javaweb-applicationsjmeterload-testingblazemeter

JMeter slow with "Retrieve all embedded resources" - how do I scale?

TLDR:

More details:

I'm recording the jmx script using the BlazeMeter Chrome extension. The user logs in, and completes a course and a test. There are many ajax requests being made along the way. Around 350 - 400 steps for the script. Mostly ajax POST request that have a json response.

When I click through manually in Chrome, the site loads quickly. Maybe a page load takes 2 seconds tops.

But when I import that script into JMeter with the "Retrieve all embedded resources" and "Parallel downloads" set to 6, and run it (in the GUI initially with just 1 user), it will get through, say, 7 steps quickly, and then just hang, sometimes for 10+ minutes before advancing to the next step. This doesn't happen if I uncheck "Retrieve all embedded resources", but I don't want to do that since that wouldn't be a realistic test.

If I take that same test and run it with 100 users (from the command line using JVM_ARGS='-Xms4096m -Xmx4096m' sh jmeter -n -t myfolder/mytest.jmx -l myfolder/testresults.jtl), I get Uncaught Exception java.lang.OutOfMemoryError: Java heap space in thread Thread and my computer fan goes nuts.

I have an HTTP Cache Manager configured with only "Use Cache-Control/Expires header when processing GET requests" checked and I've lowered the "Max Number of elements in cache down to 10 since that's the only way I can get the test running at all.

Ideally, I'd like to test thousands of users at once, but if I can't reliably get 100 users tested, I don't understand how I'm supposed to scale to thousands.

I see that there are other cloud-based testing options, and I've tried a few out now, however I always come to a halt when it comes to configuring how to test logged in users. Seems like most solutions don't support this.

Feels like the kind of thing that lots of people should have come across in the past, but I find almost no one having these issues. What's the right way to load test thousands of logged-in users on a web application?

Solution

    1. If JMeter "hangs" for 10 minutes retrieving an embedded resource there is a problem with this specific resource, you can see the response times for each resource using i.e. View Results Tree listener and either raise a bug for this particular "slow" component or exclude it from the scope using HTTP Request Defaults. There you can also specify the timeout, if the request won't return the response within the given timeframe - it will be marked as failed so you won't have to wait for 10 minutes:

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    2. Your way of increasing the heap is correct, it looks like 4Gb is not sufficient you will either have to provide more or consider switching to distributed testing

    3. Make sure to follow JMeter Best Practices in any case. If your "computer fan goes nuts" it means that CPU usage is very high therefore JMeter most probably won't be able to send requests fast enough so you will get false-negative results.