Use block to output logs due to reduce memory usage

[Watson1978]

The many long duplicated logs seem to use a lot of memory at record.to_json in log.debug.

fluent-plugin-suppress/lib/fluent/plugin/filter_suppress.rb

Line 38 in d227121

log.debug "suppressed record: #{record.to_json}"

log.debug "log message" does not output the message with info log level.
However, the message have been evaluated.

If passes the block instead, log.debug will evaluate the block only when output the message.

Related to fluent/fluentd#4808

Reproduce

Fluentd configuration

<source>
  @type tail
  path "#{File.expand_path '~/tmp/access*.log'}"
  pos_file "#{File.expand_path '~/tmp/fluentd/access.log.pos'}"
  tag log
  <parse>
    @type none
  </parse>
</source>

<filter log.**>
    @type suppress
    log_suppress_interval 10
    num 1
    max_slot_num 10
    attr_keys short_message
</filter>

<match **>
  @type stdout
</match>

Log generate script

require "json"

path = File.expand_path("~/tmp/access.log")
File.open(path, "w") do |f|
  log = { "message": "a" * 500_000 }.to_json
  loop do
    f.puts log
    sleep 0.0001
  end
end

Result