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, 4 insertions, 0 deletions

diff --git a/.bzrignore b/.bzrignore
index 6b18d09723b..cd92df693fc 100644
--- a/.bzrignore
+++ b/.bzrignore
@@ -350,6 +350,7 @@ client/ssl_test
 client/thimble
 client/thread_test
 client/tmp.diff
+client/async_example
 client_debug/*
 client_release/*
 client_test
@@ -681,6 +682,7 @@ libmysqld/unireg.cc
 libmysqld/discover_xt.cc
 libmysqld/ha_pbxt.cc
 libmysqld/myxt_xt.cc
+libmysqld/mysql_async.c
 libmysqltest/*.ds?
 libmysqltest/*.vcproj
 libmysqltest/mytest.c
@@ -1867,6 +1869,7 @@ tests/bug25714
 tests/client_test
 tests/connect_test
 tests/mysql_client_test
+tests/async_queries
 thr_insert_test/*
 thr_test/*
 thread_test
@@ -1952,6 +1955,7 @@ client/sql_list.cc
 client/sql_list.h
 libmysqld/client_plugin.c
 sql/client_plugin.c
+sql/mysql_async.c
 *.dgcov
 libmysqld/create_options.cc
 storage/pbxt/bin/xtstat