out_loki: drop quotes after drop_single_key

[mifrost]

Removes quotes from log lines when line_format=json and drop_single_key=true

Resolves concerns raised in #3005

---

Testing

• Example configuration file for the change

[OUTPUT]
    Name              loki
    ....
    label_keys        $filename
    line_format       json
    remove_keys       filename
    Drop_single_key   true

• Debug log output from testing the change
  Before:
  "Nov 19 15:48:36 hostname telegraf: 2021-11-19T15:48:36Z D! [outputs.prometheus_client] Wrote batch of 82 metrics in 648.331µs"
  After:
  Nov 19 16:05:36 hostname telegraf: 2021-11-19T16:05:36Z D! [outputs.prometheus_client] Wrote batch of 82 metrics in 809.535µs

• Attached Valgrind output that shows no leaks or memory corruption was found

==5663== 
==5663== HEAP SUMMARY:
==5663==     in use at exit: 102,192 bytes in 3,426 blocks
==5663==   total heap usage: 36,646 allocs, 33,220 frees, 7,755,146 bytes allocated
==5663== 
==5663== LEAK SUMMARY:
==5663==    definitely lost: 0 bytes in 0 blocks
==5663==    indirectly lost: 0 bytes in 0 blocks
==5663==      possibly lost: 0 bytes in 0 blocks
==5663==    still reachable: 102,192 bytes in 3,426 blocks
==5663==         suppressed: 0 bytes in 0 blocks
==5663== Rerun with --leak-check=full to see details of leaked memory
==5663== 
==5663== For counts of detected and suppressed errors, rerun with: -v
==5663== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Documentation

• Documentation required for this feature

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[l2dy]

Valid JSON by definition has quotes. Could you use key_value line_format instead?

[github-actions]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[tsk9]

What is necessary to accept this PR?

The PR would help to prevent the needless quotes escape (\").

[l2dy]

In my opinion, a new option should be introduced instead of breaking the existing behavior that conforms to line_format.

[tsk9]

Something like a drop_single_key_as_raw_value configuration option?

[l2dy]

Something like a drop_single_key_as_raw_value configuration option?

It could also be a special value for the drop_single_key option. Either way, this is a stale PR and discussion should move elsewhere.

[github-actions]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days.