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https://issues.apache.org/jira/browse/HADOOP-15250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16372896#comment-16372896
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Axton Grams commented on HADOOP-15250:
--------------------------------------

I work with Greg on the same clusters.  To add some color to the DNS/split view 
configuration:
 * DNS is configured with 2 views:
 ** Internal: Used by cluster machines to resolve Hadoop nodes to cluster 
network segment IP
 ** External: Used by non-cluster machines to resolve Hadoop nodes to routable 
network segment IP
 * All nodes with a presence on the cluster network resolve machines to the 
cluster (non-routable) IP address
 * All nodes without a presence on the cluster network resolve machines to the 
routable IP address

We implemented this pattern for the following reasons:
 * We can allow unfettered access (iptables/firewalld) between cluster nodes
 * We use jumbo frames on the cluster network to ease network load

You have to understand that the interface the service binds to is conditional 
depending on the origin of the traffic, not how the server knows itself 
according to DNS or Kerberos.  Different nodes know the server by the same name 
with different IP addresses, depending on whether they have a presence on the 
cluster network segment.  All Hadoop nodes know themselves by the cluster IP 
address, which is non-routable.

This design is compatible with the Linux network stack, DNS view practices, 
multi-homing practices, and all other related technology domains, just not 
Hadoop.

> Split-DNS MultiHomed Server Network Cluster Network IPC Client Bind Addr Wrong
> ------------------------------------------------------------------------------
>
>                 Key: HADOOP-15250
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15250
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ipc, net
>    Affects Versions: 2.7.3, 2.9.0, 3.0.0
>         Environment: Multihome cluster with split DNS and rDNS lookup of 
> localhost returning non-routable IPAddr
>            Reporter: Greg Senia
>            Priority: Critical
>         Attachments: HADOOP-15250.patch
>
>
> We run our Hadoop clusters with two networks attached to each node. These 
> network are as follows a server network that is firewalled with firewalld 
> allowing inbound traffic: only SSH and things like Knox and Hiveserver2 and 
> the HTTP YARN RM/ATS and MR History Server. The second network is the cluster 
> network on the second network interface this uses Jumbo frames and is open no 
> restrictions and allows all cluster traffic to flow between nodes. 
>  
> To resolve DNS within the Hadoop Cluster we use DNS Views via BIND so if the 
> traffic is originating from nodes with cluster networks we return the 
> internal DNS record for the nodes. This all works fine with all the 
> multi-homing features added to Hadoop 2.x
>  Some logic around views:
> a. The internal view is used by cluster machines when performing lookups. So 
> hosts on the cluster network should get answers from the internal view in DNS
> b. The external view is used by non-local-cluster machines when performing 
> lookups. So hosts not on the cluster network should get answers from the 
> external view in DNS
>  
> So this brings me to our problem. We created some firewall rules to allow 
> inbound traffic from each clusters server network to allow distcp to occur. 
> But we noticed a problem almost immediately that when YARN attempted to talk 
> to the Remote Cluster it was binding outgoing traffic to the cluster network 
> interface which IS NOT routable. So after researching the code we noticed the 
> following in NetUtils.java and Client.java 
> Basically in Client.java it looks as if it takes whatever the hostname is and 
> attempts to bind to whatever the hostname is resolved to. This is not valid 
> in a multi-homed network with one routable interface and one non routable 
> interface. After reading through the java.net.Socket documentation it is 
> valid to perform socket.bind(null) which will allow the OS routing table and 
> DNS to send the traffic to the correct interface. I will also attach the 
> nework traces and a test patch for 2.7.x and 3.x code base. I have this test 
> fix below in my Hadoop Test Cluster.
> Client.java:
>       
> |/*|
> | | * Bind the socket to the host specified in the principal name of the|
> | | * client, to ensure Server matching address of the client connection|
> | | * to host name in principal passed.|
> | | */|
> | |InetSocketAddress bindAddr = null;|
> | |if (ticket != null && ticket.hasKerberosCredentials()) {|
> | |KerberosInfo krbInfo =|
> | |remoteId.getProtocol().getAnnotation(KerberosInfo.class);|
> | |if (krbInfo != null) {|
> | |String principal = ticket.getUserName();|
> | |String host = SecurityUtil.getHostFromPrincipal(principal);|
> | |// If host name is a valid local address then bind socket to it|
> | |{color:#FF0000}*InetAddress localAddr = 
> NetUtils.getLocalInetAddress(host);*{color}|
> |{color:#FF0000} ** {color}|if (localAddr != null) {|
> | |this.socket.setReuseAddress(true);|
> | |if (LOG.isDebugEnabled()) {|
> | |LOG.debug("Binding " + principal + " to " + localAddr);|
> | |}|
> | |*{color:#FF0000}bindAddr = new InetSocketAddress(localAddr, 0);{color}*|
> | *{color:#FF0000}{color}* |*{color:#FF0000}}{color}*|
> | |}|
> | |}|
>  
> So in my Hadoop 2.7.x Cluster I made the following changes and traffic flows 
> correctly out the correct interfaces:
>  
> diff --git 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
>  
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> index e1be271..c5b4a42 100644
> --- 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> +++ 
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
> @@ -305,6 +305,9 @@
>    public static final String  IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY 
> = "ipc.client.fallback-to-simple-auth-allowed";
>    public static final boolean 
> IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT = false;
>  
> +  public static final String  IPC_CLIENT_NO_BIND_LOCAL_ADDR_KEY = 
> "ipc.client.nobind.local.addr";
> +  public static final boolean IPC_CLIENT_NO_BIND_LOCAL_ADDR_DEFAULT = false;
> +
>    public static final String IPC_CLIENT_CONNECT_MAX_RETRIES_ON_SASL_KEY =
>      "ipc.client.connect.max.retries.on.sasl";
>    public static final int    IPC_CLIENT_CONNECT_MAX_RETRIES_ON_SASL_DEFAULT 
> = 5;
> diff --git 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
>  
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> index a6f4eb6..7bfddb7 100644
> --- 
> a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> +++ 
> b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java
> @@ -129,7 +129,9 @@ public static void setCallIdAndRetryCount(int cid, int 
> rc) {
>  
>    private final int connectionTimeout;
>  
> +
>    private final boolean fallbackAllowed;
> +  private final boolean noBindLocalAddr;
>    private final byte[] clientId;
>    
>    final static int CONNECTION_CONTEXT_CALL_ID = -3;
> @@ -642,7 +644,11 @@ private synchronized void setupConnection() throws 
> IOException {
>                InetAddress localAddr = NetUtils.getLocalInetAddress(host);
>                if (localAddr != null) {
>                  this.socket.setReuseAddress(true);
> -                this.socket.bind(new InetSocketAddress(localAddr, 0));
> +                if (noBindLocalAddr) {
> +                  this.socket.bind(null);
> + } else {
> +                  this.socket.bind(new InetSocketAddress(localAddr, 0));
> +                }
>                }
>              }
>            }



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