input: add support for upstream configuration for input client plugins.

[pwhelan]

Summary

Add support for upstream configuration for client input plugins.

Description

Client side input plugins like in_health and in_kubernetes_events use the upstream API but the property check for input plugins only applies downstream configuration checks. This pull request checks the plugin flags to see which one applies, either the downstream or upstream configuration map.

This allows setting upstream configuration settings for FLB_INPUT_NET plugins (as opposed to FLB_INPUT_NET_SERVER). This can be used for instance to be able workaround problems with the asynchronous DNS code by settings net.dns.resolver to LEGACY.

The full list of settings includes:

• net.dns.mode
• net.dns.resolver
• net.dns.prefer_ipv4
• net.dns.prefer_ipv6
• net.keepalive
• net.keepalive_idle_timeout
• net.tcp_keepalive
• net.tcp_keepalive_time
• net.tcp_keepalive_interval
• net.tcp_keepalive_probes
• net.io_timeout
• net.connect_timeout
• net.connect_timeout_log_error
• net.source_address
• net.keepalive_max_recycle
• net.max_worker_connections

Without this patch only the downstream settings can be applied to these plugins. This does not seem to me like the right fit. These include:

• net.share_port
• net.io_timeout
• net.accept_timeout
• net.accept_timeout_log_error
• net.keepalive

Notes

I have not added a check to make sure that not both flags, FLB_INPUT and FLB_INPUT_SERVER, are set on a plugin. In this case the downstream configuration map would be used. There should probably be a check, earlier than flb_input_net_property_check, that actually checks that both flags are not set.

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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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[github-actions]

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[edsiper]

moving it to the next milestone

[pwhelan]

@edsiper is this patch being looked at for the current milestone?