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Subject: Re: [wsrp-interop] Java dynamic domain name workaround



it seems that most layer 4 apps don't first check if a machine they want to
contact is reacheable in layer 3.
For instance a telnet foobarbar.com (be carefull, there is a fobar.com host
:-) ) has it's normal layer 4 timeout even if a ping to foobarbar.com would
receive a host unknown icmp message.
It get's even worse if the host exists in the domain name system but is
down. Here we have standard IP timeout...

So from my point of view resolvers should cache IP-Addresses or hostnames
(getAddrByHost) for only a short period of times.
In local networks there should be caching nameservers/forwarders which
should cache the entries and adhere to the standard DNS timeout rules
(expiration, zone serial number changes etc.).
In general I think it is a bad idea for a resolver to cache the entries for
a long time.

Even if an IP-Address is reachable on layer 3 it can mean nothing since -
as Andre said - dynamic addresses are recycled, thus you could contact the
same Address but intend to contact another host.

Mit freundlichen Gruessen / best regards,

        Richard Jacob
______________________________________________________
IBM Lab Boeblingen, Germany
Dept.8288, WebSphere Portal Server Development
Phone: ++49 7031 16-3469  -  Fax: ++49 7031 16-4888
Email: mailto:richard.jacob@de.ibm.com


|---------+---------------------------->
|         |           David Ward       |
|         |           <david.ward@oracl|
|         |           e.com>           |
|         |                            |
|         |           06/24/2003 03:46 |
|         |           PM               |
|---------+---------------------------->
  >--------------------------------------------------------------------------------------------------------------------------------------------------|
  |                                                                                                                                                  |
  |       To:       Rich Thompson/Watson/IBM@IBMUS                                                                                                   |
  |       cc:       wsrp-interop@lists.oasis-open.org                                                                                                |
  |       Subject:  Re: [wsrp-interop] Java dynamic domain name workaround                                                                           |
  >--------------------------------------------------------------------------------------------------------------------------------------------------|




I noticed that the networking layer wasn't immediately failing - it was
just timing out after a very long time. So it might still make sense to
flush before a failure.

Rich Thompson wrote:

      I agree, but usually one can detect the failure to open within the
      networking layer. This reasonably contains where one would instruct
      the resolver to flush any caching for the failed ip address.

      Rich Thompson

                                                                           
   Andre Kramer                                                            
   <andre.kramer@eu.citrix.com         To:        Rich                     
   >                           Thompson/Watson/IBM@IBMUS,                  
                               wsrp-interop@lists.oasis-open.org           
                                       cc:                                 
   06/24/2003 09:01 AM                 Subject:        RE: [wsrp-interop]  
                               Java dynamic domain name workaround         
                                                                           





      IP addresses get recycled or don't provoke ICMP messages, so the
      error can be above the IP (packet) layer.

      regards,
      Andre
      -----Original Message-----
      From: Rich Thompson [mailto:richt2@us.ibm.com]
      Sent: 24 June 2003 13:32
      To: wsrp-interop@lists.oasis-open.org
      Subject: Re: [wsrp-interop] Java dynamic domain name workaround


      Shouldn't this also be reported as a bug? With increasing use of
      dynamic addresses, the resolver should be told to flush the cached
      entry when the IP address is unable to be opened. While this would
      add a small overhead for when static addresses can't be contacted due
      to network problems, it eliminates permanently stranding a dynamic ip
      address.

      Rich Thompson
                                                                          
   David Ward                                                             
   <david.ward@oracle.com>            To:        Richard Jacob            
                               <richard.jacob@de.ibm.com>                 
                                      cc:                                 
   06/23/2003 06:11 PM         wsrp-interop@lists.oasis-open.org          
                                      Subject:        [wsrp-interop] Java 
                               dynamic domain name workaround             
                                                                          






      I just wanted to make sure I hadn't left this as a "loose end".
      Apologies if you have already gathered together this information...

      Richard Jacob wrote:
      Btw. could you report today about that problem and your
      circumvention, so
      we can pass it to the primer editor's?
      The problem was that our Java mid tier, which is in our 'DMZ'
      (Demilitarized Zone?) and doesn't use a proxy, was simply unable to
      contact the IBM service, even though our test environment which ran
      through a proxy worked fine.


      This turned out to be due to the way Java caches IP addresses. The
      java.net.InetAddress class by default caches IP addresses forever
      once it has resolved them once. However, the IBM domain name
      wsrp.dyndns.org actually gets associated with a new IP address every
      24 hours, so this was bound to cause problems for our servlet
      container JVM that stays up forever.


      If we were running on JDK 1.4, it appears we would be able to control
      the "time to live" for cached IP addresses through a security policy.
      However, it seems that the 'private' sun.net.inetaddr.ttl System
      property mentioned in the JDK 1.4 docs also has the same effect on
      JDK 1.3.

      My solution was to edit the config file containing the startup
      options for the servlet container JVM (in Oracle 9iAS this is in
      opmn/conf/opmn.xml) so that the sun.net.inetaddr.ttl property is set
      with a small timeout (I used 120 seconds).


      E.g.


      java -Dsun.net.inetaddr.ttl=120 <normal JVM startup options>


      Regards

      David
      --


|--------------------+---------------------------+-----------------------|
|     David Ward     | Oracle European           |                       |
| Principal Software | Development Centre        |                       |
|      Engineer      | 520 Oracle Parkway        |                 Email:|
|    Oracle Portal   | Thames Valley Park        |                david.w|
|                    | Reading                   |                ard@ora|
|                    | Berkshire RG6 1RA         |                cle.com|
|                    | UK                        |                   Tel:|
|                    |                           |                +44 118|
|                    |                           |                924    |
|                    |                           |                5079   |
|                    |                           |                   Fax:|
|                    |                           |                +44 118|
|                    |                           |                924    |
|                    |                           |                5005   |
|                    |                           |                       |
|--------------------+---------------------------+-----------------------|







--
|--------------------+---------------------------+-----------------------|
|                    |                           |                       |
|     David Ward     |  Oracle European          |                       |
|      Principal     |  Development Centre       |                       |
|  Software Engineer |  520 Oracle Parkway       |                Email: |
|    Oracle Portal   |  Thames Valley Park       |                 david |
|                    |  Reading                  |                 .ward |
|                    |  Berkshire RG6 1RA        |                 @orac |
|                    |  UK                       |                 le.co |
|                    |                           |                 m     |
|                    |                           |                  Tel: |
|                    |                           |                 +44   |
|                    |                           |                 118   |
|                    |                           |                 924   |
|                    |                           |                 5079  |
|                    |                           |                  Fax: |
|                    |                           |                 +44   |
|                    |                           |                 118   |
|                    |                           |                 924   |
|                    |                           |                 5005  |
|                    |                           |                       |
|                    |                           |                       |
|--------------------+---------------------------+-----------------------|








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