Chapter 4 MySQL Router Application

There are a number of options available for controlling the application. Each is listed below with a brief explanation.

The --help option has an added benefit. Along with the explanation of each of the options, the --help option also displays the paths used to find the configuration file. The following excerpt of the --help output shows an example from a Ubuntu 15.04 machine.

shell>  mysqlrouter --help

MySQL Router v2.0.3 on Linux (64-bit) (GPL community edition)
Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Start MySQL Router.

Configuration read from the following files in the given order (enclosed
in parentheses means not available for reading):
  /etc/mysqlrouter/mysqlrouter.ini
  (/home/user/.mysqlrouter.ini)
...

The configuration section shows the order for the paths that may be used for reading the configuration file. In this case, only the first file is accessible.

Recall the Router requires a configuration file to setup the routing strategies and to provide paths for its plugins as well as other controls such as logging. Recall also that the Router will search a predetermined list of default paths for some platforms. However, the best way to start the Router is to provide the configuration file with the --config= option. An example follows.

shell>  mysqlrouter --config=/path/to/file/my_router.ini     
2015-10-22 10:51:34 INFO    [7f5f66768700] routing:basic_redirect started: listening on localhost:7001; read-write
2015-10-22 10:51:34 INFO    [7f5f65f67700] routing:read_only_redirect started: listening on localhost:7002; read-only
    

Here we see the Router has started as a console application and has reported its routing strategies. Notice that the Router is listening on two ports and that the name of each routing strategy is listed.

For example, the first strategy is listed as routing:basic_redirect, is listening on port 7001 and its mode is read-write. The corresponding section in the configuration file is shown below.

[routing:basic_redirect]
bind_address = localhost:7001
mode = read-write
destinations = localhost:13001,localhost:13002,localhost:13003

Notice that the name, port, and mode were taken directly from the configuration file. In this way, you can quickly determine which routing strategies are active. This could be particularly handy if you are running several instances of the Router or are using the extra configuration file option.

Similarly, the second strategy is listed as routing:read_only_redirect, is listening on port 7002 and its mode is read-only. The corresponding section in the configuration file is shown below.

[routing:read_only_redirect]
bind_address = localhost:7002
mode = read-only
destinations = localhost:3006,localhost:3307

To stop the Router, issue a CTRL + C in the console or issue a SIGTERMsignal to stop the application. For example, you could issue the following command to send the SIGTERM to the application. Note that we use the .pid file for the application.

shell>  kill -SIGTERM <pid>   

In this case, the <pid> is the process id of the mysqlrouter application.

The logging feature can be handy for developing and testing your application and deployment of the MySQL Router. To use logging, you must turn it on in the configuration file under a section named logging. An example is shown below.

[logger]
level = INFO

By default, all logs are sent to the console. Alternatively, you can optionally store the log in a file. To do so, specify a logging_folder path for the logging file in the DEFAULTS section in the configuration file as shown below. The logging file will be named mysqlrouter.log.

[DEFAULT]
logging_folder = /path/to/folder
plugin_folder = /usr/local/lib/mysqlrouter
config_folder = /etc/mysql
runtime_folder = /var/run

When logging to a file, the console output is suppressed and all messages go to the file except for a reminder notice as shown below. Thus, you can either log messages to the console, which is the default, or specify a logging path in the configuration file to log to a file.

Logging to /path/to/folder/mysqlrouter.log

There are two common logging modes:

The following example shows what the messages would look like for a logging mode of DEBUG. Notice both INFO and DEBUG messages are shown.

2015-10-22 11:21:07 INFO    [7fdd091f8700] routing:read_only_redirect started: listening on localhost:7002; read-only
2015-10-22 11:21:07 INFO    [7fdd119f9700] routing:basic_redirect started: listening on localhost:7001; read-write
2015-10-22 11:27:09 DEBUG   [7fdd0bfff700] Trying server localhost:13001 (index 0)
2015-10-22 11:27:09 DEBUG   [7fdd0bfff700] routing:basic_redirect [127.0.0.1]:49661 - [127.0.0.1]:13001
2015-10-22 11:27:41 DEBUG   [7fdd0bfff700] Routing stopped (up:301b;down:201b) 
2015-10-22 11:28:07 DEBUG   [7fdd0bfff700] Trying server localhost:13001 (index 0)
2015-10-22 11:28:07 DEBUG   [7fdd0bfff700] MySQL Server localhost:13001: Connection refused (111)
2015-10-22 11:28:07 DEBUG   [7fdd0bfff700] Trying server localhost:13002 (index 1)
2015-10-22 11:28:07 DEBUG   [7fdd0bfff700] routing:basic_redirect [127.0.0.1]:49663 - [127.0.0.1]:13002

This example was taken from a log file rather than console output. Notice in the debug statements we see that the routing redirects were recorded. Thus, if you want to see when these occur, you may want to use the DEBUG logging mode.

The next chapter discusses the plugins used with MySQL Router.