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https://issues.apache.org/jira/browse/HADOOP-15250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16372818#comment-16372818
 ] 

Greg Senia commented on HADOOP-15250:
-------------------------------------

[~ste...@apache.org] I think by binding to what is resolved by DNS you 
inherently break the ability to do Multi-homing with a routable and 
non-routable networks where you have split view DNS as in our case. We actually 
ran this design two years ago up the support chain of our Hadoop Vendor and was 
passed as being just fine. So the thought with splitview DNS is as follows: the 
server interface is resolved to ha21d52mn.unit.hdp.example.com when outside the 
cluster when inside the cluster ha21d52mn.unit.hdp.newyorklife.com is resolved 
to the cluster networks interface this was why we went with the DNS split views 
to support multi-homing correctly. If this functionality is NOT supported than 
Hadoop Project should remove the multi-homing features as things going to 
remote clusters will not work as shown by my trace/logs above. As Unit/Dev 
Cluster Network is not routable to our Tech/Test Cluster Network. So traffic 
would have to go out the server interfaces to get to another cluster hence why 
the splitview DNS is valid and a fix along these lines should at least allow a 
flag like the server components do to bind to 0.0.0.0. I do see HADOOP-7215 is 
what introduced this but I don't think multi-homing was thought about when this 
code was implemented and this code is really is only checking for null's.  So 
if this is not the right place than I think a solution needs to be determined 
to determine how to allow a Client to bind without using a specific IP/hostname 
as that is not a valid method with a multi-homed network. Also hadoop traffic 
destined for other hosts in the cluster would go via the cluster network and 
allow from use of jumbo frames as its not routable.

So when my co-workers and I decided to test this scenario out we modifed the 
code to allow traffic to bind to a valid local address depending on where the 
traffic needs to be destined this patch is working in our tech/test cluster. As 
the java.net.Socket doc shows you can run bind and it will bind to a valid 
local address. I mean attempting to bind outside of the OS opens up risks like 
we are hitting with distcp attempting to bind to an invalid source address that 
is non-routable

[https://docs.oracle.com/javase/8/docs/api/java/net/Socket.html#bind-java.net.SocketAddress-]

 

public void bind(

[SocketAddress|https://docs.oracle.com/javase/8/docs/api/java/net/SocketAddress.html]

 bindpoint) throws

[IOException|https://docs.oracle.com/javase/8/docs/api/java/io/IOException.html]
Binds the socket to a local address.If the address is {{null}}, then the system 
will pick up an ephemeral port and a valid local address to bind the socket.

 

 

 
|/**|
| | * Checks if {@code host} is a local host name and return {@link 
InetAddress}|
| | * corresponding to that address.|
| | * |
| | * @param host the specified host|
| | * @return a valid local {@link InetAddress} or null|
| | * @throws SocketException if an I/O error occurs|
| | */|
| |public static InetAddress getLocalInetAddress(String host)|
| |throws SocketException {|
| |if (host == null) {|
| |return null;|
| |}|
| |InetAddress addr = null;|
| |try {|
| |addr = SecurityUtil.getByName(host);|
| |if (NetworkInterface.getByInetAddress(addr) == null) {|
| |addr = null; // Not a local address|
| |}|
| |} catch (UnknownHostException ignore) \{ }|
| |return addr;|
| |}|

> 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
>            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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