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CSV Variable Configuration

A CSV file consists of any number of records, separated by line breaks of some kind; each record consists of fields, separated by some other character or string, most commonly a literal comma or tab.

Each time a Virtual User is executed, it uses a line of the CSV file and gets one variable for each column. E.g. if you run a scenario for one hour, with a VU that takes 5 minutes to execute, you would need 12 lines in your CSV file to allow each VU ran to have its unique set of variables.

The CSV file parsing is configured in the Configuration tab. And the variables naming is done in the Column tab. The Column tab also shows a preview of the extracted values.

The following procedure explains how to change a CSV variable configuration:

  1. Click on the variable to update in the variables list,
  2. Enter a name and description,
  3. In the Configuration tab, select a CSV file to upload,
  4. Select encoding, delimiter and other options (explained bellow),
  5. Switch to Columns tab,
  6. For each column, type the name of the corresponding variable,
  7. Close the variable panel by clicking on the Close button positioned at the right left corner.

CSV Variable Configuration

Property name Description
Name The variable name. To inject it, use the ${...} syntax.
Description The variable description
File The CSV file of the variable
Shuffle Rows Shuffles the CSV file lines before executing the test
Encoding The CSV file encoding, leave blank if UTF-8
Delimiter The character or string used to separate the fields in the uploaded CSV file. Usually a comma
Allow quoted data A value may be enclosed in double-quotes if this option is selected
Sharing mode Private or Shared, if private each VU instance will use its own data set
Recycle values on EOF Should the file be re-read from the beginning when reaching its end? If set to false the value is set to <EOF> when the end of the file is reached
Stop VU on EOF Should the Virtual User be stopped when the end of the file is reached. Can only be activated if the Recycle values on EOF option is not

Note

If Allow quoted data is enabled, values in the CSV file may be enclosed in double-quotes. These are removed. E.g. you use a comma delimiter but one of your values contains a comma character. You can escape this value by placing it between quotes.

To include double-quotes within a quoted field, use two double-quotes. For example, with the CSV content (comma character used as a delimiter and quoted data allowed):

first,"second",last
1,2,3
1,"2,5","4""5"

Column one Column two Column three
first second last
1 2 3
1 2,5 4"5

Sharing mode

Private

Private

Selecting private means that each user will read the file sequentially on its own. If you have 2 values in your file login1 and login2 and set it on Recycle, the result would be:

Iteration Virtual user 1 Virtual user 2
1 login1 login1
2 login2 login2
3 login1 login1

Warning

If you use Shuffle rows before test execution?, we will only shuffle the file before the test. Which means that every user will still be using the same values in the same order. If that's not what you're looking for, you should try with Shared instead.

Shared

Shared

Shared means that the load generator will distribute a different value to each user when they ask for one. Of course that remains true as long as there are unique values left in the file. See end of file policy for more details. If you have 2 values in your file login1 and login2 and set it on Recycle, the result would be:

Iteration Virtual user 1 Virtual user 2
1 login1 login2
2 login1 login2
3 login2 login1

Since unique values are only guaranteed at the load generator level, we also split the CSV between load generators so that each one gets a unique list of values.

End of file policy

End of file

Upon reaching the last line of the file you can set the CSV variable to behave in two ways:

  • Recycle and loop back at the beginning of the file,
  • Stop VU meaning the number of users running during your test might drop down. If this happens, a message will be visible in the JMeter logs.

Columns

The column tab gives a preview of the first 8 values:

CSV Variable Columns

You can use it to check if your configuration gives the expected output.

Each column header is editable. It lets you name each of the variables. E.g. in the above screenshot, you could inject id using the ${id} syntax and value using ${value}.

Tip

You can leave empty column names. In this case the first row of the CSV file is used as variables names.

Skip to next line

CSV files in OctoPerf are parsed once every iteration. If you need to skip a line or just want to parse the whole CSV in one iteration, you can use the __CSVRead function.

CSV Read example

Example for a file named credential.csv:

  • ${__CSVRead(resources/credentials.csv,0)} will be replaced with the first column of the current line,
  • ${__CSVRead(resources/credentials.csv,1)} will be replaced with the second column of the current line,
  • ${__CSVRead(resources/credentials.csv,next())} will skip to the next line.

Info

Value distribution is not configurable, it will always be equivalent to shared. Meaning that it can skip lines because another thread/user might already have taken the next one.

Warning

This function does not use the CSV variables at all, it works on an earlier version of CSV variables. Because of that you do not need to create a CSV variable to use it, just provide the file.

CSV file splitting

Uniqueness

The first thing to understand on CSV splitting is that we need to provide a unique set of values to each load generator. It is the only way we can guarantee that each user has access to a unique value because the underlying JMeter will distribute values at load generator level.

Another important notion is that each user running will pick a new value every time he runs a new iteration. You can work around this by using Flow control actions, but if you need each user to have a unique value, you want the last user to start before the first ones start their next iteration. Unless of course you have more values in your CSV than the number of users running.

Load generators

So the first step is to assess how many load generators will be required for a test. We do that based on several criterias, mostly the number of concurrent users. If you are using your own On premise agents, check the provider configuration to understand how it works.

For instance when running a test with the following configuration:

  • Login with 500 concurrent users from Paris,
  • Login with 2 000 concurrent users from California,
  • Create account with 500 concurrent users from Sidney.

We will most likely end up using 4 load generators:

CSV Runtime

CSV Splitting

Now let's say we have a login.csv file and we want each user to pick a unique value during the test. To do that we configure it to shared on the CSV configuration page.

Now you might think that we can split the file in 4, send a each load generator a share and proceed with the test. This is when we run into a second issue, because out of the 4 load generators, only 3 of them run the login virtual user.

Generally speaking, at this stage, we need to assess out of all the load generators how many of them will use a particular file. We do this by scanning the VU for each column name configured in the CSV and when we find one we give a share of this CSV to the load generators running it. This means that if a CSV is in use by several different VU profiles we can still guarantee unique values to each one of them. Or course if you don't want that, you can just duplicate your CSV variables instead.

In our earlier example we need to split the CSV file in 3 shares. We do a modulo on the file, in our case picking 1 line out of 3 for each subset:

CSV Splitter

Warning

Each subset is of equal size. Since we cannot accurately predict how many users will end on each load generator they all get the same amount of values. That can be misleading if you have very different number of users running. For example 10 users on one side and 1000 on the other will get both half of the file. You can compensate for this by providing more values.

CSV file matching

The only step remaining is to send each load generator its share of the file:

CSV Matching

And in the background we edit each CSV variable to pick the new splitted file over the original CSV.