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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12141) ClusterStatus message might exceed max datagram payload limits
Date Thu, 02 Oct 2014 17:50:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14156860#comment-14156860

Andrew Purtell commented on HBASE-12141:

... 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,
> 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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