On 29.10.2004, at 19:08, Peter Lin wrote:
if you're looking for better client performance I would explore other areas first.
1. use gzip compression - this can reduce the html to 1/10th the size. your mileage will vary.
This is being looked at - loadbalancer vrs tomcat
2. caching results on the web-tier
Very dynamic content
3. putting the images on a dedicated image server
Already being done. 2x Servers running apache - which also have this keep-alive problem. Running 1000 threads per server is NOT my idea of a good time. I will be having a look at a couple of other alternatives to apache over the next couple of weeks. Due to operating system/ kenerl overheads
time for one request <> (time for 10 parallel requests)/10 <> (time for 1000 parallel requests)/1000
Squid is a good example of how you can server MANY connections without starting thousands of threads.
4. distributing your servers across multiple ISP. many service providers don't tell you this, but often their pipe is saturated and can't really handle a large number of concurrent requests. if you host your own servers i would recommend getting more than 1 connection and use different providers
This is NOT a pipe saturation issue. The issue is definitely a tomcat/ number of connections issue.
I already have this problem in my local network with load tests.
Most browsers today are Http1.1 compliant, which means they are limited to 2 connections to the same server. Normally the browser will use the same connection to get the html and the other resources like images and javascript.
This will only happen if keep-alives are enabled. If keep-alives are disabled each GET will be a new connection. The F5 load balancers (4.5) have a 'cool-feature?!' that 'forwards' the keep-alive connection through to the backend server - With the 4.5 version of the software they are doing packet mangling. This means that even though the cllient only has 2 connections, the load balancer multiplies this connection to EACH of the backend servers with which the client is communicating, ie: static servers get 2 connections per client, statistic servers get 2 connections per client, tomcats get 2 connections per client..
Version 9 of the software has just come out, and it does proxying this should hopefully help solve this problem - I am still in the process of testing the new version.
Andrew
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