ByteBuf.release() was not called before it's garbage-collected

[zhouzq]

I am using Lettuce 5.1.2.RELEASE + Netty 4.1.28.Final and see the following error.

2018-11-24 10:23:06.710|[lettuce-epollEventLoop-10-24]|ERROR|[Slf4JLogger.java:171]|LEAK: ByteBuf.release() was not called before it's garbage-collected. See http://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records:
Created at:
        io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:331)
        io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:185)
        io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:176)
        io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:113)
        io.lettuce.core.protocol.CommandArgs$KeyArgument.encode(CommandArgs.java:656)
        io.lettuce.core.protocol.CommandArgs.encode(CommandArgs.java:346)
        io.lettuce.core.protocol.Command.encode(Command.java:119)
        io.lettuce.core.protocol.AsyncCommand.encode(AsyncCommand.java:185)
        io.lettuce.core.cluster.ClusterCommand.encode(ClusterCommand.java:92)
        io.lettuce.core.protocol.CommandEncoder.encode(CommandEncoder.java:90)
        io.lettuce.core.protocol.CommandEncoder.encode(CommandEncoder.java:75)
        io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107)
        io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
        io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
        io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816)
        io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723)
        io.lettuce.core.protocol.CommandHandler.writeSingleCommand(CommandHandler.java:414)
        io.lettuce.core.protocol.CommandHandler.write(CommandHandler.java:345)
        io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738)
        io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730)
        io.netty.channel.AbstractChannelHandlerContext.access$1900(AbstractChannelHandlerContext.java:38)
        io.netty.channel.AbstractChannelHandlerContext$AbstractWriteTask.write(AbstractChannelHandlerContext.java:1081)
        io.netty.channel.AbstractChannelHandlerContext$WriteAndFlushTask.write(AbstractChannelHandlerContext.java:1128)
        io.netty.channel.AbstractChannelHandlerContext$AbstractWriteTask.run(AbstractChannelHandlerContext.java:1070)
        io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
        io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)
        io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:322)
        io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
        io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
        java.lang.Thread.run(Thread.java:748)

It seems the leak is from the invoke command.

[stillerrr]

I think we need add "try catch finally" in this place: io.lettuce.core.protocol.CommandArgs

if some exception happened before the release() method, the temp buffer would not be released.

for example: run mset() command and set a lot of key, it would take a long time, before the future callback, use the method completeExceptionally() throwing an exception, I think it would recurrent

[mp911de]

The attached stack trace originates from Lettuce 5.x, not the 4.x version. Thanks for reporting the issue.

[mp911de]

The improvement is in place now.

[zhouzq]

Thanks for your reply.