[exporter][batching] configuration and config validation for bytes based batching

[sfc-gh-sili]

Description

This PR adds config API that will be used for serialized bytes based batching.

type MinSizeConfig struct {
	MinSizeItems int `mapstructure:"min_size_items"`
	MinSizeBytes int `mapstructure:"min_size_bytes"`
}
type MaxSizeConfig struct {
	MaxSizeItems int `mapstructure:"max_size_items"`
	MaxSizeBytes int `mapstructure:"max_size_bytes"`
}

Link to tracking issue

#3262

Testing

Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.73%. Comparing base (9757ead) to head (4edf746).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #12154   +/-   ##
=======================================
  Coverage   91.73%   91.73%           
=======================================
  Files         463      463           
  Lines       24819    24834   +15     
=======================================
+ Hits        22767    22782   +15     
  Misses       1670     1670           
  Partials      382      382           

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[bogdandrutu]

What if we have a "Sizer"("SizerType") as enum with 3 values (request, items, bytes) and the "size" value instead?

[sfc-gh-sili]

Good idea. How about something like this:

type BatcherConfig struct {
	...
	minSize SizeConfig `mapstructure:"min_size"`
	maxSize SizeConfig `mapstructure:"max_size"`
}
type SizeConfig struct {
	sizer string `mapstructure:"sizer"`
	size int `mapstructure:"size"`
}
func (c SizeConfig) validate() {
	...
}

Does the option request mean that the request will implement its own sizing method?

[bogdandrutu]

Not sure if we need "sizer" in both min/max, since I don't think we need to accept different sizer for min and max.

[sfc-gh-sili]

I don't think we need to accept different sizer for min and max.

Good point. How about

type BatcherConfig struct {
	...
	sizer SizeType `mapstructure:",squash"`
	minSize int `mapstructure:"max_size"`
	maxSize int `mapstructure:"max_size"`
}
type SizerType struct {
	sizer string `mapstructure:"sizer"`
}
func (c SizerType) validate() {
}

[jmacd]

Why is "Sizer" a configuration string? What does it name, and how does the user configure it?