Step by Step Trouble Shooting

Performance SOP

Identify the Bottleneck

Usually the bottleneck can be found in one of these areas:

• client
• network
• server

To breakdown a slow performing web application is a good idea to start, where the bad performance is perceived... in the browser. Most modern browsers provide very sophisticated tools to start the search for the bottleneck and draw some conclusions, and exclude other possible causes easily.

Dev tools (Network)

Chrome -> [F12]

Firefox -> [F12] or Firebug

IE9+ -> [F12]

IE8 -> fiddler2

Investigating the network traffic following the questions below the biggest problem area(s) should become apparent after a few minutes:

1. Are there one or more long running requests?

NO → #Client Side Issue

YES

↓

2. Is it a static resource?

YES (js, css, images...) → check #ZK Server Configuration (debug / cache / compression) → STILL SLOW → #Network Issue

NO (dynamic request into ZK application)

• *.zul = full page request (can be followed by ajax requests)
• zkau/* = ajax request

↓

3. Which PHASE of the request is slowest ? (examples based on Chrome developer tools)

CONNECTING (or one of Proxy, DNS Lookup, Blocking, SSL)

3.a) Is this a network problem (everything between browser and ZK Application)?

• test ping / trace route to different servers
• test dns lookup timing

YES → #Network Issue

NO → #Server Side Issue (application takes long time to accept connection, or even times out)

SENDING

3.b) Is the request unreasonably big?

YES → #Client Side Issue

NO

↓

3.c) Is the bandwidth low?

• e.g. try upload the same amount of data to the server via ftp/scp to check possible upload speed

YES → #Network Issue

NO → #Server Side Issue (application server receiving request data slowly)

WAITING → #Server Side Issue (application server taking long time to prepare response)

RECEIVING

3.d) Is the response unreasonably big?

YES → #ZK Server Configuration (render on demand / compression)

NO

↓

3.e) Is the bandwidth low?

• e.g.try to download the same amount of data from the server via ftp/scp to check download speed

YES → ask your administrator to fix it ;)

NO → #Server Side Issue (appserver sending response data slowly)

Server Side Issue

ZK Server Configuration

• check debug mode → zk config should not be enabled (disabled by default)
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/zk.xml/The_client-config_Element/The_debug-js_Element

• check caching config → should not be disabled (enabled by default)
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/zk.xml/The_Library_Properties/org.zkoss.web.classWebResource.cache
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/zk.xml/The_Library_Properties/org.zkoss.zk.WPD.cache
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/zk.xml/The_Library_Properties/org.zkoss.zk.WCS.cache

• check compression settings → should not be disabled (enabled by default)
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/web.xml/ZK_AU_Engine#The_Initial_Parameters
  • http://books.zkoss.org/wiki/ZK_Configuration_Reference/web.xml/ZK_Loader#The_Initial_Parameters

• check render on demand settings
  • http://books.zkoss.org/wiki/ZK_Developer%27s_Reference/Performance_Tips/Client_Render_on_Demand
  • TODO more ROD settings, fetch size...

• TODO ??? maybe more tweaks ???

Network Issue

If something in your infrastrucure (routers, proxies, web servers...) is causing the performance issues, there is little you can do as web application developer. So these topics are not part of this SOP

→ Please ask your network administrator to identify/exclude infrastructure problems.