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<p class="MsoNormal"><span style="font-size:11.0pt">Hello,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">We use the DNS cache module to reduce the time spent querying DNS records. We recently had a customer call failing and we traced the failure to the customer using an FQDN in the Record-Route header. On the
ACK, OpenSIPS appeared to not be able to resolve the domain even though it had been successfully resolved on the initial request. I found the log for the DNS Cache module and noticed that the value it was inserting was empty:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal" style="line-height:11.25pt;background:white"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">INFO:<span style="background:#FAE9A4">dns_cache</span>:put_dnscache_value: putting key [dnscache_customer.domain.com_a] with
value [] ttl = 60<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">This prompted me to examine all of our logs and I found that the value for these DNS Cache logs is always empty, regardless of the domain. It appears the records are not being serialized properly into the
cache. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The DNS resolution must be succeeding or all of our requests using DNS would be failing, but I have also verified the domains all can be resolved manually on the same box:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">$ nslookup customer.domain.com<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Server: 10.27.0.2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Address: 10.27.0.2#53<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Non-authoritative answer:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Name: customer.domain.com<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Address: 10.27.172.132<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Name: customer.domain.com<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Address: 10.27.192.211<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Name: customer.domain.com<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.5pt;font-family:"Courier New";color:#333333">Address: 10.27.255.53<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Any thoughts? Is there more information I can obtain to determine the cause?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;color:black">Ben Newlin </span>
<o:p></o:p></p>
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