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: dcb_alloc switched malloc to calloc, dcb->fd is initialized to -1. : dcb_process_zombies return value of close(fd) is checked. Closed fds are stored to conn_open array. : dcb_connect assigns new fd only if backend connection succeeds. Dcb is added to poll set in the same way, only if connect succeed. gateway.c : conn_open array is initialized in main. For each created socket, a true is set to corresponding slot. Max. number of slots is 1024. mysql_client_server_protocol.h : gw_do_connect_to declaration mysql_backend.c : gw_create_backend_connection returns rv >= 0 and a protocol which is assigned to backend_dcb. In error, -1 is returned and fd is not set. mysql_client.c : conn_open array is kept up-to-date and protocol pointer is assigned also to dcb outside mysql_protocol_init. mysql_common.c : gw_do_connect_to_backend 3rd argument is pointer to fd, not protocol. dcb is added to poll set later in dcb_connect. skygw_debug.h : define conn_open[1024] array where open connections can be marked in debug build.
/** \mainpage MaxScale by SkySQL The SkySQL MaxScale is an intelligent proxy that allows forwarding of database statements to one or more database server user complex rules and a semantic understanding of the database satements and the roles of the various servers within the backend cluster of databases. The MaxScale is designed to provided load balancing and high avilability functionality transparantly to the applications. In addition it provides a highly scalable and flexibile architecture, with plugin components to support differnt protocols and routing decissions. The MaxScale is implemented in C and makes entensive use of the asynchronous I/O capabilities of the Linux operating system. The epoll system is used to provide the event driven framework for the input and output via sockets. The protocols are implemented as external shared object modules which can be loaded and runtime. These modules support a fixed interface, communicating the entries points via a structure consisting of a set of function pointers. This structured is called the "module object". The code that routes the queries to the database servers is also loaed as external shared objects and are referred to as routing modules. \section Building Building the MaxScale Edit the file build_gateway.inc in your skygateway directory and set the ROOT_PATH and MARIADB_SRC_PATH variables to the location in which you checked out the code and the location of your MariaDB source. Build the libmysqld in $MARIADB_SRC_PATH Go to the sky gateway directory and do a make depend to update all the dependency files and then do a make. This should get you all the things built that you need. Other make targets are available install - Installs the binary and the modules in the location defined by the make variable DEST ctags - Build tags files for the vi editor documentation - Build the doxygen documentation depend - Update the dependencies used by the makefiles Two files are required for the libmysqld library that is used within MaxScale, /usr/local/mysql/share/english/errmsg,sys and a my.cnf file with the following: [mysqld] max_connections=4096 \section Running Running the MaxScale The gateway consists of a core executable and a number of modules that implement the different protocols and routing algorithms. These modules are built as shared objects that are loaded on demand. In order for the gateway to find these modules it will search using a predescribed search path. The rules are: 1. Look in the current directory for the module 2. Look in $MAXSCALE_HOME/modules 3. Look in /usr/local/skysql/MaxScale/modules Configuration is read by default from the file $MAXSCALE_HOME/etc/MaxScale.cnf, /etc/MaxScale.cnf, an example file is included in the root of the source tree. The default location can be overriden by use of the -c flag on the command line. This should be immediately followed by the path to the configuration file. */