[RUBY-119] eagerly require compressors

Author: Bulat Shakirzyanov

lib/cassandra.rb

@@ -324,10 +324,8 @@ def self.cluster_async(options = {})
 
       case compression
       when :snappy
-        require 'cassandra/compression/compressors/snappy'
         options[:compressor] = Compression::Compressors::Snappy.new
       when :lz4
-        require 'cassandra/compression/compressors/lz4'
         options[:compressor] = Compression::Compressors::Lz4.new
       else
         raise ::ArgumentError, ":compression must be either :snappy or :lz4, #{compression.inspect} given"

lib/cassandra/compression.rb

@@ -64,3 +64,6 @@ class Compressor
     end
   end
 end
+
+require 'cassandra/compression/compressors/snappy'
+require 'cassandra/compression/compressors/lz4'

lib/cassandra/compression/compressors/lz4.rb

@@ -16,12 +16,6 @@
 # limitations under the License.
 #++
 
-begin
-  require 'lz4-ruby'
-rescue LoadError => e
-  raise LoadError, %[LZ4 support requires the "lz4-ruby" gem: #{e.message}], e.backtrace
-end
-
 module Cassandra
   module Compression
     module Compressors
@@ -40,6 +34,14 @@ class Lz4 < Compressor
         # @param [Integer] min_size (64) Don't compress frames smaller than
         #   this size (see {#compress?}).
         def initialize(min_size=64)
+          unless defined?(::LZ4::Raw)
+            begin
+              require 'lz4-ruby'
+            rescue LoadError => e
+              raise LoadError, %[LZ4 support requires the "lz4-ruby" gem: #{e.message}], e.backtrace
+            end
+          end
+
           @algorithm = 'lz4'.freeze
           @min_size = min_size
         end

lib/cassandra/compression/compressors/snappy.rb

@@ -16,12 +16,6 @@
 # limitations under the License.
 #++
 
-begin
-  require 'snappy'
-rescue LoadError => e
-  raise LoadError, %[Snappy support requires the "snappy" gem: #{e.message}], e.backtrace
-end
-
 module Cassandra
   module Compression
     module Compressors
@@ -40,6 +34,14 @@ class Snappy < Compressor
         # @param [Integer] min_size (64) Don't compress frames smaller than
         #   this size (see {#compress?}).
         def initialize(min_size=64)
+          unless defined?(::Snappy)
+            begin
+              require 'snappy'
+            rescue LoadError => e
+              raise LoadError, %[Snappy support requires the "snappy" gem: #{e.message}], e.backtrace
+            end
+          end
+
           @algorithm = 'snappy'.freeze
           @min_size = min_size
         end