From: bert hubert <bert.hubert@netherlabs.nl>
Date: Thu, 13 Mar 2014 09:08:54 +0000 (+0100)
Subject: document new bindbackend semantics, plus fix that we did not learn about slave zones.
X-Git-Tag: rec-3.6.0-rc1~138^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d8f47a4a82ff280effc4fc573f039c7de475f31c;p=thirdparty%2Fpdns.git

document new bindbackend semantics, plus fix that we did not learn about slave zones.
---

diff --git a/modules/bindbackend/bindbackend2.cc b/modules/bindbackend/bindbackend2.cc
index f2307cbf33..6c983e6f86 100644
--- a/modules/bindbackend/bindbackend2.cc
+++ b/modules/bindbackend/bindbackend2.cc
@@ -49,13 +49,30 @@
 #include "pdns/lock.hh"
 #include "pdns/namespaces.hh"
 
+/* 
+   All instances of this backend share one s_state, which is indexed by zone name and zone id.
+   The s_state is protected by a read/write lock, and the goal it to only interact with it briefly.
+   When a query comes in, we take a read lock and COPY the best zone to answer from s_state (BB2DomainInfo object)
+   All answers are served from this copy.
+
+   To interact with s_state, use safeGetBBDomainInfo (search on name or id), safePutBBDomainInfo (to update)
+   or safeRemoveBBDomainInfo. These all lock as they should.
+
+   Several functions need to traverse s_state to get data for the rest of PowerDNS. When doing so,
+   you need to manually take the s_state_lock (read).
+
+   Parsing zones happens with parseZone(), which fills a BB2DomainInfo object. This can then be stored with safePutBBDomainInfo.
+
+   Finally, the BB2DomainInfo contains all records as a LookButDontTouch object. This makes sure you only look, but don't touch, since
+   the records might be in use in other places.
+*/
 
 Bind2Backend::state_t Bind2Backend::s_state;
 int Bind2Backend::s_first=1;
 bool Bind2Backend::s_ignore_broken_records=false;
 
 pthread_rwlock_t Bind2Backend::s_state_lock=PTHREAD_RWLOCK_INITIALIZER;
-pthread_mutex_t Bind2Backend::s_supermaster_config_lock=PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t Bind2Backend::s_supermaster_config_lock=PTHREAD_MUTEX_INITIALIZER; // protects writes to config file
 pthread_mutex_t Bind2Backend::s_startup_lock=PTHREAD_MUTEX_INITIALIZER;
 string Bind2Backend::s_binddirectory;  
 
@@ -144,7 +161,6 @@ bool Bind2Backend::safeRemoveBBDomainInfo(const std::string& name)
   return true;
 }
 
-
 void Bind2Backend::safePutBBDomainInfo(const BB2DomainInfo& bbd)
 {
   WriteLock rl(&s_state_lock);
@@ -348,7 +364,7 @@ void Bind2Backend::getUnfreshSlaveInfos(vector<DomainInfo> *unfreshDomains)
     }
     catch(...){}
     sd.serial=soadata.serial;
-    if(sd.last_check+soadata.refresh<(unsigned int)time(0))
+    if(sd.last_check+soadata.refresh < (unsigned int)time(0))
       unfreshDomains->push_back(sd);    
   }
 }
@@ -554,8 +570,7 @@ string Bind2Backend::DLAddDomainHandler(const vector<string>&parts, Utility::pid
   BB2DomainInfo bbd;
   if(safeGetBBDomainInfo(domainname, &bbd))
     return "Already loaded";
-
-  Bind2Backend bb2; // XXX do we need this?
+  Bind2Backend bb2; // createdomainentry needs access to our configuration
   bbd=bb2.createDomainEntry(domainname, filename);
   bbd.d_filename=filename;
   bbd.d_checknow=true;
@@ -772,7 +787,7 @@ void Bind2Backend::loadConfig(string* status)
 
           try {
             parseZoneFile(&bbd);
-	    safePutBBDomainInfo(bbd);
+
           }
           catch(PDNSException &ae) {
             ostringstream msg;
@@ -795,6 +810,7 @@ void Bind2Backend::loadConfig(string* status)
             L<<Logger::Warning<<d_logprefix<<msg.str()<<endl;
             rejected++;
           }
+	  safePutBBDomainInfo(bbd);
         }
       }
 
@@ -1247,8 +1263,6 @@ BB2DomainInfo Bind2Backend::createDomainEntry(const string &domain, const string
   bbd.d_name = domain;
   bbd.setCheckInterval(getArgAsNum("check-interval"));
   bbd.d_filename = filename;
-  
-  safePutBBDomainInfo(bbd);
   return bbd;
 }
 
diff --git a/modules/bindbackend/bindbackend2.hh b/modules/bindbackend/bindbackend2.hh
index cdd257d763..6ceb75e66c 100644
--- a/modules/bindbackend/bindbackend2.hh
+++ b/modules/bindbackend/bindbackend2.hh
@@ -283,7 +283,7 @@ private:
 
   set<string> alsoNotify; //!< this is used to store the also-notify list of interested peers.
 
-  BB2DomainInfo createDomainEntry(const string &domain, const string &filename);
+  BB2DomainInfo createDomainEntry(const string &domain, const string &filename); //!< does not insert in s_state
 
   int d_transaction_id;
   string d_transaction_tmpname;