libpqxx 4.0
transactor.hxx
00001 /*-------------------------------------------------------------------------
00002  *
00003  *   FILE
00004  *      pqxx/transactor.hxx
00005  *
00006  *   DESCRIPTION
00007  *      definition of the pqxx::transactor class.
00008  *   pqxx::transactor is a framework-style wrapper for safe transactions
00009  *   DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/transactor instead.
00010  *
00011  * Copyright (c) 2001-2008, Jeroen T. Vermeulen <jtv@xs4all.nl>
00012  *
00013  * See COPYING for copyright license.  If you did not receive a file called
00014  * COPYING with this source code, please notify the distributor of this mistake,
00015  * or contact the author.
00016  *
00017  *-------------------------------------------------------------------------
00018  */
00019 #ifndef PQXX_H_TRANSACTOR
00020 #define PQXX_H_TRANSACTOR
00021 
00022 #include "pqxx/compiler-public.hxx"
00023 #include "pqxx/compiler-internal-pre.hxx"
00024 
00025 #include "pqxx/connection_base"
00026 #include "pqxx/transaction"
00027 
00028 
00029 /* Methods tested in eg. self-test program test001 are marked with "//[t1]"
00030  */
00031 
00032 namespace pqxx
00033 {
00034 
00036 
00065 template<typename TRANSACTION=transaction<read_committed> >
00066   class transactor :
00067     public PGSTD::unary_function<TRANSACTION, void>
00068 {
00069 public:
00070   explicit transactor(const PGSTD::string &TName="transactor") :        //[t4]
00071     m_Name(TName) { }
00072 
00074 
00085   void operator()(TRANSACTION &T);                                      //[t4]
00086 
00087   // Overridable member functions, called by connection_base::perform() if an
00088   // attempt to run transaction fails/succeeds, respectively, or if the
00089   // connection is lost at just the wrong moment, goes into an indeterminate
00090   // state.  Use these to patch up runtime state to match events, if needed, or
00091   // to report failure conditions.
00092 
00094 
00102   void on_abort(const char[]) throw () {}                               //[t13]
00103 
00105 
00109   void on_commit() {}                                                   //[t7]
00110 
00112 
00123   void on_doubt() throw () {}                                           //[t13]
00124 
00125   // TODO: Rename Name()--is there a compatible way?
00127   PGSTD::string Name() const { return m_Name; }                         //[t13]
00128 
00129 private:
00130   PGSTD::string m_Name;
00131 };
00132 
00133 
00134 }
00135 
00136 
00137 template<typename TRANSACTOR>
00138 inline void pqxx::connection_base::perform(const TRANSACTOR &T,
00139                                            int Attempts)
00140 {
00141   if (Attempts <= 0) return;
00142 
00143   bool Done = false;
00144 
00145   // Make attempts to perform T
00146   // TODO: Differentiate between db-related exceptions and other exceptions?
00147   do
00148   {
00149     --Attempts;
00150 
00151     // Work on a copy of T2 so we can restore the starting situation if need be
00152     TRANSACTOR T2(T);
00153     try
00154     {
00155       typename TRANSACTOR::argument_type X(*this, T2.Name());
00156       T2(X);
00157       X.commit();
00158       Done = true;
00159     }
00160     catch (const in_doubt_error &)
00161     {
00162       // Not sure whether transaction went through or not.  The last thing in
00163       // the world that we should do now is retry.
00164       T2.on_doubt();
00165       throw;
00166     }
00167     catch (const PGSTD::exception &e)
00168     {
00169       // Could be any kind of error.
00170       T2.on_abort(e.what());
00171       if (Attempts <= 0) throw;
00172       continue;
00173     }
00174     catch (...)
00175     {
00176       // Don't try to forge ahead if we don't even know what happened
00177       T2.on_abort("Unknown exception");
00178       throw;
00179     }
00180 
00181     T2.on_commit();
00182   } while (!Done);
00183 }
00184 
00185 
00186 #include "pqxx/compiler-internal-post.hxx"
00187 
00188 #endif
00189