Add JSON mode to Loki client

[juliusrickert]

I experienced problems with newlines in the text-based logging. This motivated me to add a simple JSON mode to the Loki client.

[dmachard]

Thanks for this PR.
Can you share some details regarding your issue with newlines ?

[juliusrickert]

Je vous en prie !
Thank you for developing and providing this piece of software.

First, a minor issue: the log lines end in \n, requiring the pattern to match it to end in \n.

But furthermore, I'm seeing domain names starting in "-n " (including the space), having newlines in them, etc. This is breaking my Loki pattern.
I'm not sure what the origin of this behaviour is (yet).

In general, I think it's dangerous to use client-provided data without escaping it (:eyes: Log4Shell). Thus, I think a JSON-based logger for Loki is beneficial.

[dmachard]

Could you share an example of a full line?
I haven't observed any issues on my side with text mode

[juliusrickert]

I think I can share a redacted example, but on Monday at the earliest, as I don't have access from my personal computer.

But I think that's kind of unrelated to adding this feature. What do you think about merging it?

[dmachard]

I just want to understand what happened in your case and why I haven't observed that in my side.

[juliusrickert]

No problem. Thank you for merging.

I'll open an issue about this if I have any news.

[dmachard]

Thank, You can also open a discussion regarding Loki with the DNS-Collector; it will be great to share implementation.