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<!DOCTYPE document[
<!ENTITY sect-num '17'>
<document prev="best-practices.html" next="component_reference.html" id="$Id: boss.xml 1175606 2011-09-25 22:28:22Z sebb $">
<author email="">Martin Ramshaw</author>
<title>User's Manual: My boss wants me to...</title>
<section name="&sect-num;. Help! My boss wants me to load test our web app!" anchor="boss">
<p>This is a fairly open-ended proposition. There are a number of questions to
be asked first, and additionally a number of resources that will be needed. You
will need some hardware to run the benchmarks/load-tests from. A number of
tools will prove useful. There are a number of products to consider. And finally,
why is Java a good choice to implement a load-testing/Benchmarking product.
<subsection name="&sect-num;.1 Questions to ask" anchor="questions">
<p>What is our anticipated average number of users (normal load) ?
<p>What is our anticipated peak number of users ?
<p>When is a good time to load-test our application (i.e. off-hours or week-ends),
bearing in mind that this may very well crash one or more of our servers ?
<p>Does our application have state ? If so, how does our application manage it
(cookies, session-rewriting, or some other method) ?
<p>What is the testing intended to achieve?</p>
<subsection name="&sect-num;.2 Resources" anchor="resources">
<p>The following resources will prove very helpful. Bear in mind that if you
cannot locate these resources, <b>you</b> will become these resources. As you
already have your work cut out for you, it is worth knowing who the following
people are, so that you can ask them for help if you need it.
<subsection name="&sect-num;.2.1 Network" anchor="network">
<p>Who knows our network topology ? If you run into any firewall or
proxy issues, this will become very important. As well, a private
testing network (which will therefore have very low network latency)
would be a very nice thing. Knowing who can set one up for you
(if you feel that this is necessary) will be very useful. If the
application doesn't scale as expected, who can add additional
hardware ?
<subsection name="&sect-num;.2.2 Application" anchor="application">
<p>Who knows how our application functions ? The normal sequence is
<li>test (low-volume - can we benchmark our application?)</li>
<li>benchmark (the average number of users)</li>
<li>load-test (the maximum number of users)</li>
<li>test destructively (what is our hard limit?)</li>
The <b>test</b> process may progress from black-box testing to
white-box testing (the difference is that the first requires
no knowledge of the application [it is treated as a "black box"]
while the second requires some knowledge of the application).
It is not uncommon to discover problems with the application
during this process, so be prepared to defend your work.
<subsection name="&sect-num;.3 What platform should I use to run the benchmarks/load-tests ?" anchor="platform">
<p>This should be a widely-used piece of hardware, with a standard
(i.e. vanilla) software installation. Remember, if you publish your results,
the first thing your clients will do is hire a graduate student to verify them.
You might as well make it as easy for this person as you possibly can.
<p>For Windows, Windows XP Professional should be a minimum (the others
do not multi-thread past 50-60 connections, and you probably anticipate
more users than that).
<p>Good free platforms include the linuxes, the BSDs, and Solaris Intel. If
you have a little more money, there are commercial linuxes.
This may be worth it if you need the support.
For non-Windows platforms, investigate "ulimit -n unlimited" with a view to
including it in your user account startup scripts (.bashrc or .cshrc scripts
for the testing account).
<p>As you progress to larger-scale benchmarks/load-tests, this platform
will become the limiting factor. So it's worth using the best hardware and
software that you have available. Remember to include the hardware/software
configuration in your published benchmarks.
<p>Don't forget JMeter batch mode. This can be useful if you have a powerful server
that supports Java but perhaps does not have a fast graphics implementation,
or where you need to login remotely.
Batch (non-GUI) mode can reduce the network traffic compared with using a remote display or client-server mode.
The batch log file can then be loaded into JMeter on a workstation for analysis, or you can
use CSV output and import the data into a spreadsheet.</p>
<subsection name="&sect-num;.4 Tools" anchor="tools">
<p>The following tools will all prove useful. It is definitely worthwhile to
become familiar with them. This should include trying them out, and reading the
appropriate documentation (man-pages, info-files, application --help messages,
and any supplied documentation).
<subsection name="&sect-num;.4.1 ping" anchor="ping">
This can be used to establish whether or not you can reach your
target site. Options can be specified so that 'ping' provides the
same type of route reporting as 'traceroute'.
<subsection name="&sect-num;.4.2 nslookup/dig" anchor="dig">
While the <u>user</u> will normally use a human-readable internet
address, <u>you</u> may wish to avoid the overhead of DNS lookups when
performing benchmarking/load-testing. These can be used to determine
the unique address (dotted quad) of your target site.
<subsection name="&sect-num;.4.3 traceroute" anchor="traceroute">
If you cannot "ping" your target site, this may be used to determine
the problem (possibly a firewall or a proxy). It can also be used
to estimate the overall network latency (running locally should give
the lowest possible network latency - remember that your users will
be running over a possibly busy internet). Generally, the fewer hops
the better.
<subsection name="&sect-num;.5 What other products are there ?" anchor="products">
<p>There are a number of commercial products, which generally have fairly
hefty pricetags. If you can justify it, these are probably the way to go.
If, however, these products do not do exactly what you want, or you are on a
limited budget, the following are worth a look. In fact, you should probably
start by trying the Apache <b>ab</b> tool, as it may very well do the job
if your requirements are not particularly complicated.
<subsection name="&sect-num;.5.1 Apache 'ab' tool" anchor="ab">
You should definitely start with this one. It handles HTTP 'get' requests
very well, and can be made to handle HTTP 'post' requests with a little
effort. Written in 'C', it performs very well, and offers good (if basic)
performance reporting.
<subsection name="&sect-num;.5.2 HttpUnit" anchor="httpunit">
This is worth a look. It is a library (and therefore of more interest to
developers) that can be used to perform HTTP tests/benchmarks. It is
intended to be used instead of a web browser (therefore no GUI) in
conjunction with <b>JUnit</b>.
<subsection name="&sect-num;.5.3 Microsoft WAS" anchor="WAS">
This is definitely worth a look. It has an excellent user interface
but it may not do exactly what you want. If this is the case, be aware
that the functionality of this product is not likely to change.
<subsection name="&sect-num;.5.4 JMeter" anchor="JMeter">
If you have non-standard requirements, then this solution offers an
open-source community to provide them (of course, if you are reading
<u>this</u>, you are probably already committed to this one). This
product is free to evolve along with your requirements.
<subsection name="&sect-num;.6 Why Java ?" anchor="java">
<p>Why not Perl or C ?
<p>Well, Perl might be a very good choice except that the Benchmark package
seems to give fairly fuzzy results. Also, simulating multiple users with
Perl is a tricky proposition (multiple connections can be simulated by forking
many processes from a shell script, but these will not be threads, they will
be processes). However, the Perl community is very large. If you find that
someone has already written something that seems useful, this could be a very
good solution.
<p>C, of course, is a very good choice (check out the Apache <b>ab</b> tool).
But be prepared to write all of the custom networking, threading, and state
management code that you will need to benchmark your application.
<p>Java gives you (for free) the custom networking, threading, and state
management code that you will need to benchmark your application. Java is
aware of HTTP, FTP, and HTTPS - as well as RMI, IIOP, and JDBC (not to mention
cookies, URL-encoding, and URL-rewriting). In addition Java gives you automatic
garbage-collection, and byte-code level security.
<p>And once Microsoft moves to a CLR (common language run-time) a Windows Java
solution will not be any slower than any other type of solution on the Windows
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