5 More Discussions You Might Find Interesting
1. Linux
Hello Guys,
Hope you all doing well . :)
I was checking load balance command (uptime)on VM server and got below output.
# uptime
07:08:40 up 52 min, 2 users,a load average: 0.45, 0.11, 0.03
A :How we can calculate load average?
Thank you in advance !!
Cheers:)
Dont forget... (1 Reply)
Discussion started by: Nats
1 Replies
2. UNIX for Advanced & Expert Users
we use piranha load balancer with two nodes
even the primary node is running fine and up failover happend to secondary node
this happend quite few times ehy node2 cannot talk to node1
what logs are to be checked and investigate why failover occured
pulse: partner dead: activating... (0 Replies)
Discussion started by: robo
0 Replies
3. Red Hat
Hi,
What's the best load balancer for Linux (CentOS, SuSE) according to your personal experience?
Linux Virtual Server (LVS) is a famous one, but their download site has not been updated since 2007. Their web and mailing list are so quiet. Is the Ultra Monkey project including LVS... (1 Reply)
Discussion started by: aixlover
1 Replies
4. AIX
Hi All,
How do I failover on the ip load balancer (back and forth)? It involves first to load a new config on the passive ip. If success, load the new config on the ip active (which is now passive).
Any idea, please.
Thanks in advance. (0 Replies)
Discussion started by: itik
0 Replies
5. Programming
Halo mates,
I m going to write a load balancer with C. Does anybody know some good reference on this?
Cheers,
Elton (5 Replies)
Discussion started by: EltonSky
5 Replies
LEARN ABOUT DEBIAN
perlbal::manual::loadbalancer
Perlbal::Manual::LoadBalancer(3pm) User Contributed Perl Documentation Perlbal::Manual::LoadBalancer(3pm)
NAME
Perlbal::Manual::LoadBalancer - Using Perlbal as a Load Balancer
VERSION
Perlbal 1.78.
DESCRIPTION
How to configure a Perlbal Load Balancing service.
READ ME FIRST
Please read Perlbal::Manual::Configuration first for a better explanation on how to configure Perlbal. This document will make much more
sense after reading that.
Using Perlbal as a Load Balancer
For a better understanding of how to set up Perbal as a Load Balancer, it should be noted that a Load Balancer and a Reverse Proxy can
often be the same thing; not always, but often.
A Load Balancer is a server (or device) that balances requests across a number of servers to spread the load. A Reverse Proxy can still do
this but also have a number of other features.
Perlbal as a Reverse Proxy provides features such as buffering content, preserving connections to the backend servers, starting connections
ahead of time and a high priority queue, among others.
You could almost say that a Load Balancer is a subset of a Reverse Proxy (it's not, but you could).
When it comes to Perlbal, the Load Balancer is implemented as a Reverse Proxy without all the extra options, and that's why you set the
role of a Load Balancer to "reverse_proxy":
SET role = reverse_proxy
Simple load balancing
Let's assume you want to configure two machines to serve your website and you want to let Perlbal decide how to balance the requests. For
the sake of this exercise let's assume you have two servers at:
10.0.0.1:80
10.0.0.2:80
And now you want to use these two machines to serve your website at:
10.0.0.3:80
Here's a sample configuration to make this happen:
CREATE POOL mywebsite
POOL mywebsite ADD 10.0.0.1:80
POOL mywebsite ADD 10.0.0.2:80
CREATE SERVICE service_mywebsite
SET role = reverse_proxy
SET pool = mywebsite
SET listen = 10.0.0.3:80
ENABLE service_mywebsite
The first line defines a pool of machines called "mywebsite". The second and third lines add your two machines to that pool (note that the
indentation is not mandatory).
After that you define a service called "service_mywebsite" with the role "reverse_proxy" set to listen on "10.0.0.3:80" and using the pool
"mywebsite" to serve the requests.
The last line is what allows you have several services configured in a file even if they are not currently active (a common scenario is to
configure everything on the file and then enable/disable services on-the-fly as required; see Perlbal::Manual::Management for more
information on this process).
The Load Balancing algorithm
Perlbal uses a highly efficient load balancing algorithm. It is very effective for distributing dynamic web requests among potentially
heterogeneous hardware.
First, backend servers must have their MaxClients (for apache, or equivalent) setting tuned to a reasonable limit. If your hardware can run
20 requests in parallel before running out of CPU, set MaxClients to 20.
Next, by default Perlbal will distribute requests randomly. Opening a new connection to any available backend, and issuing the request.
The proper algorithm is able to be used if "verify_backend", "backend_persist", "backend_persist_cache", and "connect_ahead" are enabled.
SET persist_backend = on
SET verify_backend = on
SET backend_persist_cache = 5
SET connect_ahead = 2
In this configuration, Perlbal will only route client requests to backends that it knows are real processes, instead of the OS listen
queue. It will attempt to reuse pre-verified backends, and will attempt to create slightly more idle connections than it needs in
preparation of future requests.
When you put all this together, it becomes less likely that a client will wait for Perlbal to find an available backend. By setting your
MaxClients properly, backends are able to serve traffic without getting overwhelmed. If no backends are available, Perlbal will queue them
internally, rather than overload backends.
You would want to disable "verify_backend" if you are balancing across image servers, or other extremely lightweight requests.
SEE ALSO
Perlbal::Manual::Configuration, Perlbal::Manual::FailOver, Perlbal::Manual::Management, Perlbal::Manual::ReverseProxy.
perl v5.14.2 2011-01-23 Perlbal::Manual::LoadBalancer(3pm)