Suggestions and Recipes for Log Analysis

Please add your tips and tricks to this page. Extraction scripts and Excel Macros etc welcome!

Generating Appropriate JMeter Logs

The default data logged during JMeter testing is quite sparse - important request and response fields are stored, but the full response sent back by the server is not stored. This is done to avoid bogging down the test client during load testing.

Using the following JMeter parameters on the command line generates log entries with corresponding higher detail for the test run.

-Jjmeter.save.saveservice.data_type=true -Jjmeter.save.saveservice.label=true  -Jjmeter.save.saveservice.response_code=true -Jjmeter.save.saveservice.response_data=true -Jjmeter.save.saveservice.response_message=true -Jjmeter.save.saveservice.successful=true -Jjmeter.save.saveservice.thread_name=true  -Jjmeter.save.saveservice.time=true"

The JMeter timestamp_format parameter can be used to specify logentry timestamps format. For eg:

-Jjmeter.save.saveservice.timestamp_format="yyyy-MM-dd HH:mm:ss"

As of April 2006, JMeter 2.1.1 must also be run with the following flag to ensure logfile uniformity:

-Dfile_format.testlog=2.0

This forces JMeter to use the old logformat which generates <sampleResult> element for all log entries. The newer format instead generates <httpSample> elements for HTTP requests and <sampleResult> for JDBC sampler entries - this is inconvenient from a automated log processing point of view. Refer this [http://mail-archives.apache.org/mod_mbox/jakarta-jmeter-user/200604.mbox/%3cE5D178BFB0356B48A48B8330B2903721ED5CA6@syd1exc04.CE.CORP%3e Jmeter-user thread] for more details

The above settings can also be defined as global properties in the JMeter.properties configuration file.

The JMeter Log Format

The format of JMeter log entries generated when using the flags in the previous section is defined in the table below. (Editing note: 4 spaces are used to denote one level of XML 'indentation'.)

    @version    	

    /sampleResult/...

        @timeStamp	

        @dataType	

        @threadName	

        @label		

        @time		

        @responseMessage	

        @responseCode	

        @success		

        /sampleResult/...	

        /property		

            @xml:space	

            @name		

        /assertionResult/...	

            @failureMessage	

            @error		

            @failure		

        /binary		

Perl Based Method for Log Extraction

Here are some steps to import and process JMeter log data in Excel. Steps #3 and 4 are painstaking and can be automated by Excel macros - however, this is beyond my abilities at the moment:

1. First, generate delimited file for import into Excel.
   

I use Perl to parse the XML logs and generate a delimited file for import into Excel. The heart of the Perl script is the regular expression below. Each line in the JMeter logfile must be matched to this expression:

# Regular expression extracts relevant fields from the log entry. 
/timeStamp="(\d+)".+?threadName="(.*?)".+?label="(.+?)" time="(\d+?)".+?success="(.+?)"/;

# Data in the regex variables is accessed for use in building suitably-delimited line
my $timestamp = $1; # unix timestamp 
my $threadname = $2; # thread label
my $label = $3; # operation label 
my $time = $4; # operation time in milliseconds
my $success = $5; # boolean success indicator for this operation

The complexity of the regular expression is required to parse nested log entries that occur during HTTP redirects. A normal log entry line logs one HTTP 'sampler' operation. For eg:

<sampleResult ... time="156" ... />

However, when the opertion had a HTTP redirect (HTTP status code 302), JMeter records the redirects as nested <sampleResult> elements – these which still occur on the same line as the log entry:
{{{<sampleResult ... time="2750"> <sampleResult ... time="2468" ... /> <sampleResult time="141" .../> <sampleResult ... time="141" .../> </sampleResult>
}}}

The outermost <sampleResult> element has time = 2750 milliseconds. This is the sum of times of the nested redirect elements. We are only interested in the data contained in the outermost element. Hence the regular expression uses the non-greedy pattern match operator ( .*? or .+?) to ignore the latter <sampleResult> elements.

On the other hand, Excel 2002 can directly import JMeter XML format logs. However, it has problems with entries for HTTP 302 redirects. The nested log entry example above will generate three rows in Excel, with the total time repeated thrice. i.e:

Login	2750
Login	2750
Login	2750 

2. Convert Timestamps to Excel Format

Once the data is in Excel, I convert the timestamp column from Jmeter's Unix timestamp format (base year 1970) to the Excel format (base year 1900) using this following formula. This formula is applied to the entire timestamp column. (NOTE: a better formula was mentioned on JMeter users list sometime back)

=(x/1000+((365*70+17)*86400))/86400

3. Now sort rows on the operation name (i.e. JMeter sampler name)

4. Generate suitable reports and graphs manually.

For instance, one can generate a graph of page load times v/s time for different operations (e.g.: login, add 1 line to the order, etc). A different series in the graph is needed for each operation type used - this can be quite painstaking to add to a graph when there is a lot of data.

The graphs generated can be quite useful in visualizing performance of websites. See the graph below for an example of one such dummy website. The JMeter test that generated the data imposed a steady "normal load" component, but also imposed two short-term, high volume "surge loads" spread 10 minutes apart. (This was done using a separate JMeter thread group).

attachment:DummyWebsitePerformance.JPG

XSL script to extract Jmeter logs

(Peter Thomas) There are XSL scripts that I found that come along with the Jmeter distribution in the "extras" folder as "jmeter-results-report.xsl" and "jmeter-results-detail-report.xsl". However the HTML rendered is very complex, doesn't work well in Firefox and is bit difficult to grab into Excel.

Here's a simple script that just converts the Jmeter XML into an HTML table and does nothing else. You can do a "select all" on the HTML, and paste into Excel and it works smoothly.

The advantage of the XSL approach is the handling of the nested "sampleResult" elements if they are encountered. In the script below they are ignored. You can uncomment the XML comment that appears toward the end of the script and pick up the nested "sampleResult"s if you want but they really get in the way. The primary level "sampleResult" elements contain the sum of nested "sampleResult" times so this should be OK.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output method="html" indent="yes" encoding="US-ASCII" doctype-public="-//W3C//DTD HTML 4.01 Transitional//EN" />

<xsl:template match="/">
  <html>   
    <body>
       <xsl:apply-templates/>
    </body>
  </html>
</xsl:template>

<xsl:template match="testResults">
  <table border="1">
    <tr>
      <th>timeStamp</th>
      <th>dataType</th>
      <th>threadName</th>
      <th>label</th>
      <th>time</th>
      <th>responseMessage</th>
      <th>responseCode</th>
      <th>success</th>
    </tr>    
    <xsl:apply-templates/>
  </table>
</xsl:template>


<xsl:template match="sampleResult">		
  <tr>
    <td><xsl:value-of select="@timeStamp"/></td>
    <td><xsl:value-of select="@dataType"/></td>
    <td><xsl:value-of select="@threadName"/></td>
    <td><xsl:value-of select="@label"/></td>
    <td><xsl:value-of select="@time"/></td>
    <td><xsl:value-of select="@responseMessage"/></td>
    <td><xsl:value-of select="@responseCode"/></td>
    <td><xsl:value-of select="@success"/></td>
  </tr>
  <!--<xsl:apply-templates/>-->
</xsl:template>
    
</xsl:stylesheet>

It should be easy to apply this XSL stylesheet on your Jmeter file. I use a small Java program. I think you can add an xsl stylesheet processing instruction at the start of your XML file and open it in IE or Firefox directly. Someone can post on how to exactly do this.

Once within Excel, pivot tables are the way to go.

5. You can also use the following package that mixes Excel Macro, java transformation and xsl transformation of the .jtl files. It automaticaly generates Excel graphs using a Macro. The package is available here :
attachment:scripts_jmeter.zip