WebLoad 4.1.3 README

Linas Vepstas (linas@linas.org)

WebLoad is a collection of tools for testing and measuring web applications and web servers. The tools can be used to record and playback HTTP conversations between a web browser and a web server, make timing measurements, and gather statistics. The true power of this tool lies in its stress-test and stress-measurement abilities: It can simulate a large number of users accessing a web site in structured yet randomized sessions.

WebLoad has been loosely derived from the public-domain WebStone package, but has seen a major redesign since then, with the addition numerous features and enhancements. Features include:

• Record and playback of URL's, including ...
  • Ability to handle generic HTTP traffic, including XML-based prototocls such as OFX. Custom HTTP headers and bodies may be specified.
  • Ability to trace/record through multiple servers, capturing entire web surfing sessions over many sites.
  • Can act as man-in-the-middle, gathering detailed traces of HTTP traffic to debug server, browser or proxy bugs.
  • Checksum generation and validation to detect mangled, missing or misdelivered pages.
  • Adjustable timeout to detect non-responding servers.
  • Logon password support, allowing websites that require customer registration and logon to be traced.
  • Autologoff when error condition is detected, allowing a logon id to be reused, thus avoiding a manual reset or logon timeout.
  • Support for cookies and handles embedded in URL's.
  • Limited ability to make generic text and key-value substitutions in HTTP header and body.
  • Support for HTTP/1.0 and HTTP/1.1 protocols, including KeepAlive and persistant connections.
  • Support for SSLv2 and SSLv3 encryption.
  • Works through Socks & Proxy firewalls.
  • Rudimentary support for JavaScript, Frames, Layers, base href tags. This allows more complex sites to be correctly traversed.
  • Automatic followup of redirects (302 and 304 return codes).
  • Works with password-protected sites.

• Ability to emulate a real user through a variety of features, such as ...
  • Emulation of the browser image (GIF) cache; cached images, and audio/video clips are not refetched.
  • Fixed or randomly distributed "think time" to simulate a user pausing to read a web page. Think time may be assigned per page, or an average declared for the session. Exponential and gaussian distributions supported.
  • Blocks of URL's can be assigned fractional probabilities for playback. Thus, complex user behaviours, such as visting only part of a web site only some of the time can be emulated.

• Ability to gather timestamps and performance statistics, including ...
  • Ability to time individual events, as well as gether summary statistics for entire sessions. Features include:
  • Ability to timestamp a user session, including socket connect, SSL negotiation, socket read and write times, elapsed delay times. Timestamps can be obtained during record and during playback.
  • Automatic collection of statistics, including average, min, max and standard deviations.
  • Stats may be reported in detail, in blocks, and as a summary. For example, the standard deviation for socket connection delay for a particular URL can be obtained, or the average connect time for a block of URL's, or the average end-to-end time over all pages for the entire session.

• Ability to stress load a server and gather stress statistics through multi-user emulation. Features include ...
  • Load Rampup. Startup of clients staggered in blocks, avoiding initialization bottlenecks, as well as lockstep servicing, "sloshing" and other mutli-user measurement pitfalls.
  • Statistics gathering synchronization. This guarentees that that no statistics are gathered during the rampup and rampdown phases.
  • Statistics gathering checkpointing. Statistics are gathered and presented only for whole sessions, thus excluding partially begun or paritally completed sessions that occur at rampup and rampdown. Stats are "rolled back" to last complete session.
  • Variety of scripts to extract, summarize and manipulate multi-user run reports, including CPU usage, queue lengths, page and session times.

• Multi-OS support: AIX, Linux, 95 and NT.
  • Ports to other Unixes should be straightforward.
  • Multiuser support, stress-loading and tools not available on 95/NT due to OS limitations. (Multiuser support requires shared memory. Timeouts require alarms, neither are supported on NT/95. SSL support requires encryption, NT licensing is restrictive/prohibitive. NT/95 TCP/IP stack is slowww, shaky and prone to frequent hangs, crashes.)