adding MySQL.WaitTimeout

Summary:
so a connection can wait for longer time before going away.

Test Plan:
entity/questions

DiffCamp Revision: 125818
Reviewed By: mwilliams
CC: hphp-diffs@lists, sgrimm, mwilliams
Revert Plan:
OK

doc/options.compiled

@@ -648,6 +648,7 @@ users can use the same machine serving their own source files.
     Localize = false           # true for native driver that's faster
     ConnectTimeout = 1000      # in ms
     ReadTimeout = 1000         # in ms
+    WaitTimeout = -1           # in ms, -1 means "don't set"
     SlowQueryThreshold = 1000  # in ms, log slow queries as errors
     KillOnTimeout = false
   }

src/runtime/base/runtime_option.cpp

@@ -160,6 +160,7 @@ bool RuntimeOption::MySQLReadOnly = false;
 bool RuntimeOption::MySQLLocalize = false;
 int RuntimeOption::MySQLConnectTimeout = 1000;
 int RuntimeOption::MySQLReadTimeout = 1000;
+int RuntimeOption::MySQLWaitTimeout = -1;
 int RuntimeOption::MySQLSlowQueryThreshold = 1000; // ms
 bool RuntimeOption::MySQLKillOnTimeout = false;
 
@@ -674,6 +675,7 @@ void RuntimeOption::Load(Hdf &config) {
     MySQLLocalize = mysql["Localize"].getBool();
     MySQLConnectTimeout = mysql["ConnectTimeout"].getInt32(1000);
     MySQLReadTimeout = mysql["ReadTimeout"].getInt32(1000);
+    MySQLWaitTimeout = mysql["WaitTimeout"].getInt32(-1);
     MySQLSlowQueryThreshold = mysql["SlowQueryThreshold"].getInt32(1000);
     MySQLKillOnTimeout = mysql["KillOnTimeout"].getBool();
   }

src/runtime/base/runtime_option.h

@@ -158,6 +158,7 @@ class RuntimeOption {
   static bool MySQLLocalize;  // whether to localize MySQL query results
   static int  MySQLConnectTimeout;
   static int  MySQLReadTimeout;
+  static int  MySQLWaitTimeout;
   static int  MySQLSlowQueryThreshold;
   static bool MySQLKillOnTimeout;
 

src/runtime/ext/ext_mysql.cpp

@@ -270,10 +270,19 @@ bool MySQL::connect(CStrRef host, int port, CStrRef socket, CStrRef username,
   }
   IOStatusHelper io("mysql::connect", host.data(), port);
   m_xaction_count = 0;
-  return mysql_real_connect(m_conn, host.data(), username.data(),
-                            password.data(), NULL, port,
-                            socket.empty() ? NULL : socket.data(),
-                            client_flags);
+  bool ret = mysql_real_connect(m_conn, host.data(), username.data(),
+                                password.data(), NULL, port,
+                                socket.empty() ? NULL : socket.data(),
+                                client_flags);
+  if (ret && RuntimeOption::MySQLWaitTimeout > 0) {
+    String query("set session wait_timeout=");
+    query += String((int64)(RuntimeOption::MySQLWaitTimeout / 1000));
+    if (mysql_real_query(m_conn, query.data(), query.size())) {
+      raise_notice("MySQL::connect: failed setting session wait timeout: %s",
+                   mysql_error(m_conn));
+    }
+  }
+  return ret;
 }
 
 bool MySQL::reconnect(CStrRef host, int port, CStrRef socket, CStrRef username,