Load Testing with Vegeta

Load Testing Overview

Load testing allows testing the behaviour of an application under real conditions by simulating concurrent user requests. This can help to determine the behaviour of an application when multiple users access it simultaneously. This tutorial shows how to use Vegeta, an open source application written in the Go programming language, to run load testings on an application.

The following problems can be identified with the help of load testing, before moving an application into a production environment:

  • Response time checking for each request
  • Performance of the overall system under different loads
  • Database performances under heavy loads
  • Verification if load balancing is working as designed
  • Network latency between the client and the application
  • Performance limitations due the technical specifications of the instances used

Downloading and Installing Vegeta

1 . Connect to your server via SSH

2 . Download the latest Vegeta binary:

wget https://github.com/tsenart/vegeta/releases/download/cli%2Fv12.5.1/vegeta-12.5.1-linux-amd64.tar.gz

3 . Unpack the binary file:

tar xfz vegeta-12.5.1-linux-amd64.tar.gz

4 . Move the binary file into /usr/bin to make it available system-wide:

mv vegeta /usr/bin/vegeta

Running a Load Test with Vegeta

To run a load test during 120 seconds, run the following command:

echo "GET http://<application_url>/" | vegeta attack -duration=120s | tee results.bin | vegeta report

The command above will return a report like the following:

Requests      [total, rate]            6000, 50.01
Duration      [total, attack, wait]    2m0.072491358s, 1m59.980003112s, 92.488246ms
Latencies     [mean, 50, 95, 99, max]  76.235976ms, 72.996349ms, 109.192641ms, 133.960662ms, 187.907358ms
Bytes In      [total, mean]            65862000, 10977.00
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  100.00%
Status Codes  [code:count]             200:6000
Error Set:
  • Requests shows the total number of requests sent during the test and the rate of the requests
  • Duration shows the total duration of the test, the attack period simulating load on the application and the wait time
  • Latencies shows the mean latency, 50th, 95th an 99th percentiles, respectively, of the latencies of all requests in an attack as well as the maximum latency recognized.
  • Bytes In and Bytes Out shows:
    • The total number of bytes sent (out) or received (in) with the request or response bodies.
    • The mean number of bytes sent (out) or received (in) with the request or response bodies.
  • Success shows the percentiles of successful requests sent to the application
  • Status Codes provides a counter of the HTTP response codes received and their occurrence. A 0 status codes mean a request failed to be sent.

As visible in the example above, 100 % of the requests sent to the application were successful.

Following another result:

Requests      [total, rate]            6000, 50.01
Duration      [total, attack, wait]    2m9.500461177s, 1m59.980081991s, 9.520379186s
Latencies     [mean, 50, 95, 99, max]  843.903272ms, 77.954318ms, 3.744635321s, 25.164627897s, 30.000611567s
Bytes In      [total, mean]            62842863, 10473.81
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  95.38%
Status Codes  [code:count]             0:45  200:5723  500:33  502:13  503:186
Error Set:
500 Internal Server Error
502 Bad Gateway
Get http://<application_url>/: EOF
503 Service Unavailable
Get http://<application_url>/: net/http: request canceled (Client.Timeout exceeded while awaiting headers)

As visible in the output above, only 95.38% of the requests sent to the application were successful. In the Status Code section, it is visible that 5723 requests were successful (HTTP Code 200), 186 requests received an HTTP 503 error, and 13 requests received an HTTP 502 error.

These results show that the application has trouble handling the load and needs optimization.

Setting up a Target File

Vegeta also supports multiple targets to attack an application with multiple endpoints (i.e., an API) simultaneously.

1 . Create a target file and open it in a text editor:

nano target.list

2 . Put the different endpoints into it:

GET http://<application_url>/list/user/1
GET http://<application_url>/list/user/2
GET http://<application_url>/list/user/3

It is also possible to define POST or PUT commands into the file.

POST http://<application_url>/create/newuser/
Content-Type: application/json

The content of the file /path/to/newuser.json contains the body of the request:

  "name": "Peter";
  "lastname": "Smith";
  "email": "psmith@example.com"

2 . Run Vegeta, the -duration flag specifies the duration of the attack, the -rate flag defines the number of requests per time unit (the default value is set to 50/1s):

vegeta attack -duration=5s -rate=5 -targets=target.list

Generating a Report

Every load test executed to collect data that can be saved in an output file using the -output parameter.

The data collected during each load test is stored in an output file.

1 . Run an attack in Vegeta. The default filename of the output file is results.bin. It can be specified to any name with the -output flag:

vegeta attack -duration=120s -rate=100 -targets=target.list -output=attack-5.bin

2 . Generate the HTML report and plot with the vegeta plot command. The -title flag allows specifying a title for the plot.

vegeta plot -title=Attack%20Results attack-5.bin > results.html

3 . Open the HTML file in a web browser to view the plot:

Vegeta Plot

4 . Alternatively, it is also possible to generate the report as JSON output:

vegeta report -type=json results.bin

Returning a JSON output as follows:



5 . To view the report directly in the terminal, run:

vegeta report results.bin

Which provides an report in the format seen in the first steps:

Requests      [total, rate]            12000, 100.01
Duration      [total, attack, wait]    1m59.990299357s, 1m59.989905493s, 393.864µs
Latencies     [mean, 50, 95, 99, max]  418.193µs, 393.268µs, 523.664µs, 737.809µs, 13.47979ms
Bytes In      [total, mean]            7344000, 612.00
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  100.00%
Status Codes  [code:count]             200:12000
Error Set:

For more information about Vegeta, refer to the official documentation.

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