Fix invalid message polluting subsequent message

Signed-off-by: Satoshi Matsumoto <[email protected]>

Author: kaorimatz

lib/fluent/logger/fluent_logger.rb

@@ -231,8 +231,9 @@ def to_msgpack(msg)
                   @packer.pack(msg).to_s
                 rescue NoMethodError
                   JSON.parse(JSON.generate(msg)).to_msgpack
+                ensure
+                  @packer.clear
                 end
-          @packer.clear
           res
         }
       end

spec/fluent_logger_spec.rb

@@ -205,6 +205,10 @@
         expect(fluentd.queue.last).to be_nil
         logger_io.rewind
         logger_io.read =~ /FluentLogger: Can't convert to msgpack:/
+
+        logger.post('tag', { 'a' => 'b' })
+        fluentd.wait_transfer
+        expect(fluentd.queue.last).to eq ['logger-test.tag', { 'a' => 'b' }]
       }
 
       it ('should raise an error when second argument is non hash object') {