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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9229) IPC: Retry on connection reset or socket timeout during SASL negotiation
Date Fri, 18 Jan 2013 18:48:14 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13557465#comment-13557465
] 

Kihwal Lee commented on HADOOP-9229:
------------------------------------

[~tlipcon] In this scenario, setupIOStreams() will throw an exception without retrying, because
handleSaslConnectionFailure() gives up. If the auth mode is kerberos, it will be retried,
but that's still outside of setupConnection() without involving handleConnectionFailure().
May be we should add a check for connection retry policy in handleSaslConnectionFailure().

[~sureshms] We've also seen this happening against AM. Since there are finite number of tasks,
retrying would have made the job succeed. This failure mode is particularly bad since clients
fail without retrying. For requests for which only one chance is allowed, this is fatal. Since
failed jobs get retried, the same situation will likely repeat. If all requests are eventually
served, the load will go away without doing more damage.  

I agree that if this condition is sustained, the cluster has bigger problem and no ipc-level
actions will solve that. But for transient overloads, we want the system to behave more gracefully.
One concern is server accepting too much connections and running out of FD, which causes all
kinds of bad things. This can be prevented by HADOOP-9137. 
                
> IPC: Retry on connection reset or socket timeout during SASL negotiation
> ------------------------------------------------------------------------
>
>                 Key: HADOOP-9229
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9229
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ipc
>    Affects Versions: 3.0.0, 2.0.3-alpha, 0.23.7
>            Reporter: Kihwal Lee
>
> When an RPC server is overloaded, incoming connections may not get accepted in time,
causing listen queue overflow. The impact on client varies depending on the type of OS in
use. On Linux, connections in this state look fully connected to the clients, but they are
without buffers, thus any data sent to the server will get dropped.
> This won't be a problem for protocols where client first wait for server's greeting.
Even for clients-speak-first protocols, it will be fine if the overload is transient and such
connections are accepted before the retransmission of dropped packets arrive. Otherwise, clients
can hit socket timeout after several retransmissions.  In certain situations, connection will
get reset while clients still waiting for ack.
> We have seen this happening to IPC clients during SASL negotiation. Since no call has
been sent, we should allow retry when connection reset or socket timeout happens in this stage.

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