From ec008731813c94a77adb5a33455a4595a682c3e2 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Mon, 10 May 2010 14:09:21 -0700
Subject: [PATCH] make Mysql2::Client destructor safely non-blocking

Since sending a QUIT message to the MySQL server is more of a
formality than a hard requirement in a TCP-based protocol, we'll
just fire-and-forget the message to avoid any chance of blocking
the interpreter during the GC finalizer phase.  Since the socket
will be closed immediately afterwards, there's no long-term
side-effects from making the socket non-blocking.

We do this instead of using rb_thread_blocking_region because
the GVL is already destroyed by the time the ObjectSpace
finalizers are called under 1.9.
---
 ext/mysql2_ext.c | 23 ++++++++++++++++++-----
 ext/mysql2_ext.h |  1 +
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/ext/mysql2_ext.c b/ext/mysql2_ext.c
index 1df155e..254eebc 100644
--- a/ext/mysql2_ext.c
+++ b/ext/mysql2_ext.c
@@ -187,10 +187,23 @@ static void rb_mysql_client_free(void * ptr) {
 
   if (client->client) {
     /*
-     * this may send a "QUIT" message to the server and thus block
-     * on the socket write, users are encouraged to close this manually
-     * to avoid this behavior
+     * we'll send a QUIT message to the server, but that message is more of a
+     * formality than a hard requirement since the socket is getting shutdown
+     * anyways, so ensure the socket write does not block our interpreter
      */
+    int fd = client->client->net.fd;
+    int flags;
+
+    if (fd >= 0) {
+      /*
+       * if the socket is dead we have no chance of blocking,
+       * so ignore any potential fcntl errors since they don't matter
+       */
+      flags = fcntl(fd, F_GETFL);
+      if (flags > 0 && !(flags & O_NONBLOCK))
+        fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+    }
+
     mysql_close(client->client);
   }
   xfree(ptr);
@@ -204,8 +217,8 @@ static VALUE nogvl_close(void * ptr) {
 /*
  * Immediately disconnect from the server, normally the garbage collector
  * will disconnect automatically when a connection is no longer needed.
- * Explicitly closing this can free up server resources sooner and is
- * also 100% safe when faced with signals or running multithreaded
+ * Explicitly closing this will free up server resources sooner than waiting
+ * for the garbage collector.
  */
 static VALUE rb_mysql_client_close(VALUE self) {
   mysql2_client_wrapper *client;
diff --git a/ext/mysql2_ext.h b/ext/mysql2_ext.h
index b02f0dd..668f2b6 100644
--- a/ext/mysql2_ext.h
+++ b/ext/mysql2_ext.h
@@ -1,4 +1,5 @@
 #include <ruby.h>
+#include <fcntl.h>
 
 #ifdef HAVE_MYSQL_H
 #include <mysql.h>