Re: DNSJava failing to lookup records?

[Andrew H. <aa...@vo...>]

Great!  That's more than enough to go on, and gives me all the 
information I need to work this out.  I think my best bet is simply to 
log certain key pieces of information; if it happens again I'll 
(hopefully) have enough info to track down the problem.

Thanks for the response,

- a.

Brian Wellington wrote:

>On Mon, 20 Oct 2003, Andrew Houghton wrote:
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>>Here at VolunteerMatch we use dnsjava (1.3.3) to do some basic semantic 
>>verification of user email addresses before they're added to our 
>>system.  Users enter an email address for most important site actions, 
>>and we do logical RFC 2822 checks followed by a simple test along the 
>>lines of 'does this domain have an MX record? if not, does it have an A 
>>record?'.
>>
>>On Sunday, after restarting our servlet engine (Jetty 4.2.12 running on 
>>RH Linux 7.3, Sun JDK 1.4.0), every record lookup was returning null.  
>>This has happened once before on a brand new machine, and we chalked it 
>>up to setup problems (we had some problems in our resolv.conf that 
>>needed fixing).  This time around, though, there weren't any changes in 
>>the system to cause the problem.  For the record, using dig to lookup 
>>records from a shell worked fine for the same domains that dnsjava was 
>>failing on.
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>What does Lookup.getErrorString() return for the failed queries?
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>>My first guess was that dnsjava simply had some problems reading or 
>>parsing resolv.conf, and thus the initialization step was booched, but 
>>that doesn't make much sense to me given that on any normal day it 
>>doesn't have this problem.  I'm about to dive into the code to try and 
>>figure out what's going on, but can anyone offhand give any ideas?  Has 
>>anyone seen this problem?
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>I've never heard of any problems with the resolv.conf parser, but it's 
>possible.
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>>And, most importantly, is there a way to force dnsjava to initialize and 
>>return some sort if a status code?  I'm not certain what a status code 
>>would mean in this case, but ideally I'm looking for some way of finding 
>>what dnsjava is using as name servers, how it decided on them, and 
>>whether the initialization process had any problems.
>>    
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>
>Setting the verbose option (-Ddnsjava.options=verbose) will cause the 
>resolv.conf parser, called from the initialization code, to print a 
>message for each server it parses (in the FindServer.addServer() method).  
>There's also the FindServer.servers() static method, which returns the 
>servers being used (or the FindServer.searchPath() method returning the 
>domain search list).  Setting the verbose option will also cause each 
>lookup to log a message, so while useful for debugging, it's probably not 
>something you'd want on all the time.
>
>I'm not sure how much this helps, but it should tell you if there's a 
>problem with initialization or something later.
>
>Brian
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