out_copy: Add copy_mode parameter. fix #2744

[repeatedly]

Signed-off-by: Masahiro Nakagawa [email protected]

Which issue(s) this PR fixes:
Fixes #2744

What this PR does / why we need it:
Add copy_mode parameter to control no / shallow / deep copy.

Here is benchmark code:

require 'benchmark/ips'
require 'active_support/core_ext/object/deep_dup'
require 'fluent/event'
require 'fluent/time'
require 'msgpack'

test1 = Fluent::MultiEventStream.new
100.times { |i|
  record = {"time" => 1362020400,"host" => "192.168.0.1","size" => 777,"method" => "PUT", "kubernetes" => {"pod" => "test", "labels" => {"app" => "foo"}}}
  test1.add(Fluent::EventTime.now, record)
}

def f_n(es)
  es
end

def f_d(es)
  es.dup
end

def f_dd(es)
  new_es = Fluent::MultiEventStream.new
  es.each { |time, record|
    new_es.add(time, record.deep_dup)
  }
  new_es
end

def f_mp(es)
  new_es = Fluent::MultiEventStream.new
  es.each { |time, record|
    new_es.add(time, MessagePack.unpack(MessagePack.pack(record)))
  }
  new_es
end

def f_mp2(es)
  packer = Fluent::MessagePackFactory.msgpack_packer
  times = []
  records = []
  es.each { |time, record|
    times << time
    packer.pack(record)
  }
  Fluent::MessagePackFactory.msgpack_unpacker.feed_each(packer.full_pack) { |record|
    records << record
  }
  Fluent::MultiEventStream.new(times, records)
end

def f_m(es)
  new_es = Fluent::MultiEventStream.new
  es.each { |time, record|
    new_es.add(time, Marshal.load(Marshal.dump(record)))
  }
  new_es
end

Benchmark.ips do |x|
  x.report "none" do
    f_n(test1)
  end

  x.report "dup" do
    f_d(test1)
  end

  x.report "deep_dup" do
    f_dd(test1)
  end

  x.report "msgpack" do
    f_mp(test1)
  end

  x.report "msgpack2" do
    f_mp2(test1)
  end

  x.report "marshal" do
    f_m(test1)
  end
end

result:

Warming up --------------------------------------
                none   375.217k i/100ms
                 dup     2.231k i/100ms
            deep_dup   241.000  i/100ms
             msgpack   215.000  i/100ms
            msgpack2   525.000  i/100ms
             marshal    78.000  i/100ms
Calculating -------------------------------------
                none     18.437M (± 5.8%) i/s -     91.928M in   5.007073s
                 dup     22.413k (± 5.7%) i/s -    113.781k in   5.095399s
            deep_dup      2.436k (± 5.9%) i/s -     12.291k in   5.065170s
             msgpack      2.163k (± 6.8%) i/s -     10.750k in   5.000194s
            msgpack2      5.314k (± 6.4%) i/s -     26.775k in   5.063501s
             marshal    784.487  (± 5.1%) i/s -      3.978k in   5.086555s

Docs Changes:
Add copy_mode parameter.

Release Note:
Same as title.