fix: Improve ZstdCompressor implementation

Signed-off-by: ddukbg <[email protected]>

lib/fluent/plugin/out_s3.rb

@@ -632,8 +632,6 @@ def compress(chunk, tmp)
     end
 
     class ZstdCompressor < Compressor
-      require 'zstd-ruby'
-
       DEFAULT_LEVEL = 3
 
       def initialize(level = nil)

test/test_out_s3.rb

@@ -467,28 +467,29 @@ def test_write_with_custom_s3_object_key_format_containing_hex_random_placeholde
   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
+
+    data = File.binread(s3_local_file_path)
+    begin
+      uncompressed = Zstd.decompress(data)
+      expected = %[2011-01-02T13:14:15Z\ttest\t{"a":1}\n] +
+                 %[2011-01-02T13:14:15Z\ttest\t{"a":2}\n]
+      assert_equal expected, uncompressed
+    ensure
+      FileUtils.rm_f(s3_local_file_path)
     end
-    FileUtils.rm_f(s3_local_file_path)
   end
 
   class MockResponse