default behavior of dd_message_key from out_datadog is broken

[pmeier]

Bug Report

Documentation states

fluent-bit/plugins/out_datadog/datadog.c

Lines 536 to 542 in 2bef958

	{
	FLB_CONFIG_MAP_STR, "dd_message_key", NULL,
	0, FLB_TRUE, offsetof(struct flb_out_datadog, dd_message_key),
	"By default, the plugin searches for the key 'log' "
	"and remap the value to the key 'message'. "
	"If the property is set, the plugin will search the property name key."
	},

But the default behavior is not happening. If you leave this configuration option out, no processing is applied and thus by default the 'log' instead of the 'message' key is used. And since this format is not recognized by Datadog, the message does not show up at all.

We figured this out by configuring the plugin to send its data to a self-controlled HTTP server that does nothing but mirror back its input.

Expected behavior

Honor the default behavior described in the documentation.

Your Environment

• Version used: 3.0.7
• Environment name and version (e.g. Kubernetes? What version?): Kubernetes
• Filters and plugins: out_datadog

[patrick-stephens]

Please can you follow the issue template to capture all the relevant information like OS, target, what version of Fluent Bit, etc.?

[pmeier]

Done @patrick-stephens