libpqxx 7.8.1
transactor.hxx
1/* Transactor framework, a wrapper for safely retryable transactions.
2 *
3 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/transactor instead.
4 *
5 * Copyright (c) 2000-2023, Jeroen T. Vermeulen.
6 *
7 * See COPYING for copyright license. If you did not receive a file called
8 * COPYING with this source code, please notify the distributor of this
9 * mistake, or contact the author.
10 */
11#ifndef PQXX_H_TRANSACTOR
12#define PQXX_H_TRANSACTOR
13
14#if !defined(PQXX_HEADER_PRE)
15# error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
16#endif
17
18#include <functional>
19#include <type_traits>
20
21#include "pqxx/connection.hxx"
22#include "pqxx/transaction.hxx"
23
24namespace pqxx
25{
69
71
100template<typename TRANSACTION_CALLBACK>
101inline auto perform(TRANSACTION_CALLBACK &&callback, int attempts = 3)
102 -> std::invoke_result_t<TRANSACTION_CALLBACK>
103{
104 if (attempts <= 0)
105 throw std::invalid_argument{
106 "Zero or negative number of attempts passed to pqxx::perform()."};
107
108 for (; attempts > 0; --attempts)
109 {
110 try
111 {
112 return std::invoke(callback);
113 }
114 catch (in_doubt_error const &)
115 {
116 // Not sure whether transaction went through or not. The last thing in
117 // the world that we should do now is try again!
118 throw;
119 }
120 catch (statement_completion_unknown const &)
121 {
122 // Not sure whether our last statement succeeded. Don't risk running it
123 // again.
124 throw;
125 }
126 catch (protocol_violation const &)
127 {
128 // This is a subclass of broken_connection, but it's not one where
129 // retrying is likely to do us any good.
130 throw;
131 }
132 catch (broken_connection const &)
133 {
134 // Connection failed. May be worth retrying, if the transactor opens its
135 // own connection.
136 if (attempts <= 1)
137 throw;
138 continue;
139 }
140 catch (transaction_rollback const &)
141 {
142 // Some error that may well be transient, such as serialization failure
143 // or deadlock. Worth retrying.
144 if (attempts <= 1)
145 throw;
146 continue;
147 }
148 }
149 throw pqxx::internal_error{"No outcome reached on perform()."};
150}
151} // namespace pqxx
153#endif
The home of all libpqxx classes, functions, templates, etc.
Definition array.hxx:33
auto perform(TRANSACTION_CALLBACK &&callback, int attempts=3) -> std::invoke_result_t< TRANSACTION_CALLBACK >
Simple way to execute a transaction with automatic retry.
Definition transactor.hxx:101
Exception class for lost or failed backend connection.
Definition except.hxx:81
Exception class for micommunication with the server.
Definition except.hxx:103
"Help, I don't know whether transaction was committed successfully!"
Definition except.hxx:165
The backend saw itself forced to roll back the ongoing transaction.
Definition except.hxx:178
We can't tell whether our last statement succeeded.
Definition except.hxx:214
Internal error in libpqxx library.
Definition except.hxx:242