HAProxy load balancer, how, when, where to use.

1. HAProxy
ARINDAM NAYAK

2. Agenda
•What is HAProxy?
•When to use?
•Who uses HAProxy?
•Similar Products & comparisons
•Why HAProxy?
•Examples
•Where it can be used?
•Design consideration
•How to implement
•Benchmarking – Comparing metrics before implementing HAProxy and after implementation.
[ Above point will be covered in next sessions  ]

3. What is HAProxy?
HAProxy is a free, very fast and reliable solution offering
high availability, load balancing, and proxying for TCP and
HTTP-based applications
● Proxying
● Load balancing , Scale out, Failover ( Health Checks)
● High availability

4. When to use?
•Websites with very high loads.
•Multiple connection to website.
•Load Balancing required at HTTP and TCP level.
•Fault Tolerance
•Maximize Availability
•Maximize throughput
•Horizontal Scaling

5. Who uses HAProxy?
•Stack Overflow
•Server Fault
•GitHub
•Tumblr
•Twitter
•Imgur – Image hosting / sharing
•Instagram – Image hosting/sharing
•Reddit
………….
For more users, refer - http://www.haproxy.org/they-use-it.html

6. Similar Products & comparisons
•Nginx – Reverse proxy server , Load balancing , web server ..
•Linux Virtual server – Runs in kernel mode, routes packets. - "fast as hell", but rigid as the kernel
•Asp.Net WebFarm
•AWS Elastic Load Balancer – Works with AWS or servers under AWS VPC.
•F5 – Commercial
•Varnish – Primarily focused on HTTP
•……………….

7. Why HAProxy?
Out of band health checks – Monitors server health by sending requests at configured intervals
which are independent of incoming traffic
Works on TCP
More Algorithm option – Support more number of algorithm to select backend server.
Open Source product.
Speed. It’s really, really fast.
Hot reconfiguration – Don’t need to put in maintenance mode and change config.

8. Examples
•Load balance all png, jpg, gif requests to a specific server(s).
•Load balance all mov, avi, mkv requests to a specific server(s).
•Load balance users in South East US IP range to southeast.yoursite.com
•Proxying users by ranking (gold customers, silver, bronze).

9. Where it can be used?
•Linux 2.4 on x86, x86_64, Alpha, Sparc, MIPS, PARISC
•Linux 2.6 / 3.x on x86, x86_64, ARM, Sparc, PPC64
•Solaris 8/9 on UltraSPARC 2 and 3
•Solaris 10 on Opteron and UltraSPARC
•FreeBSD 4.10 - 10 on x86
•OpenBSD 3.1 to -current on i386, amd64, macppc, alpha, sparc64 and VAX (check the ports)
•AIX 5.1 - 5.3 on Power™ architecture

10. Design consideration
Need to segregate DB Server from App Server.

11. Design consideration
(Contd.)
Clustering DB server.
• All applications access the cluster via one single IP. The topology of the database cluster is masked
behind HAProxy.
• MySQL Connections are load-balanced between available DB nodes
• It is possible to add or remove database nodes without any changes to the applications.
• Once the max number of database connections (in MySQL) is reached, HAProxy queues additional new
connections. This is a neat way of throttling database connection requests and achieves overload
protection.
Managing sessions:
◦ Set up sticky session in HAProxy
◦ Use centralized session management like Redis, Memcache

12. How to implement
Download and install HAProxy.
Jump to config file and set following
◦ Access control list
◦ Bankend
◦ Frontend
Few Algorithm for selecting back-end server.
• Roundrobin - selects servers in turns. This is the default algorithm.
• Leastconn - Selects the server with the least number of connections--it is recommended for longer
sessions.
• Source- This selects which server to use based on a hash of the source IP i.e. your user's IP address. This
is one method to ensure that a user will connect to the same server.

13. How to implement
(Contd.)

14. How to implement
(Contd.)
Load balancers are generally grouped into two categories: Layer 4 and Layer 7. Layer 4
load balancers act upon data found in network and transport layer protocols (IP, TCP, FTP, UDP).
Layer 7 load balancers distribute requests based upon data found in application layer protocols
such as HTTP.
Node.Js App – HTTP Listener for different ports.
HAProxy to make reverse proxy for port – 80 to others listed above.
DEMO
Browser Console
Monitoring via Nagios, Scout

15. Benchmarking
Will be covered in next session.

16. Reference
•http://www.haproxy.org/
•https://www.digitalocean.com/community/tutorials/an-introduction-to-haproxy-and-load-
balancing-concepts
•https://signalvnoise.com/posts/1073-nuts-bolts-haproxy
•http://blog.kloud.com.au/2013/07/04/elbs-do-not-cater-for-your-environment-set-up-haproxy-
for-your-iis-servers-2/
•http://blog.stackoverflow.com/2010/01/stack-overflow-network-configuration/
•http://mervine.net/comparing-load-balancing
•https://serversforhackers.com/haproxy/

17. Thank you