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https://issues.apache.org/jira/browse/HDFS-3148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13244302#comment-13244302
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Daryn Sharp commented on HDFS-3148:
-----------------------------------
Interesting. Were the 4 interfaces all configured for the same subnet?
Traffic will always come back on the interface for the bound ip, but outgoing
is supposedly subject to the standard routing table. It seems people are using
iptables contortions to force traffic out the interface for a bound ip. If the
interfaces are multi-homed to different subnets, does outbound go out the
correct interface?
> The client should be able to use multiple local interfaces for data transfer
> ----------------------------------------------------------------------------
>
> Key: HDFS-3148
> URL: https://issues.apache.org/jira/browse/HDFS-3148
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs client
> Reporter: Eli Collins
> Assignee: Eli Collins
> Attachments: hdfs-3148-b1.txt, hdfs-3148-b1.txt, hdfs-3148.txt,
> hdfs-3148.txt
>
>
> HDFS-3147 covers using multiple interfaces on the server (Datanode) side.
> Clients should also be able to utilize multiple *local* interfaces for
> outbound connections instead of always using the interface for the local
> hostname. This can be accomplished with a new configuration parameter
> ({{dfs.client.local.interfaces}}) that accepts a list of interfaces the
> client should use. Acceptable configuration values are the same as the
> {{dfs.datanode.available.interfaces}} parameter. The client binds its socket
> to a specific interface, which enables outbound traffic to use that
> interface. Binding the client socket to a specific address is not sufficient
> to ensure egress traffic uses that interface. Eg if multiple interfaces are
> on the same subnet the host requires IP rules that use the source address
> (which bind sets) to select the destination interface. The SO_BINDTODEVICE
> socket option could be used to select a specific interface for the connection
> instead, however it requires JNI (is not in Java's SocketOptions) and root
> access, which we don't want to require clients have.
> Like HDFS-3147, the client can use multiple local interfaces for data
> transfer. Since the client already cache their connections to DNs choosing a
> local interface at random seems like a good policy. Users can also pin a
> specific client to a specific interface by specifying just that interface in
> dfs.client.local.interfaces.
> This change was discussed in HADOOP-6210 a while back, and is actually
> useful/independent of the other HDFS-3140 changes.
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