Discard the millisecond of the Time value

[Watson1978]

When it fails to serialize data to MsgPack format,
it falls back to part using JSON.parse(JSON.generate(msg)).to_msgpack.

fluent-logger-ruby/lib/fluent/logger/fluent_logger.rb

Lines 233 to 244 in 6bcebac

	def to_msgpack(msg)
	@mon.synchronize {
	res = begin
	@packer.pack(msg).to_s
	rescue NoMethodError
	JSON.parse(JSON.generate(msg)).to_msgpack
	ensure
	@packer.clear
	end
	res
	}
	end

The fallback part discard the millisecond of the Time value.
There are cases where people dislike it.

Example:

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "fluent-logger"
  gem "activesupport"
end

require 'active_support/json'

log = Fluent::Logger::FluentLogger.new(nil, :host => 'localhost', :port => 24224)

log.post("myapp.access", { user: "foo", created_at: Time.now })
log.post("myapp.access", { user: "foo", created_at: Time.now.as_json })

Beforehand, it preserves milliseconds converting with as_json.
(If active_support is loaded, to_json will invoke as_json automatically.)

This behavior is preferred by default.

2025-09-19 11:54:11.000000000 +0900 incoming: {"user":"foo","created_at":"2025-09-19 11:54:11 +0900"}
2025-09-19 11:54:11.000000000 +0900 incoming: {"user":"foo","created_at":"2025-09-19T11:54:11.828+09:00"}

We need to regist custom MsgPack packer for Time object, or something...