I'd few ques on technical details of JMeter mostly pertaining to distributed setup vs independent JMeter engines (since JMeter controller can become a bottleneck in case of several JMeter load generators). Would be great if anybody can help with the understanding here -
How is JMeter distributed setup orchestrated by JMeter controller (i.e. called master or client)? Can we use the same logic to synchronize test among independent JMeter engines (independent mode)?
Is there a way to pool connections across vUsers?
Function of ASYNC_QUEUE in backend listener and it's expected side-effects in independent mode (mentioned above), what happens when queue is full?
Does/Is there a way for JMeter to execute javascript/act as headless browser?
How does DNS resolution happen for JMeter? Does it resolve for each vuser?
Your "question" looks like a compilation of interview questions rather than something connected with your single current concern and I don't think it's a proper place/way to ask it, I believe it should be: one post - one question.
Whatever
How is JMeter distributed setup orchestrated by JMeter controller - JMeter master sends .jmx script to slaves and collects results from them. Theoretically you can implement your own mechanism for delivering the test plan and eventual dependencies to the individual JMeter engines and running the test at the same time. Then you will need to collect the .jtl results files from the engines and combine it into a single one.
Is there a way to pool connections across vUsers? - JMeter does it internally
When the queue is full no more new sample results will be taken for processing by the backend listener so the results won't be "realtime" anymore, you will see the new results as free slots will be appearing in the queue
For JMeter per-se - no, AJAX calls can be simulated using Parallel Controller, for client-side performance testing, JavaScript execution profiling and rendering speed measurement you will need to use a read browser, no matter normal or headless, there is WebDriver Sampler plugin providing JMeter integration with Selenium
DNS resolution is dependent on underlying OS and/or JVM DNS resolution implementation, there is DNS Cache Manager which enables overriding hosts entries and using custom DNS resolver so each thread looks up the IP address on its own
Related
I am new to performance testing. I have a task on measuring the web application performance. I need to find out which modules/calls are causing deadlock, timeout and memory issues.
Q1. How can I use JMeter to find out deadlock, memory and timeout issues? If I do the following steps, it is the right way to trace those issues?
create a test plan in JMeter, which contains multiple Thread Group.
In each thread group, it contains multiple HTTP requests and 200 or
more users plus infinite loop.
Monitor JMeter results and SQL
profiler for deadlock.
Q2. JMeter is the right tool for tracking those issues? Or, should I use browser based performance testing tool such as LoadNinja, LoadView?
Thanks
Bonnie
Q1 JMeter per se doesn't provide any toolchain to detect deadlock and memory issues, the HTTP Request sampler (or even better HTTP Request Defaults) provides possibility to set the timeouts, if the value is blank - it will default to operating system timeout or web server timeout, whatever comes the first
If you conduct some form of stress test, i.e. start with 1 virtual user and gradually increase the load at some point you will see that response time starts growing and number of requests per second starts decreasing. So it's the point of maximum system performance and after that the performance will be degrading.
To monitor application under test memory you can use JMeter PerfMon Plugin, it will allow you to state whether the lack of RAM is the cause of the performance issue
With regards to deadlocks, it should result in HTTP Request sampler failure (or timeout), JMeter won't give you the underlying reason, but it will give you the timestamp and you should be able to check what happened with your application/database at that moment.
Q2 well-behaved JMeter test must produce the same network footprint as a real browser, if your test plan is good enough the system under test shouldn't be able to distinguish whether it's being hit by JMeter or by a real user using the real browser. JMeter will not give you client-side performance metrics like page rendering time or JavaScript execution time as:
JMeter is not a browser, it works at protocol level. As far as web-services and remote services are concerned, JMeter looks like a browser (or rather, multiple browsers); however JMeter does not perform all the actions supported by browsers. In particular, JMeter does not execute the Javascript found in HTML pages. Nor does it render the HTML pages as a browser does (it's possible to view the response as HTML etc., but the timings are not included in any samples, and only one sample in one thread is ever displayed at a time).
I'm monitoring the connect time and latency to connect from jmeter machine while running in GUI mode and that is in within acceptable limit.
Should we strictly follow non GUI mode even though I can able to perform load test with GUI mode?
I'm targeting 250 TPS and able to achieve that ..I have increased my memory and monitoring CPU and memory of load generator is below 60%.
Should I go for non GUI mode ?
The main limitation is that each event in the queue is being handled by a single event dispatch thread which will act as the bottleneck on your JMeter side.
My expectation is that your "250 TPS" look like:
while it should look like:
So check how does your load pattern look like using i.e. Transactions per Second listener (installable via JMeter Plugins Manager)
Also check how does your JVM look like especially when it comes to garbage collection, it can be done via i.e. JVisualVM, most probably you will see the same "chainsaw" pattern
You don't need to follow JMeter best practices, but
you may encounter issues to achieve specifc goals (as TPS)
your machine can't execute GUI or have low resources
you execute JMeter using a script or build tool as Jenkins
Also it's better to be familiar with JMeter CLI (non GUI) and its report capabilities
JMeter supports dashboard report generation to get graphs and statistics from a test plan.
Also it will be needed for using distributed testing
consider running multiple CLI JMeter instances on multiple machines using distributed mode (or not)
CLI also useful for Parameterising tests
The "loops" property can then be defined on the JMeter command-line:
jmeter … -Jloops=12
I wonder if some one solved the issue of browser multi thread with a request response script for load test
If you are going to use real Chrome and FF browsers for load test you can consider the following options:
Selenium Grid
Selenium-Grid allows you run your tests on different machines against different browsers in parallel. That is, running multiple tests at the same time against different machines running different browsers and operating systems. Essentially, Selenium-Grid support distributed test execution. It allows for running your tests in a distributed test execution environment.
Apache JMeter with the WebDriver Sampler plugin. This way you will be able to control concurrency and get performance metrics in form of HTML Reporting Dashboard.
Simulating web browser concurrency is something most load testing tools do very badly, if at all. We have tried to do this in k6 by letting each VU (virtual user) use multiple, concurrent TCP connections to fetch things in parallel. There is a special API function - http.batch() - that enables this functionality. http.batch() accepts multiple URLs as input parameters, and will fetch as many as possible in parallel.
Like Dmitri writes, Jmeter has a plugin that provides concurrency - sort of. However, what it actually does (unless I'm misinformed) is to spread out requests over multple VUs. Each VU will still only use one concurrent connection, which means that if you e.g. want to simulate 100 real browser users, you may need to fire up 1,000 VUs to do so realistically. This is not very different from what you would get with any other load testing tool, in my opinion: all of them allow you to start more VUs to create more concurrency and more traffic.
I'd say that apart from k6 and maybe one or perhaps two other tools (and Jmeter is not one of them), your only option if you want to really simulate the way browsers behave, is to use Selenium Grid or something similar to fire up a large number of real, actual browsers to do the load testing. The drawback is that real browsers are very expensive to run: they want lots of CPU and memory. But they provide the by far best browser "simulation".
We are using Apache JMeter for the performance testing of web application. Apparently response time is too high in comparison to loading page in browser during load. When we open the page during load it opens in 2 seconds however JMeter reports 70 seconds. I understand browser memory cache and disk cache are used in browser however isn't JMeter cache manager does same. How to assert it, comparing response header is one option. Any thoughts on this will be appreciated.
It may be wrong configuration in the script. There won't be much difference between web browser and Jmeter response times (browser rendering time is ignored in Jmeter, not a big factor but must be considered)
If you are using single Http Sampler for a web page and retrieving all resources in tha page, then select "Parallel Downloads" option to '6' in Http sampler advanced section. So, you are simulating the browser behaviour of parallel downloading of the resources like .js, .css, images etc.
If you recorded the script using Test Script Recorder, then there will be an Http Sampler for each resource requet for that page which will be sent sequentially, hence increase in response time. You might be in this case, as of now, there is no feature/option to send the http samplers in parallel. so I suggest using the approach of adding one sampler, use parallel download of resources option in Http Sampler advanced section.
Also, caching is an important factor which decides the response time. Adding Http Cache manager can solve the issue in jmeter. This simulates browser behaviour of caching. I don't think there will be huge difference b/w browser and jmeter in implementing caching althought may not be perfect.
The reason could be the lack of resources on JMeter machine or JMeter not being properly configured for producing high loads. JMeter default configuration is good for load tests development and debugging, you can run load tests up to certain amount of virtual users, but if you need to conduct a really high loads - you need to perform some configuration changes.
First of all, double check my guess using jvisualvm and your operating system monitoring tools (there is PerfMon JMeter Plugin which can be used for monitoring different metrics on application under test and JMeter load generators sides). If it is the case - take the next steps to get the most performance of your JMeter installation:
Increase JVM Heap Size, NewSize, switch to ConcurrentMarkSweep Garbage Collector.
Run your test in non-GUI mode.
Disable all the listeners during the test.
Follow other recommendations from 9 Easy Solutions for a JMeter Load Test “Out of Memory” Failure article.
I am beginner for jmeter and I configured and run the script with help of Google materials but I am not sure about picking the right listener for the performance testing and metrics in the graph.
can you please guide me to add respective listeners and what kind of listeners to be added for Application server,database server,network server,web server testing?
Thanks for help
JMeter is load testing tool and not a profiler. So there are no specific listeners for application server,DB server and all.
It works on http/https requests to produce load on target server. While scripting you can have as many listeners as you want to verify the script correctness and sample test runs.
But while actual load test minimal no. of listeners should be used. Listeners are for presenting the data which are cpu,memory intensive especially view results tree, view results table etc. should be avoided in actual load test.
Test should be carried out in non-ui mode for heavy load generation. Please have a look at ctrl+H (help, press ctrl+h on any component and this will show help) for all components available in JMeter from JMeter. Then probably you should be able to decide which ones are best for you.
Hope this helps :)
If you want to monitor server-side components health the best option is using PerfMon extension available via JMeter Plugins. You can collect different performance metrics like:
CPU usage
RAM usage
Network IO
Disk IO
In regards to JMeter bundled listeners: you can use all of them, but after tests execution. All the listeners are able to read .jtl results file and populate tables, graphs, etc. from it. For more recommendations see JMeter Performance and Tuning Tips guide