libpqxx 7.7.4
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) 2000-2022, 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 (broken_connection const &)
127 {
128 // Connection failed. May be worth retrying, if the transactor opens its
129 // own connection.
130 if (attempts <= 1)
131 throw;
132 continue;
133 }
134 catch (transaction_rollback const &)
135 {
136 // Some error that may well be transient, such as serialization failure
137 // or deadlock. Worth retrying.
138 if (attempts <= 1)
139 throw;
140 continue;
141 }
142 }
143 throw pqxx::internal_error{"No outcome reached on perform()."};
144}
145} // namespace pqxx
147#endif
The home of all libpqxx classes, functions, templates, etc.
Definition: array.hxx:27
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:69
"Help, I don't know whether transaction was committed successfully!"
Definition: except.hxx:116
The backend saw itself forced to roll back the ongoing transaction.
Definition: except.hxx:123
We can't tell whether our last statement succeeded.
Definition: except.hxx:149
Internal error in libpqxx library.
Definition: except.hxx:167