s3 から file にデータを格納するときに遭遇したエラー（これでは落ちない）

output.txt

embulk -J-Dio.netty.leakDetectionLevel=advanced run config.yml -b embulk-bundle
...
2016-02-02 23:25:14.309 +0900 [ERROR] (task-0311): LEAK: ByteBuf.release() was not called before it's garbage-collected.
Recent access records: 0
Created at:
        io.netty.util.ResourceLeakDetector.open(ResourceLeakDetector.java:163)
        io.netty.buffer.AbstractByteBufAllocator.toLeakAwareBuffer(AbstractByteBufAllocator.java:42)
        io.netty.buffer.PooledByteBufAllocator.newHeapBuffer(PooledByteBufAllocator.java:228)
        io.netty.buffer.AbstractByteBufAllocator.heapBuffer(AbstractByteBufAllocator.java:136)
        io.netty.buffer.AbstractByteBufAllocator.heapBuffer(AbstractByteBufAllocator.java:127)
        io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:85)
        org.embulk.exec.PooledBufferAllocator.allocate(PooledBufferAllocator.java:37)
        org.embulk.spi.PageBuilder.newBuffer(PageBuilder.java:53)
        org.embulk.spi.PageBuilder.<init>(PageBuilder.java:48)
        org.embulk.standards.CsvParserPlugin.run(CsvParserPlugin.java:242)
        org.embulk.spi.FileInputRunner.run(FileInputRunner.java:154)
        org.embulk.spi.util.Executors.process(Executors.java:67)
        org.embulk.spi.util.Executors.process(Executors.java:42)
        org.embulk.exec.LocalExecutorPlugin$DirectExecutor$1.call(LocalExecutorPlugin.java:184)
        org.embulk.exec.LocalExecutorPlugin$DirectExecutor$1.call(LocalExecutorPlugin.java:180)
        java.util.concurrent.FutureTask.run(FutureTask.java:262)
        java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        java.lang.Thread.run(Thread.java:745)