Too aggressive character escaping when using --log-format json

[xresch]

Brief summary

Situation:
Logs are used for analyzing and debugging our scripts and HTTP responses are therefore written to the log.
The log is very hard to read as html data is not human readable anymore when using --log-format json.

Data:

• To analyze if checks are working properly, which are verifying if a response body contains a certain string, it is crucial to be able to output the html response in a readable way.
• The K6 scripts are executed on a Monitoring Platform (Exense Step), which needs the --log-format json to be able to parse the outputs. So we cannot use --log-format raw.
• The json encoding of strings seems much to aggressive for logging outputs. The only characters you must escape are \, " and control codes (anything less than U+0020). Other characters like "<" and ">" as encoded as well to "\uxxxx" style, what blows up the whole output and makes it unreadable for ze human eyes.

Expected Behavior:
Console logs are still readable for a human with IT background.

Reproduction of issue:
K6 Script:

export default function () {
  console.log("<test>")
}

Output with --log-format json;

PS C:\tmp> k6 run .\reproducer.js --log-format json
{"level":"info","msg":"\u003ctest\u003e","source":"console","time":"2024-04-17T09:24:38+02:00"}

Output with --log-format raw;

PS C:\tmp> k6 run .\reproducer.js --log-format raw
<test>

k6 version

v0.48.0

OS

windows

Docker version and image (if applicable)

n/a

Steps to reproduce the problem

see description

Expected behaviour

see description

Actual behaviour

see description

[olegbespalov]

Hi @xresch !

Thanks for reporting this.

The issue comes from our logging library (github.com/sirupsen/logrus), which escapes HTML by default (DisableHTMLEscape: false, default is value).

k6/cmd/root.go

Line 252 in 144209f

c.globalState.Logger.SetFormatter(&logrus.JSONFormatter{})

However, we (k6 maintainers) need to discuss this, keeping in mind possible implications and also keeping in mind that we have this #2958

I'll get back to you 👍