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, 13 insertions, 2 deletions

diff --git a/vio/viossl.c b/vio/viossl.c
index 61e4d9406a7..58e4089fcd8 100644
--- a/vio/viossl.c
+++ b/vio/viossl.c
@@ -21,6 +21,7 @@
 */
 
 #include "vio_priv.h"
+#include "my_context.h"
 
 #ifdef HAVE_OPENSSL
 
@@ -90,11 +91,16 @@ report_errors(SSL* ssl)
 size_t vio_ssl_read(Vio *vio, uchar* buf, size_t size)
 {
   size_t r;
+  extern int my_ssl_read_async(struct mysql_async_context *b, SSL *ssl,
+                               void *buf, int size);
   DBUG_ENTER("vio_ssl_read");
   DBUG_PRINT("enter", ("sd: %d  buf: 0x%lx  size: %u  ssl: 0x%lx",
 		       vio->sd, (long) buf, (uint) size, (long) vio->ssl_arg));
 
-  r= SSL_read((SSL*) vio->ssl_arg, buf, size);
+  if (vio->async_context && vio->async_context->active)
+    r= my_ssl_read_async(vio->async_context, (SSL *)vio->ssl_arg, buf, size);
+  else
+    r= SSL_read((SSL*) vio->ssl_arg, buf, size);
 #ifndef DBUG_OFF
   if (r == (size_t) -1)
     report_errors((SSL*) vio->ssl_arg);
@@ -107,11 +113,16 @@ size_t vio_ssl_read(Vio *vio, uchar* buf, size_t size)
 size_t vio_ssl_write(Vio *vio, const uchar* buf, size_t size)
 {
   size_t r;
+  extern int my_ssl_write_async(struct mysql_async_context *b, SSL *ssl,
+                                const void *buf, int size);
   DBUG_ENTER("vio_ssl_write");
   DBUG_PRINT("enter", ("sd: %d  buf: 0x%lx  size: %u", vio->sd,
                        (long) buf, (uint) size));
 
-  r= SSL_write((SSL*) vio->ssl_arg, buf, size);
+  if (vio->async_context && vio->async_context->active)
+    r= my_ssl_write_async(vio->async_context, (SSL *)vio->ssl_arg, buf, size);
+  else
+    r= SSL_write((SSL*) vio->ssl_arg, buf, size);
 #ifndef DBUG_OFF
   if (r == (size_t) -1)
     report_errors((SSL*) vio->ssl_arg);