Implemented variable mysql-poll_timeout_on_failure (issue #251)

include/mysql_thread.h

@@ -343,6 +343,7 @@ class Standard_MySQL_Threads_Handler: public MySQL_Threads_Handler
 #endif /* DEBUG */
 		uint16_t server_capabilities;
 		int poll_timeout;
+		int poll_timeout_on_failure;
 	} variables;
 	PtrArray *bind_fds;
 	MySQL_Listeners_Manager *MLM;

include/proxysql_structs.h

@@ -621,6 +621,7 @@ __thread char *mysql_thread___connect_timeout_server_error;
 __thread uint16_t mysql_thread___server_capabilities;
 __thread uint8_t mysql_thread___default_charset;
 __thread int mysql_thread___poll_timeout;
+__thread int mysql_thread___poll_timeout_on_failure;
 __thread bool mysql_thread___have_compress;
 __thread bool mysql_thread___servers_stats;
 #ifdef DEBUG
@@ -641,6 +642,7 @@ extern __thread char *mysql_thread___connect_timeout_server_error;
 extern __thread uint16_t mysql_thread___server_capabilities;
 extern __thread uint8_t mysql_thread___default_charset;
 extern __thread int mysql_thread___poll_timeout;
+extern __thread int mysql_thread___poll_timeout_on_failure;
 extern __thread bool mysql_thread___have_compress;
 extern __thread bool mysql_thread___servers_stats;
 #ifdef DEBUG

lib/MySQL_Session.cpp

@@ -1280,7 +1280,15 @@ void MySQL_Session::handler___client_DSS_QUERY_SENT___server_DSS_NOT_INITIALIZED
 		mybe->server_myds->myconn=MyHGM->get_MyConn_from_pool(mybe->hostgroup_id);
 //	}
 	proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 5, "Sess=%p -- server_myds=%p -- MySQL_Connection %p\n", this, mybe->server_myds,  mybe->server_myds->myconn);
-	if (mybe->server_myds->myconn==NULL) { return; }
+	if (mybe->server_myds->myconn==NULL) {
+		// we couldn't get a connection for whatever reason, ex: no backends, or too busy
+		if (thread->mypolls.poll_timeout==0) { // tune poll timeout
+			if (thread->mypolls.poll_timeout > mysql_thread___poll_timeout_on_failure) {
+				thread->mypolls.poll_timeout = mysql_thread___poll_timeout_on_failure;
+			}
+		}
+		return;
+	}
 	if (mybe->server_myds->myconn->fd==-1) {
 		// we didn't get a valid connection, we need to create one
 		proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 5, "Sess=%p -- MySQL Connection has no FD\n", this);

lib/Standard_MySQL_Thread.cpp

@@ -121,6 +121,7 @@ static char * mysql_thread_variables_names[]= {
 	(char *)"ping_timeout_server",
 	(char *)"default_schema",
 	(char *)"poll_timeout",
+	(char *)"poll_timeout_on_failure",
 	(char *)"server_capabilities",
 	(char *)"server_version",
 	(char *)"servers_stats",
@@ -157,6 +158,7 @@ Standard_MySQL_Threads_Handler::Standard_MySQL_Threads_Handler() {
 	variables.server_version=strdup((char *)"5.1.30");
 	variables.server_capabilities=CLIENT_FOUND_ROWS | CLIENT_PROTOCOL_41 | CLIENT_IGNORE_SIGPIPE | CLIENT_TRANSACTIONS | CLIENT_SECURE_CONNECTION | CLIENT_CONNECT_WITH_DB | CLIENT_SSL;
 	variables.poll_timeout=2000;
+	variables.poll_timeout_on_failure=100;
 	variables.have_compress=true;
 	variables.servers_stats=true;
 #ifdef DEBUG
@@ -261,6 +263,7 @@ int Standard_MySQL_Threads_Handler::get_variable_int(char *name) {
 	if (!strcmp(name,"have_compress")) return (int)variables.have_compress;
 	if (!strcmp(name,"servers_stats")) return (int)variables.servers_stats;
 	if (!strcmp(name,"poll_timeout")) return variables.poll_timeout;
+	if (!strcmp(name,"poll_timeout_on_failure")) return variables.poll_timeout_on_failure;
 	if (!strcmp(name,"stacksize")) return ( stacksize ? stacksize : DEFAULT_STACK_SIZE);
 	proxy_error("Not existing variable: %s\n", name); assert(0);
 	return 0;
@@ -298,6 +301,10 @@ char * Standard_MySQL_Threads_Handler::get_variable(char *name) {	// this is the
 		sprintf(intbuf,"%d",variables.poll_timeout);
 		return strdup(intbuf);
 	}
+	if (!strcmp(name,"poll_timeout_on_failure")) {
+		sprintf(intbuf,"%d",variables.poll_timeout_on_failure);
+		return strdup(intbuf);
+	}
 	if (!strcmp(name,"threads")) {
 		sprintf(intbuf,"%d", (num_threads ? num_threads : DEFAULT_NUM_THREADS));
 		return strdup(intbuf);
@@ -415,6 +422,15 @@ bool Standard_MySQL_Threads_Handler::set_variable(char *name, char *value) {	//
 			return false;
 		}
 	}
+	if (!strcmp(name,"poll_timeout_on_failure")) {
+		int intv=atoi(value);
+		if (intv > 10 && intv < 20000) {
+			variables.poll_timeout_on_failure=intv;
+			return true;
+		} else {
+			return false;
+		}
+	}
 	if (!strcmp(name,"default_charset")) {
 		int intv=atoi(value);
 		if (intv > 0 && intv < 256) {
@@ -977,6 +993,7 @@ void Standard_MySQL_Thread::refresh_variables() {
 	mysql_thread___server_capabilities=GloMTH->get_variable_uint16((char *)"server_capabilities");
 	mysql_thread___default_charset=GloMTH->get_variable_uint8((char *)"default_charset");
 	mysql_thread___poll_timeout=GloMTH->get_variable_int((char *)"poll_timeout");
+	mysql_thread___poll_timeout_on_failure=GloMTH->get_variable_int((char *)"poll_timeout_on_failure");
 	mysql_thread___have_compress=(bool)GloMTH->get_variable_int((char *)"have_compress");
 	mysql_thread___servers_stats=(bool)GloMTH->get_variable_int((char *)"servers_stats");
 #ifdef DEBUG