pdns_server with GeoIP Backend does not answer

[lvasiliev]

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• Program: Authoritative
• Issue type: Bug report

Short description

We use PowerDNS authoritative with GeoIPBackend and copy every minute via ssh zones.yml and execute pdns_control reload after. Everything works well, but sometimes pdns_server does not responding to DNS queries.

Environment

• Operating system: FreeBSD 12.3-RELEASE
• Software version:

root@geons14:~ # /usr/local/sbin/pdns_server --version
Apr 13 18:08:22 PowerDNS Authoritative Server 4.6.1 (C) 2001-2022 PowerDNS.COM BV
Apr 13 18:08:22 Using 64-bits mode. Built using clang 10.0.1 ([email protected]:llvm/llvm-project.git llvmorg-10.0.1-0-gef32c611aa2) on Apr 10 2022 22:56:11 by root@geons14.
Apr 13 18:08:22 PowerDNS comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it according to the terms of the GPL version 2.
Apr 13 18:08:22 Features: libcrypto-ecdsa libcrypto-ed25519 libcrypto-ed448 libcrypto-eddsa libmaxminddb lua lua-records protobuf curl 
Apr 13 18:08:22 Built-in modules: 
Apr 13 18:08:22 Configured with: " '--disable-static' '--docdir=/usr/local/share/doc/powerdns' '--sysconfdir=/usr/local/etc/pdns' '--with-boost=/usr/local' '--with-dynmodules=pipe bind geoip' '--with-modules=' '--with-libsodium=no' '--disable-ixfrdist' '--without-lmdb' '--without-mysql' '--disable-tools' '--prefix=/usr/local' '--localstatedir=/var' '--mandir=/usr/local/man' '--disable-silent-rules' '--infodir=/usr/local/share/info/' '--build=amd64-portbld-freebsd12.3' 'build_alias=amd64-portbld-freebsd12.3' 'CC=cc' 'CFLAGS=-pipe  -g -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing ' 'LDFLAGS=  -fstack-protector-strong -L/usr/local/lib ' 'LIBS=' 'CPPFLAGS=-isystem /usr/local/include' 'CPP=cpp' 'CXX=c++' 'CXXFLAGS=-pipe -g -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing  -isystem /usr/local/include ' 'PKG_CONFIG=pkgconf'"

• Software source: compiled from FreeBSD ports with debug info

Other information

We got backtrace at that moment:

Executable module set to "/usr/local/sbin/pdns_server".
Architecture set to: x86_64--freebsd12.3.
(lldb) bt
* thread #1, name = 'pdns_server'
  * frame #0: 0x0000000801a998cc libthr.so.3`___lldb_unnamed_symbol192$$libthr.so.3 + 92
    frame #1: 0x0000000801a96e6b libthr.so.3`___lldb_unnamed_symbol161$$libthr.so.3 + 491
    frame #2: 0x0000000801a0f8a2 libc++.so.1`std::__1::condition_variable::wait(std::__1::unique_lock<std::__1::mutex>&) + 18
    frame #3: 0x00000008019cf8eb libc++.so.1`std::__1::__shared_mutex_base::lock_shared() + 91
    frame #4: 0x0000000802b14a35 libgeoipbackend.so`GeoIPBackend::lookup(QType const&, DNSName const&, int, DNSPacket*) [inlined] std::__1::shared_mutex::lock_shared() at shared_mutex:195:70
    frame #5: 0x0000000802b14a29 libgeoipbackend.so`GeoIPBackend::lookup(QType const&, DNSName const&, int, DNSPacket*) [inlined] std::__1::shared_lock<std::__1::shared_mutex>::shared_lock(this=<unavailable>) at shared_mutex:329
    frame #6: 0x0000000802b14a29 libgeoipbackend.so`GeoIPBackend::lookup(QType const&, DNSName const&, int, DNSPacket*) [inlined] ReadLock::ReadLock(this=<unavailable>) at lock.hh:118
    frame #7: 0x0000000802b14a29 libgeoipbackend.so`GeoIPBackend::lookup(QType const&, DNSName const&, int, DNSPacket*) [inlined] ReadLock::ReadLock(this=<unavailable>, lock=<unavailable>) at lock.hh:107
    frame #8: 0x0000000802b14a29 libgeoipbackend.so`GeoIPBackend::lookup(this=0x00000008023d39c0, qtype=0x00007fffffffe3e0, qdomain=0x0000000808abc098, zoneId=-1, pkt_p=0x0000000000000000) at geoipbackend.cc:431                                                                                                                                                                                                                 
    frame #9: 0x000000000127988b pdns_server`DNSBackend::getSOA(this=0x00000008023d39c0, domain=0x0000000808abc098, sd=0x00007fffffffe4b0) at dnsbackend.cc:245:9
    frame #10: 0x0000000802b165bf libgeoipbackend.so`GeoIPBackend::getAllDomains(this=0x00000008023d39c0, domains=<unavailable>, getSerial=<unavailable>, include_disabled=<unavailable>) at geoipbackend.cc:860:11                                                                                                                                                                                                                 
    frame #11: 0x000000000147bea2 pdns_server`UeberBackend::updateZoneCache(this=0x00007fffffffe670) at ueberbackend.cc:287:11
    frame #12: 0x000000000125aa0b pdns_server`mainthread() at common_startup.cc:747:11
    frame #13: 0x0000000001423c3c pdns_server`main(argc=<unavailable>, argv=0x00007fffffffeae8) at receiver.cc:677:5
    frame #14: 0x0000000001204ed2 pdns_server`_start(ap=<unavailable>, cleanup=<unavailable>) at crt1.c:76:7
(lldb) detach
Process 59314 detached

After detach we see in /var/log/messages:

Apr 13 16:08:00 geons14 pdns[59314]: 5001 questions waiting for database/backend attention. Limit is 5000, respawning

[mind04]

Disabling the zone cache is most likely a workaround for your issue.

Related #11416

[lvasiliev]

Thank! We have set the option zone-cache-refresh-interval=0 and are testing again.

[esacs2004]

When I use zone-cache-refresh-interval=0 I'm suddenly unable to query multiple records at all. Debug logs are not helpful. Does anyone know why PDNS would not properly respond to queries after a reload?

[Habbie]

Thank! We have set the option zone-cache-refresh-interval=0 and are testing again.

Given the age of this ticket, I'm going to assume this resolved it, and I will close the ticket.

When I use zone-cache-refresh-interval=0 I'm suddenly unable to query multiple records at all. Debug logs are not helpful. Does anyone know why PDNS would not properly respond to queries after a reload?

If you still have this problem, please open a thread in Discussions, thanks!