config: throw an error if a configuration property is not applied.

[pwhelan]

Summary

Add a one-liner so if for some reason a property is not properly checked or applied an error is raised nonetheless.

With this configuration:

---
pipeline:
  inputs:
    - name: dummy
      dummy:
        message: '{"message: "my custom dummy"}'
  outputs:
    - name: stdout
      match: "*"
      format: json_lines

Without this change the fact that dummy is set as a key/value map is silently ignored, even though it is set as a string in the dummy plugin config_map. This change does not check the types but at least it does raise an error when the type is ignored, ie:

./bin/fluent-bit -c bad-dummy.yml
Fluent Bit v2.1.8
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/08/02 15:44:22] [error] [config] could not configure property 'dummy' on input plugin with section name 'dummy'
[2023/08/02 15:44:22] [ info] [fluent bit] version=2.1.8, commit=1d83649441, pid=766101
[2023/08/02 15:44:22] [ info] [storage] ver=1.2.0, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/08/02 15:44:22] [ info] [cmetrics] version=0.6.3
[2023/08/02 15:44:22] [ info] [ctraces ] version=0.3.1
[2023/08/02 15:44:22] [ info] [input:dummy:dummy.0] initializing
[2023/08/02 15:44:22] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2023/08/02 15:44:22] [ info] [sp] stream processor started
[2023/08/02 15:44:22] [ info] [output:stdout:stdout.0] worker #0 started
{"date":1691005462.537879,"message":"dummy"}
{"date":1691005463.537903,"message":"dummy"}
^C[2023/08/02 15:44:24] [engine] caught signal (SIGINT)
[2023/08/02 15:44:24] [ warn] [engine] service will shutdown in max 5 seconds
[2023/08/02 15:44:24] [ info] [input] pausing dummy.0
{"date":1691005464.537889,"message":"dummy"}
[2023/08/02 15:44:25] [ info] [engine] service has stopped (0 pending tasks)
[2023/08/02 15:44:25] [ info] [input] pausing dummy.0
[2023/08/02 15:44:25] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2023/08/02 15:44:25] [ info] [output:stdout:stdout.0] thread worker #0 stopped

This is the error that is reported in this case:

[2023/08/02 15:44:22] [error] [config] could not configure property 'dummy' on input plugin with section name 'dummy'

Fluent-bit continues on, but this is the default behaviour for any and all invalid properties.

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Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

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

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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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.

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