fill this file with "webserverisworking" string.
3. Move file to "C:\inetpub\wwwroot" or anywhere your web files are.

If you are using Windows XP/2003 IIS web server then you should do these steps:

1. Install "Microsoft Loopback Adapter" by using "Add Hardware" icon in Control Panel.
2. Set IP to 10.10.10.53
3. Set Subnet Mask to 255.255.255.0
4. Don't Set Gateway or DNS
5. Done!

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