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IBM eNetwork Communications Server for Windows NT
Host Publisher Feature, Version 6.01
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Host Publisher Hints and Tips

High Traffic Web Sites

You can use a variety of techniques to handle high traffic levels on your web site with Host Publisher.

The general procedure should be:

  1. Estimate the amount of traffic your web site will handle at peak load.

  2. Measure the performance of each component, using your hardware, your network, and your data sources.

    Some components to consider are your web server, your network, your page server, and whatever data sources your Page Server is using.

  3. Identify components that will need to be replicated or to have their performance improved to meet your traffic requirements.

  4. Plan and implement the necessary changes.

  5. Measure performance. Repeat until your performance goals are met.
Most of this work is not specific to Host Publisher. We will only go into details about Host Publisher.

Standard web techniques

Host Publisher uses standard web servers and can accept requests from multiple web servers. Therefore, you can use industry-standard techniques for improving your web server performance, including tuning, caching, better hardware (computer and network), and load-spreading products.

Page Server

There are a number of techniques that can be used to improve the performance of a Page Server.

Hardware

The most important hardware component in a server machine is memory. Memory is relatively inexpensive, especially when you consider how much and how easily more memory can improve your server performance. Consider 128M of memory to be the minimum for a modern server machine, and add more memory freely as long as more memory continues to improve performance.

Page Caching

The easiest way to improve page server performance is to turn on page caching for all web pages that do not require instantaneously updated data. Even if the cache timeout is only ten minutes, if a hundred requests for the page occur each hour, 94 of them will be satisfied from the cache instead of generating the web page again.

Caching will increase use of memory and disk space, and disk traffic.

Java memory

Increasing the amount of memory available to Java can improve the performance of Java-intensive SIMs, such as the Host Access SIM.

By default, Host Publisher gives Java 16M of memory. If you have a lot of memory available, and you are using the Host Access SIM, increasing this value can allow you to process more requests simultaneously.

If Host Access page requests are failing with error messages indicating lack of Java memory, you must increase this value or decrease the number of Page Server threads.

Create a new registry entry under

HKEY_LOCAL_MACHINE\SOFTWARE\IBM\Host Publisher\Config
called JVMHeapSize. The entry should be a DWORD. Its value is the Java memory size in megabytes. The default, if there is no registry entry, is 16M.

Host Access performance

If you are using the Host Access SIM, consider setting pages to client scope or using connection caching to improve performance if appropriate.

Threads

The number of Page Server threads affects the Page Server's performance, but not always in a straightforward way.

For example, if it takes 1 second to process a request, and the Page Server has 5 threads, the Page Server's maximum rate will be 5 requests per second.

If you increase the number of threads to 10, the Page Server might process 10 requests per second. But if the requests are CPU or memory-intensive, processing 10 at the same time may slow down the Page Server so it takes 3 seconds to process each request. The rate will only be 3.3 requests per second, worse than before.

It is important to test Page Server performance after adjusting the number of threads. Too many threads can be as bad as too few.

More threads require more memory and CPU, and can increase disk and network traffic.

Interaction of changes

These factors are all related. For example, after adding memory or moving to a faster CPU, the Page Server might be able to run with more threads. After changing any factor, reconsider the others.

One approach would be to install the fastest processor and the most memory you can afford (focusing most on memory), turn on page caching, and then use experimentation to determine the optimum number of threads.

Traffic mix

If your site will serve some simple requests and some complicated (and expensive) requests, consider assigning them to different Page Servers. It is easier to plan your Page Server performance if its work load is homogeneous.

Replication of Page Servers

Adding more Page Servers is an easy way to process requests faster. If the Page Servers are using external data sources, consider their ability to handle the load. You might need to replicate the data sources or improve their performance in order to handle the increased number of Page Servers.

Failure

A high-traffic site should plan for failure. Even if hardware and networks never fail, machines must be stopped sometimes for maintenance.

Provide a backup Dispatcher.

Ensure that all Web libraries are available on at least two Page Servers, so that no single Page Server failure can stop access to your data.

Ensure that if any Page Server fails, the remaining Page Servers with the same Web libraries have sufficient extra capacity to handle the failed Page Server's load.

If you use a single Web server, keep a hot backup ready.

If possible, plan for your backup Dispatcher and Page Servers to remain accessible even if your primary network fails.


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IBM eNetwork Communications Server for Windows NT
Host Publisher Feature, Version 6.01