MDEV-18702 mysqldump: add variable 'max-statement-time'bb-10.3-danielblack-MDEV-18702

With a global non-default max-statement-time of a time interval that exceed
the query time mysqldump queries when doing a backup.

To solve both, add a max-statement-time option, defaulting to 0 (unlimited time).

Also like mariabackup, set the session wait_timeout=2147483. The
time/processing between mysqldump times isn't expected to get that
close ever, but let's adopt the standard of mariabackup as no-one has
challenged it has having a detrimental effect.

2 files changed, 46 insertions, 1 deletions

diff --git a/client/mysqldump.c b/client/mysqldump.c
index 6cdc3db3c08..e9da2112e81 100644
--- a/client/mysqldump.c
+++ b/client/mysqldump.c
@@ -145,7 +145,9 @@ static TYPELIB opt_system_types=
 static ulonglong opt_system= 0ULL;
 static my_bool insert_pat_inited= 0, debug_info_flag= 0, debug_check_flag= 0,
                select_field_names_inited= 0;
-static ulong opt_max_allowed_packet, opt_net_buffer_length;
+static ulong opt_max_allowed_packet;
+static double opt_max_statement_time= 0.0;
+static ulong opt_net_buffer_length;
 static MYSQL mysql_connection,*mysql=0;
 static DYNAMIC_STRING insert_pat, select_field_names;
 static char  *opt_password=0,*current_user=0,
@@ -162,6 +164,7 @@ static my_bool server_supports_switching_charsets= TRUE;
 static ulong opt_compatible_mode= 0;
 #define MYSQL_OPT_MASTER_DATA_EFFECTIVE_SQL 1
 #define MYSQL_OPT_MASTER_DATA_COMMENTED_SQL 2
+#define MYSQL_OPT_MAX_STATEMENT_TIME 0
 #define MYSQL_OPT_SLAVE_DATA_EFFECTIVE_SQL 1
 #define MYSQL_OPT_SLAVE_DATA_COMMENTED_SQL 2
 static uint opt_mysql_port= 0, opt_master_data;
@@ -464,6 +467,10 @@ static struct my_option my_long_options[] =
     &opt_max_allowed_packet, &opt_max_allowed_packet, 0,
     GET_ULONG, REQUIRED_ARG, 24*1024*1024, 4096,
    (longlong) 2L*1024L*1024L*1024L, MALLOC_OVERHEAD, 1024, 0},
+  {"max-statement-time", MYSQL_OPT_MAX_STATEMENT_TIME,
+   "Max statement execution time. If unset, overrides server default with 0.",
+   &opt_max_statement_time, &opt_max_statement_time, 0, GET_DOUBLE,
+   REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"net_buffer_length", OPT_NET_BUFFER_LENGTH, 
    "The buffer size for TCP/IP and socket communication.",
     &opt_net_buffer_length, &opt_net_buffer_length, 0,
@@ -6857,6 +6864,14 @@ int main(int argc, char **argv)
   if (!path)
     write_header(md_result_file, *argv);
 
+  /* Set MAX_STATEMENT_TIME to 0 unless set in client */
+  char query[48];
+  my_snprintf(query, sizeof(query), "/*!100100 SET @@MAX_STATEMENT_TIME=%f */", opt_max_statement_time);
+  mysql_query(mysql, query);
+
+  /* Set server side timeout between client commands to server compiled-in default */
+  mysql_query(mysql, "/*!100100 SET WAIT_TIMEOUT=DEFAULT */");
+
   /* Check if the server support multi source */
   if (mysql_get_server_version(mysql) >= 100000)
   {
diff --git a/man/mysqldump.1 b/man/mysqldump.1
index ae6d76f24c3..140bc45c7c6 100644
--- a/man/mysqldump.1
+++ b/man/mysqldump.1
@@ -1361,6 +1361,21 @@ Sets the maximum packet length to send to or receive from server\&.
 .sp -1
 .IP \(bu 2.3
 .\}
+.\" mysqldump: max-statement-time option
+.\" max-statement-time option: mysqldump
+\fB\-\-max\-statement\-time=\fR\fB\fIseconds\fR\fR
+.sp
+Sets the maximum time any statement can run before being timed out by the server. (Default value is 0 (no limit))\&
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
 .\" mysqldump: net-buffer-length option
 .\" net-buffer-length option: mysqldump
 \fB\-\-net\-buffer\-length=\fR\fB\fIlength\fR\fR
@@ -2619,6 +2634,21 @@ The maximum size of the buffer for client/server communication\&. The maximum is
 .sp -1
 .IP \(bu 2.3
 .\}
+max_statement_time
+.sp
+A query that has taken more than max_statement_time seconds will be aborted and the backup will
+fail\&. The argument will be treated as a decimal value with microsecond precision\&. A value
+of 0 (default) means no timeout\&. The maximum timeout is 31536000 seconds\&.
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
 net_buffer_length
 .sp
 The initial size of the buffer for client/server communication\&. When creating multiple\-row