Add Zstd compression support to S3 plugin (#439)

adds support for Zstd compression in the Fluentd S3 plugin.

Changes

- Implemented Zstd compression using the `zstd-ruby` library.
- Introduced the `ZstdCompressor` class to handle log compression before uploading to S3.
- Updated the example configuration to demonstrate the use of `store_as zstd`.
- Ensured that the `Zstd` module is properly loaded to avoid uninitialized constant errors.

Why this feature?

Zstd compression provides a better compression ratio and performance compared to gzip, making it a valuable option for users who want efficient log storage on S3.

---------

Signed-off-by: dependabot[bot] <[email protected]>
Signed-off-by: yongwoo.kim <[email protected]>
Signed-off-by: ddukbg <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: yongwoo.kim <[email protected]>
Co-authored-by: Daijiro Fukuda <[email protected]>

.github/workflows/linux.yml

@@ -23,6 +23,6 @@ jobs:
       env:
         CI: true
       run: |
-        gem install bundler rake
+        gem install rake
         bundle install --jobs 4 --retry 3
         bundle exec rake test

fluent-plugin-s3.gemspec

@@ -19,6 +19,7 @@ Gem::Specification.new do |gem|
   gem.add_dependency "fluentd", [">= 0.14.22", "< 2"]
   gem.add_dependency "aws-sdk-s3", "~> 1.60"
   gem.add_dependency "aws-sdk-sqs", "~> 1.23"
+  gem.add_dependency 'zstd-ruby'
   gem.add_development_dependency "rake", ">= 0.9.2"
   gem.add_development_dependency "test-unit", ">= 3.0.8"
   gem.add_development_dependency "test-unit-rr", ">= 1.0.3"

lib/fluent/plugin/s3_compressor_zstd.rb

@@ -0,0 +1,30 @@
+require 'zstd-ruby'
+
+module Fluent::Plugin
+  class S3Output
+    class ZstdCompressor < Compressor
+      S3Output.register_compressor('zstd', self)
+
+      config_section :compress, param_name: :compress_config, init: true, multi: false do
+        desc "Compression level for zstd (1-22)"
+        config_param :level, :integer, default: 3
+      end
+
+      def ext
+        'zst'.freeze
+      end
+
+      def content_type
+        'application/x-zst'.freeze
+      end
+
+      def compress(chunk, tmp)
+        compressed = Zstd.compress(chunk.read, level: @compress_config.level)
+        tmp.write(compressed)
+      rescue => e
+        log.warn "zstd compression failed: #{e.message}"
+        raise
+      end
+    end
+  end
+end

test/test_out_s3.rb

@@ -109,6 +109,18 @@ def test_configure_with_mime_type_lzo
       assert(e.is_a?(Fluent::ConfigError))
     end
 
+    data('level default' => nil,
+         'level 1' => 1)
+    def test_configure_with_mime_type_zstd(level)
+      conf = CONFIG.clone
+      conf << "\nstore_as zstd\n"
+      conf << "\n<compress>\nlevel #{level}\n</compress>\n" if level
+      d = create_driver(conf)
+      assert_equal 'zst', d.instance.instance_variable_get(:@compressor).ext
+      assert_equal 'application/x-zst', d.instance.instance_variable_get(:@compressor).content_type
+      assert_equal (level || 3), d.instance.instance_variable_get(:@compressor).instance_variable_get(:@compress_config).level
+    end
+
     def test_configure_with_path_style
       conf = CONFIG.clone
       conf << "\nforce_path_style true\n"
@@ -456,6 +468,33 @@ def test_write_with_custom_s3_object_key_format_containing_hex_random_placeholde
     FileUtils.rm_f(s3_local_file_path)
   end
 
+  def test_write_with_zstd
+    setup_mocks(true)
+    s3_local_file_path = "/tmp/s3-test.zst"
+
+    expected_s3path = "log/events/ts=20110102-13/events_0-#{Socket.gethostname}.zst"
+
+    setup_s3_object_mocks(s3_local_file_path: s3_local_file_path, s3path: expected_s3path)
+
+    config = CONFIG_TIME_SLICE + "\nstore_as zstd\n"
+    d = create_time_sliced_driver(config)
+
+    time = event_time("2011-01-02 13:14:15 UTC")
+    d.run(default_tag: "test") do
+      d.feed(time, { "a" => 1 })
+      d.feed(time, { "a" => 2 })
+    end
+
+    File.open(s3_local_file_path, 'rb') do |file|
+      compressed_data = file.read
+      uncompressed_data = Zstd.decompress(compressed_data)
+      expected_data = %[2011-01-02T13:14:15Z\ttest\t{"a":1}\n] +
+                      %[2011-01-02T13:14:15Z\ttest\t{"a":2}\n]
+      assert_equal expected_data, uncompressed_data
+    end
+    FileUtils.rm_f(s3_local_file_path)
+  end
+
   class MockResponse
     attr_reader :data