MWL#192: Non-blocking client API for libmysqlclient.

All client functions that can block on I/O have alternate _start() and
_cont() versions that do not block but return control back to the
application, which can then issue I/O wait in its own fashion and later
call back into the library to continue the operation.

Works behind the scenes by spawning a co-routine/fiber to run the
blocking operation and suspend it while waiting for I/O. This
co-routine/fiber use is invisible to applications.

For i368/x86_64 on GCC, uses very fast assembler co-routine support. On
Windows uses native Win32 Fibers. Falls back to POSIX ucontext on other
platforms. Assembler routines for more platforms are relatively easy to
add by extending mysys/my_context.c, eg. similar to the Lua lcoco
library.

For testing, mysqltest and mysql_client_test are extended with the
option --non-blocking-api. This causes the programs to use the
non-blocking API for database access. mysql-test-run.pl has a similar
option --non-blocking-api that uses this, as well as additional
testcases.

An example program tests/async_queries.c is included that uses the new
non-blocking API with libevent to show how, in a single-threaded
program, to issue many queries in parallel against a database.


client/async_example.c:
  Fix const warning
  ******
  Fix bug with wrong timeout value for poll().
include/Makefile.am:
  Fix missing include for `make dist`
include/mysql.h:
  Add prototypes for all non-blocking API calls.
include/mysql.h.pp:
  Add prototypes for all non-blocking API calls.
mysys/my_context.c:
  Fix type warning for makecontext() function pointer argument.
sql-common/mysql_async.c:
  Fix crashes in the non-blocking API for functions that can take MYSQL argument
  that is NULL.
tests/Makefile.am:
  Add header file to `make dist`
tests/mysql_client_test.c:
  Replace blocking calls with wrappers around the non-blocking calls, used in
  mysql_client_test to test the new non-blocking API.
tests/nonblock-wrappers.h:
  Replace blocking calls with wrappers around the non-blocking calls, used in
  mysql_client_test to test the new non-blocking API.

1 files changed, 11 insertions, 0 deletions

diff --git a/include/sql_common.h b/include/sql_common.h
index 6b66ae2fd81..8bb33e3779c 100644
--- a/include/sql_common.h
+++ b/include/sql_common.h
@@ -26,11 +26,18 @@ extern const char	*unknown_sqlstate;
 extern const char	*cant_connect_sqlstate;
 extern const char	*not_error_sqlstate;
 
+
+struct mysql_async_context;
+
 struct st_mysql_options_extention {
   char *plugin_dir;
   char *default_auth;
 };
 
+struct st_mysql_extension {
+  struct mysql_async_context *async_context;
+};
+
 typedef struct st_mysql_methods
 {
   my_bool (*read_query_result)(MYSQL *mysql);
@@ -102,6 +109,10 @@ void mysql_client_plugin_deinit();
 struct st_mysql_client_plugin;
 extern struct st_mysql_client_plugin *mysql_client_builtins[];
 
+/* Non-blocking client API. */
+void my_context_install_suspend_resume_hook(struct mysql_async_context *b,
+                                            void (*)(my_bool, void *), void *);
+
 #ifdef	__cplusplus
 }
 #endif