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https://issues.apache.org/jira/browse/HBASE-12141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14156860#comment-14156860
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Andrew Purtell commented on HBASE-12141:
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... which could explain fragmentation, I think. The MTU of OpenVPN tunnels will
be less than normal by packet header + tunnel protocol overheads and possibly
not subject to PMTU discovery. I'd wager our channel handler is being invoked
with the first fragment is received so the PB is truncated but the remainder
will show up soon.
> ClusterStatus message might exceed max datagram payload limits
> --------------------------------------------------------------
>
> Key: HBASE-12141
> URL: https://issues.apache.org/jira/browse/HBASE-12141
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.98.3
> Reporter: Andrew Purtell
>
> The multicast ClusterStatusPublisher and its companion listener are using
> datagram channels without any framing. I think this is an issue because
> Netty's ProtobufDecoder expects a complete PB message to be available in the
> ChannelBuffer yet ClusterStatus messages can be large and might exceed the
> maximum datagram payload size. As one user reported on list:
> {noformat}
> org.apache.hadoop.hbase.client.ClusterStatusListener - ERROR - Unexpected
> exception, continuing.
> com.google.protobuf.InvalidProtocolBufferException: Protocol message tag had
> invalid wire type.
> at
> com.google.protobuf.InvalidProtocolBufferException.invalidWireType(InvalidProtocolBufferException.java:99)
> at
> com.google.protobuf.UnknownFieldSet$Builder.mergeFieldFrom(UnknownFieldSet.java:498)
> at
> com.google.protobuf.GeneratedMessage.parseUnknownField(GeneratedMessage.java:193)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClusterStatusProtos$ClusterStatus.<init>(ClusterStatusProtos.java:7554)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClusterStatusProtos$ClusterStatus.<init>(ClusterStatusProtos.java:7512)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClusterStatusProtos$ClusterStatus$1.parsePartialFrom(ClusterStatusProtos.java:7689)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClusterStatusProtos$ClusterStatus$1.parsePartialFrom(ClusterStatusProtos.java:7684)
> at
> com.google.protobuf.AbstractParser.parsePartialFrom(AbstractParser.java:141)
> at
> com.google.protobuf.AbstractParser.parseFrom(AbstractParser.java:176)
> at
> com.google.protobuf.AbstractParser.parseFrom(AbstractParser.java:182)
> at
> com.google.protobuf.AbstractParser.parseFrom(AbstractParser.java:49)
> at
> org.jboss.netty.handler.codec.protobuf.ProtobufDecoder.decode(ProtobufDecoder.java:122)
> at
> org.jboss.netty.handler.codec.oneone.OneToOneDecoder.handleUpstream(OneToOneDecoder.java:66)
> at
> org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:268)
> at
> org.jboss.netty.channel.socket.oio.OioDatagramWorker.process(OioDatagramWorker.java:52)
> at
> org.jboss.netty.channel.socket.oio.AbstractOioWorker.run(AbstractOioWorker.java:73)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> The javadoc for ProtobufDecoder says:
> {quote}
> Decodes a received ChannelBuffer into a Google Protocol Buffers Message and
> MessageLite. Please note that this decoder must be used with a proper
> FrameDecoder such as ProtobufVarint32FrameDecoder or
> LengthFieldBasedFrameDecoder if you are using a stream-based transport such
> as TCP/IP.
> {quote}
> and even though we are using a datagram transport we have related issues,
> depending on what the sending and receiving OS does with overly large
> datagrams:
> - We may receive a datagram with a truncated message
> - We may get an upcall when processing one fragment of a fragmented datagram,
> where the complete message is not available yet
> - We may not be able to send the overly large ClusterStatus in the first
> place. Linux claims to do PMTU and return EMSGSIZE if a datagram packet
> payload exceeds the MTU, but will send a fragmented datagram if PMTU is
> disabled. I'm surprised we have the above report given the default is to
> reject overly large datagram payloads, so perhaps the user is using a
> different server OS or Netty datagram channels do their own fragmentation (I
> haven't checked).
> In any case, the server and client pipelines are definitely not doing any
> kind of framing. This is the multicast status listener from 0.98 for example:
> {code}
> b.setPipeline(Channels.pipeline(
> new
> ProtobufDecoder(ClusterStatusProtos.ClusterStatus.getDefaultInstance()),
> new ClusterStatusHandler()));
> {code}
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