Motivation:
DefaultHttpDataFactory uses HttpRequest as map keys.
Because of the implementation of "hashCode"" and "equals" in DefaultHttpRequest,
if we use normal maps, HttpDatas of different requests may end up in the same map entry,
causing cleanup bug.
Consider this example:
- Suppose that request1 is equal to request2, causing their HttpDatas to be stored in one single map entry.
- request1 is cleaned up first, while request2 is still being decoded.
- Consequently request2's HttpDatas are suddenly gone, causing NPE, or worse loss of data.
This bug can be reproduced by starting the HttpUploadServer example,
then run this command:
ab -T 'application/x-www-form-urlencoded' -n 100 -c 5 -p post.txt http://localhost:8080/form
post.txt file content:
a=1&b=2
There will be errors like this:
java.lang.NullPointerException
at io.netty.handler.codec.http.multipart.MemoryAttribute.getValue(MemoryAttribute.java:64)
at io.netty.handler.codec.http.multipart.MixedAttribute.getValue(MixedAttribute.java:243)
at io.netty.example.http.upload.HttpUploadServerHandler.writeHttpData(HttpUploadServerHandler.java:271)
at io.netty.example.http.upload.HttpUploadServerHandler.readHttpDataChunkByChunk(HttpUploadServerHandler.java:230)
at io.netty.example.http.upload.HttpUploadServerHandler.channelRead0(HttpUploadServerHandler.java:193)
at io.netty.example.http.upload.HttpUploadServerHandler.channelRead0(HttpUploadServerHandler.java:66)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102)
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:284)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1412)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:943)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:141)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:645)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:580)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:497)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:459)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(Thread.java:748)
Modifications:
Keep identity of requests by using IdentityHashMap
Result:
DefaultHttpDataFactory is fixed.
The ConcurrentHashMap is replaced with a synchronized map, but I think the performance won't be affected much in real web apps.
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