2014-01-16 14:48:19.226 PST [nioEventLoopGroup-8-1] ERROR o.o.o.protocol.impl.core.OFEncoder - null
java.lang.NullPointerException: null
at org.opendaylight.openflowjava.protocol.impl.util.ActionsSerializer.computeLengthOfActions(ActionsSerializer.java:325) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.util.InstructionsSerializer.computeInstructionsLength(InstructionsSerializer.java:169) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.serialization.factories.FlowModInputMessageFactory.computeLength(FlowModInputMessageFactory.java:69) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.serialization.factories.FlowModInputMessageFactory.computeLength(FlowModInputMessageFactory.java:28) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.util.ByteBufUtils.writeOFHeader(ByteBufUtils.java:114) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.serialization.factories.FlowModInputMessageFactory.messageToBuffer(FlowModInputMessageFactory.java:50) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.serialization.factories.FlowModInputMessageFactory.messageToBuffer(FlowModInputMessageFactory.java:28) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.serialization.SerializationFactory.messageToBuffer(SerializationFactory.java:36) ~[bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.core.OFEncoder.encode(OFEncoder.java:39) [bundlefile:na]
at org.opendaylight.openflowjava.protocol.impl.core.OFEncoder.encode(OFEncoder.java:25) [bundlefile:na]
at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:111) [bundlefile:na]
at io.netty.channel.DefaultChannelHandlerContext.invokeWrite(DefaultChannelHandlerContext.java:644) [bundlefile:na]
at io.netty.channel.DefaultChannelHandlerContext.access$2000(DefaultChannelHandlerContext.java:28) [bundlefile:na]
at io.netty.channel.DefaultChannelHandlerContext$WriteTask.run(DefaultChannelHandlerContext.java:891) [bundlefile:na]
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:354) [bundlefile:na]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:348) [bundlefile:na]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101) [bundlefile:na]
at java.lang.Thread.run(Thread.java:744) [na:1.7.0_45]

It looks like an element in the list (which is another list) is null and that is why this happens.

It looks like the NPE happens quite often but when it is invoked from OFEncoder#encode it is not being properly logged (I mean the stack trace is not being logged).

We need to ensure that the logging is prominent to ensure that such problems are identified faster.

To reproduce this problem do the following,

1. Build a controller distribution from the openflow plugin
2. Add a topology with mininet
3. h1 ping h2

You should see a NPE occur