Documentation for byte-based ingestion limits in Agent

[kilfoyle]

Agent (and Beats) output will be limitable by bytes, as an addition to current events-based limits.

Proposal document

We'd need to document:

• The new output settings:

  • bulk_max_bytes
  • queue.mem.bytes
  • queue.disk.input_memory_byte_limit
  • queue.disk.output_memory_byte_limit

• Resolution between conflicting settings (see "Interaction with existing defaults" section):

  • If any byte-based parameters are explicitly configured, all event-based defaults are ignored.
  • If any event-based limits are explicitly configured, all byte-based defaults are ignored.
  • If neither parameter type is explicitly configured, fall back on the global default (currently event-based).

It seems all settings will apply to Elasticsearch only, for now, with Logstash TBD.

Related Beats issue: https://github.com/elastic/beats/issues/30069