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.

mysql-test/mysql-test-run.pl

@@ -185,6 +185,7 @@ my $opt_ps_protocol;
 my $opt_sp_protocol;
 my $opt_cursor_protocol;
 my $opt_view_protocol;
+my $opt_non_blocking_api;
 
 our $opt_debug;
 our $opt_debug_server;
@@ -964,6 +965,7 @@ sub command_line_setup {
              'sp-protocol'              => \$opt_sp_protocol,
              'view-protocol'            => \$opt_view_protocol,
              'cursor-protocol'          => \$opt_cursor_protocol,
+             'non-blocking-api'         => \$opt_non_blocking_api,
              'ssl|with-openssl'         => \$opt_ssl,
              'skip-ssl'                 => \$opt_skip_ssl,
              'compress'                 => \$opt_compress,
@@ -5468,6 +5470,11 @@ sub start_mysqltest ($) {
     mtr_add_arg($args, "--cursor-protocol");
   }
 
+  if ( $opt_non_blocking_api )
+  {
+    mtr_add_arg($args, "--non-blocking-api");
+  }
+
   if ( $opt_strace_client )
   {
     $exe=  $opt_strace_client || "strace";
@@ -5915,6 +5922,7 @@ Options to control what engine/variation to run
                         (implies --ps-protocol)
   view-protocol         Create a view to execute all non updating queries
   sp-protocol           Create a stored procedure to execute all queries
+  non-blocking-api      Use the non-blocking client API
   compress              Use the compressed protocol between client and server
   ssl                   Use ssl protocol between client and server
   skip-ssl              Dont start server with support for ssl connections

mysql-test/r/mysql_client_test_nonblock.result

@@ -0,0 +1,5 @@
+SET @old_general_log= @@global.general_log;
+SET @old_slow_query_log= @@global.slow_query_log;
+ok
+SET @@global.general_log= @old_general_log;
+SET @@global.slow_query_log= @old_slow_query_log;

mysql-test/r/non_blocking_api.result

@@ -0,0 +1,9 @@
+CREATE TABLE t1 (a INT PRIMARY KEY);
+INSERT INTO t1 VALUES (1);
+SELECT * FROM t1;
+a
+1
+SELECT * FROM t1;
+a
+1
+DROP TABLE t1;

mysql-test/t/mysql_client_test_nonblock-master.opt

@@ -0,0 +1 @@
+--log=$MYSQLTEST_VARDIR/log/master.log --log-output=FILE,TABLE

mysql-test/t/mysql_client_test_nonblock.test

@@ -0,0 +1,23 @@
+# This runs the mysql_client_test using the non-blocking API.
+
+# This test should work in embedded server after we fix mysqltest
+-- source include/not_embedded.inc
+
+SET @old_general_log= @@global.general_log;
+SET @old_slow_query_log= @@global.slow_query_log;
+
+# We run with different binaries for normal and --embedded-server
+#
+# If this test fails with "command "$MYSQL_CLIENT_TEST" failed",
+# you should either run mysql_client_test separartely against a running
+# server or run mysql-test-run --debug mysql_client_test and check
+# var/log/mysql_client_test.trace
+
+--exec echo "$MYSQL_CLIENT_TEST --non-blocking-api" > $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1
+--exec $MYSQL_CLIENT_TEST --non-blocking-api --getopt-ll-test=25600M >> $MYSQLTEST_VARDIR/log/mysql_client_test.out.log 2>&1
+
+# End of 4.1 tests
+echo ok;
+
+SET @@global.general_log= @old_general_log;
+SET @@global.slow_query_log= @old_slow_query_log;

mysql-test/t/named_pipe.test

@@ -2,6 +2,8 @@
 # in order  to optimize things we skip this test on all
 # other platforms
 --source include/windows.inc
+# Named pipe does not support the non-blocking API.
+--disable_non_blocking_api
 
 # Only run this test if named pipe is avaliable
 let $nmp= query_get_value("SHOW VARIABLES LIKE 'named_pipe'", Value, 1);

mysql-test/t/non_blocking_api.test

@@ -0,0 +1,18 @@
+# Test mixing the use of blocking and non-blocking API in a single connection.
+
+--enable_non_blocking_api
+connect (con_nonblock,localhost,root,,test);
+--disable_non_blocking_api
+connect (con_normal,localhost,root,,test);
+
+connection con_nonblock;
+CREATE TABLE t1 (a INT PRIMARY KEY);
+--enable_non_blocking_api
+INSERT INTO t1 VALUES (1);
+--disable_non_blocking_api
+SELECT * FROM t1;
+--enable_non_blocking_api
+SELECT * FROM t1;
+
+connection con_normal;
+DROP TABLE t1;