Table of Contents
This chapter describes a lot of things that you need to know when
working on the MySQL code. If you plan to contribute to MySQL
development, want to have access to the bleeding-edge versions of
the code, or just want to keep track of development, follow the
instructions in Section 2.9.3, “Installing from the Development Source Tree”. If you
are interested in MySQL internals, you should also subscribe to
our internals mailing list. This list has
relatively low traffic. For details on how to subscribe, please
see Section 1.7.1, “MySQL Mailing Lists”. All developers at MySQL AB
are on the internals list and we help other
people who are working on the MySQL code. Feel free to use this
list both to ask questions about the code and to send patches that
you would like to contribute to the MySQL project!
The MySQL server creates the following threads:
-
One thread manages TCP/IP file connection requests and creates a new dedicated thread to handle the authentication and SQL statement processing for each connection. (On Unix, this thread also manages Unix socket file connection requests.) On Windows, a similar thread manages shared-memory connection requests, and on Windows NT-based systems, a thread manages named-pipe connection requests. Every client connection has its own thread, although the manager threads try to avoid creating threads by consulting the thread cache first to see whether a cached thread can be used for a new connection.
-
On Windows NT, there is a named pipe handler thread that does the same work as the TCP/IP connection thread on named pipe connect requests.
-
On a master replication server, slave server connections are like client connections: There is one thread per connected slave.
-
On a slave replication server, an I/O thread is started to connect to the master server and read updates from it. An SQL thread is started to apply updates read from the master. These two threads run independently and can be started and stopped independently.
-
The signal thread handles all signals. This thread also normally handles alarms and calls
process_alarm()to force timeouts on connections that have been idle too long. -
If mysqld is compiled with
-DUSE_ALARM_THREAD, a dedicated thread that handles alarms is created. This is only used on some systems where there are problems withsigwait()or if you want to use thethr_alarm()code in your application without a dedicated signal handling thread. -
If the server is started with the
--flush_time=valoption, a dedicated thread is created to flush all tables everyvalseconds. -
Each table for which
INSERT DELAYEDstatements are issued gets its own thread.
mysqladmin processlist only shows the
connection, INSERT DELAYED, and replication
threads.
The test system that is included in Unix source and binary distributions makes it possible for users and developers to perform regression tests on the MySQL code. These tests can be run on Unix.
The current set of test cases doesn't test everything in MySQL, but it should catch most obvious bugs in the SQL processing code, operating system or library issues, and is quite thorough in testing replication. Our goal is to have the tests cover 100% of the code. We welcome contributions to our test suite. You may especially want to contribute tests that examine the functionality critical to your system because this ensures that all future MySQL releases work well with your applications.
The test system consists of a test language interpreter
(mysqltest), a shell script to run all tests
(mysql-test-run), the actual test cases
written in a special test language, and their expected results.
To run the test suite on your system after a build, type
make test from the source root directory, or
change location to the mysql-test directory
and type ./mysql-test-run. If you have
installed a binary distribution, change location to the
mysql-test directory under the installation
root directory (for example,
/usr/local/mysql/mysql-test), and run
./mysql-test-run. All tests should succeed.
If any do not, you should try to find out why and report the
problem if it indicates a bug in MySQL. See
Section 1.8, “How to Report Bugs or Problems”.
If one test fails, you should run
mysql-test-run with the
--force option to check whether any other tests
fail.
If you have a copy of mysqld running on the
machine where you want to run the test suite, you do not have to
stop it, as long as it is not using ports
9306 or 9307. If either of
those ports is taken, you should edit
mysql-test-run and change the values of the
master or slave port to one that is available.
In the mysql-test directory, you can run an
individual test case with ./mysql-test-run
test_name.
You can use the mysqltest language to write your own test cases. This is documented in the MySQL Test Framework manual, available at http://dev.mysql.com/doc/.
If you have a question about the test suite, or have a test case
to contribute, send an email message to the MySQL
internals mailing list. See
Section 1.7.1, “MySQL Mailing Lists”. This list does not accept
attachments, so you should FTP all the relevant files to:
ftp://ftp.mysql.com/pub/mysql/upload/