MySQL Database Usage & Administration PHẦN 10 pps

PART II Chapter 13: Replicating Data 313 Ti p Don’t assume everything is fine because you issued the START SLAVE command successfully—monitor the slave’s activities by using the SHOW SLAVE STATUS command. You can also read the slave’s error log to make sure everything is okay. Checking Replication Status The SHOW SLAVE STATUS command provides information about the slave server’s status. It should be run on the slave database server. Here’s what it looks like: (Slave server) mysql> SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: cerberus Master_User: db1-slave Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 106 Relay_Log_File: ACHILLES-relay-bin.000006 Relay_Log_Pos: 251 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Parameter What It Means MASTER_HOST Host name for the master server MASTER_USER Slave name to use when connecting to the master MASTER_PASSWORD Slave’s password to connection to master MASTER_PORT Port number to connect to master MASTER_LOG_FILE Name of master’s binary log file from which to start reading when replication begins MASTER_LOG_POS Position in the master’s binary log file from which to start reading when replication begins MASTER_CONNECT_RETRY Number of seconds to wait between connection attempts RELAY_LOG_FILE Name of the slave relay log from which to begin execution when replication begins RELAY_LOG_POS Position in slave relay log from which to begin execution when replication begins MASTER_SSL Whether to connect to the master server using SSL Ta b l e 13-1 Common Options for the CHANGE MASTER TO Command 314 Part II: Administration Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 106 Relay_Log_Space: 554 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 1 row in set (0.00 sec) In addition to displaying information on the current server and user credentials, the SHOW SLAVE STATUS command provides information on how many times the slave server will attempt to connect to the master server, the status of slave I/O and SQL threads, the name and position in the master’s binary log, the name and position in the slave’s relay log, the size of relay log files, the databases and tables excluded from replication, and whether SSL connections are in use. The SHOW PROCESSLIST command displays information about the threads on the server, and was discussed in Chapter 10. In a replication context, it can be used to obtain status information on both the master and the slave. For each thread, the output is shown in various fields, as illustrated: (Master server) mysql> SHOW PROCESSLIST\G *************************** 1. row *************************** Id: 2 User: db1-slave Host: ACHILLES:43424 db: NULL Command: Binlog Dump Time: 2128 State: Has sent all binlog to slave; waiting for binlog to be updated Info: NULL *************************** 2. row *************************** Id: 6 User: root Host: localhost:1302 db: NULL Command: Query Time: 0 State: NULL Info: show processlist 2 rows in set (0.00 sec) PART II Chapter 13: Replicating Data 315 (Slave server) mysql> SHOW PROCESSLIST\G *************************** 1. row *************************** Id: 12 User: root Host: localhost:43422 db: NULL Command: Sleep Time: 1937 State: Info: NULL *************************** 2. row *************************** Id: 13 User: system user Host: db: NULL Command: Connect Time: 1941 State: Waiting for master to send event Info: NULL *************************** 3. row *************************** Id: 14 User: system user Host: db: NULL Command: Connect Time: 1941 State: Has read all relay log; waiting for the slave I/O thread to update it Info: NULL *************************** 4. row *************************** Id: 16 User: root Host: CERBERUS:1294 db: NULL Command: Query Time: 0 State: NULL Info: SHOW PROCESSLIST 4 rows in set (0.03 sec) Of these various fields, the one you’ll usually be most interested in is the State field, which contains information about what the server is doing. For example, on the master server, you could see something like ‘Sending binlog event to slave.’ On the slave’s I/O thread, you might see ‘Connecting to master’ or ‘Requesting binlog dump.’ On the slave’s SQL thread, a common state is ‘Reading event from the relay log.’ You’ll also find information (where appropriate) about which database the thread is accessing, the statement it’s currently executing, and how long (in seconds) the thread has been executing. 316 Part II: Administration Working with Master Server Binary Logs As discussed earlier, when replicating, everything is based on the binary log on the master server. To display events in this log, the SHOW BINLOG EVENTS command can be used. Here’s an example: (Master server) mysql> SHOW BINLOG EVENTS FROM 4 LIMIT 0,10\G *************************** 1. row *************************** Log_name: mysql-bin.000001 Pos: 4 Event_type: Format_desc Server_id: 10 End_log_pos: 106 Info: Server ver: 5.1.30-community-log, Binlog ver: 4 *************************** 2. row *************************** Log_name: mysql-bin.000001 Pos: 106 Event_type: Query Server_id: 10 End_log_pos: 203 Info: use `db1`; delete from log where RecordID = 37 2 rows in set (0.00 sec) By itself, this command displays all events in the binary log. This can be a time- consuming process when dealing with large binary logs. Therefore, the MySQL manual suggests limiting the output of this command by only showing events starting from a specific position in the log (the FROM clause) and displaying a specified number of events (the LIMIT clause), as in the previous example. The PURGE MASTER command deletes all binary logs on the master server prior to a specified date or log number. As an example, suppose you want to purge all the master binary update logs prior to the one named bin_log.999. You would execute the following: (Master server) mysql> PURGE MASTER LOGS TO mysql-bin.000999; Query OK, 0 rows affected (0.00 sec) Note that this statement requires the SUPER privilege. For additional information about the master server’s binary logs, use the SHOW MASTER STATUS command, which displays the current binary log name and position being written to. Here’s an example: (Master server) mysql> SHOW MASTER STATUS\G *************************** 1. row *************************** File: mysql-bin.000004 Position: 106 Binlog_Do_DB: Binlog_Ignore_DB: 1 row in set (0.00 sec) PART II Chapter 13: Replicating Data 317 Summary This chapter introduced many of the basic replication concepts, such as the master-slave relationship, binary logging, and relay logging. It reviewed and analyzed the three threads that carry out replication on the master and slave servers, and provided step-by- step instructions for taking two servers and configuring them for ongoing replication in two different configurations. Finally, it looked at various SQL commands that are useful for configuring and troubleshooting replication, and that provide considerable information about the processes involved. To learn more about the topics discussed in this chapter, consider visiting the following links: A comparison of replication methods, at http://dev.mysql.com/doc/refman/5.1/• en/replication-sbr-rbr.html Replication variables and options, at http://dev.mysql.com/doc/refman/5.1/• en/replication-options.html Replication thread states, at http://dev.mysql.com/doc/refman/5.1/en/• master-thread-states.html Replication tips, at http://dev.mysql.com/doc/refman/5.1/en/replication-notes • .html This page intentionally left blank APPENDIX Installing MySQL and the Sample Database 320 Part II: Administration T his book discusses the MySQL RDBMS and the tools and commands it provides to store, manipulate, and retrieve data in databases. In case you’re new to MySQL and don’t already have a working installation of the software, this appendix guides you through the process of obtaining, installing, configuring, and testing the MySQL server. It discusses the different versions of MySQL, covers installation of binary versions on both UNIX and Microsoft Windows, and helps create a server environment suitable for running the code examples in this book. Ca u t i o n This appendix is intended to provide an overview and general guide to the process of installing and configuring MySQL on UNIX and Windows. It is not intended as a replacement for the installation instructions that ship with MySQL. If you encounter difficulties installing or configuring MySQL, visit the online MySQL manual or search the Web for detailed troubleshooting information and advice (some links are provided at the end of this chapter). Obtaining MySQL The first order of business is to drop by the official MySQL website at www.mysql.com and get a copy of the most current release of the software. This isn’t necessarily as easy as it sounds—like ice-cream, MySQL comes in many flavors, and you’ll need to select the one that’s most appropriate for your needs. There are two primary decisions to be made when selecting which MySQL distribution to download and use. Choosing which version to install• Choosing between binary and source distributions • Choosing Which Version to Install Sun Microsystems currently makes two versions of the MySQL database server available on their website. MySQL Community Server• This is the General Public License (GPL) version of the MySQL database server, which includes support for both regular, nontransactional storage engines and transaction-safe tables. It is suited for production environments requiring a stable, flexible, and robust database engine, and can be downloaded free of charge. MySQL Enterprise Server• This version is only available as part of the MySQL Enterprise platform, a commercial offering aimed at enterprise customers with business-critical applications. It includes all the features of the Community Server, along with automated updates and hot fixes, consulting support, and monitoring services. So long as you’re willing to put in the time and effort needed to manage the MySQL database server and don’t mind resolving technical issues yourself, the PART II Appendix: Installing MySQL and the Sample Database 321 MySQL Community Server is the most appropriate choice. It’s the version used in all the examples in this book, and it’s stable, feature-rich, and suited for most common applications. However, business customers who need automated updates, continuous system monitoring, and access to 24/7 technical and consulting support would probably be better served by a MySQL Enterprise subscription. Choosing Between Binary and Source Distributions Sun Microsystems makes both source and binary distributions of the MySQL database server available for download on their website. As of this writing, binary distributions are available for Linux (Red Hat, SuSE, and generic distributions), Solaris, FreeBSD, Mac OS X, 32-bit and 64-bit Windows, HP-UX, and IBM AIX and IBM i5, and source distributions are available for both Windows and UNIX platforms. Windows users must further choose between three different binary distributions: the “Essentials” distribution, which includes the minimum set of files and an automated installer; the “Complete” distribution, which includes everything in the “Essentials” distribution plus additional tools such as the MySQL Benchmark Suite; and the “Noinstall” distribution, which includes everything in the “Complete” distribution except the automated installer. In most cases, it’s preferable to use a precompiled binary distribution rather than a source distribution, for two reasons: It is easier to install, and it has been optimized for maximum performance on different platforms by the MySQL development team. That said, there are a number of possible situations where a source distribution might be preferable to a binary distribution. You need to recompile MySQL with different compile-time options from the • defaults provided by the MySQL team (for example, to set a different value for the default installation path). You need to compile a smaller, lighter version of MySQL that doesn’t include all • the features (and overhead) of the standard binary distribution. You need newer, experimental features that are disabled by default in the • standard binaries. You need to make modifications to the server’s source code.• Source distributions are typically used only by experienced developers who either need to tweak MySQL’s default values for their own purposes or who are interested in studying the source code to see how it works. Such users usually also have the time, inclination, and expertise to diagnose and troubleshoot compilation and configuration issues that may arise during the installation process. MySQL versions that don’t come with an automated installer are usually packaged in either TGZ or ZIP format. Therefore, users on both UNIX and Windows platforms will need a decompression tool capable of dealing with Tape Archive (TAR) and GNU Zip (GZ) files. On UNIX, the tar and gzip utilities are appropriate, and are usually included with the operating system. On Windows, a good decompression tool is WinZip, available from www.winzip.com. 322 Part II: Administration The instructions in the following sections assume that you will be using a binary distribution of MySQL Community Server. This distribution can be downloaded from the MySQL website. The MySQL software is also mirrored on a number of other sites around the world, and you can make your download more efficient by selecting the site that is geographically closest to you. Once downloaded, move to the section titled “Installing and Configuring MySQL.” Installing and Configuring MySQL The next step is to install and configure MySQL for your specific platform. The following sections outline the steps for both Windows and UNIX platforms. Installing on UNIX MySQL is available in binary form for almost all versions of UNIX, and can be compiled from source for those UNIX variants for which no binary distribution exists. This section will discuss installing and configuring MySQL on Linux using a binary distribution; the process for other UNIX variants is similar, though you should refer to the documentation included with the MySQL distribution for platform-specific notes. To install MySQL from a binary distribution, use the following steps: 1. Ensure that you are logged in as the system’s “root” user. [user@host]# su – root 2. Extract the contents of the MySQL binary archive to an appropriate directory on your system—for example, /usr/local/: [root@host]# cd /usr/local [root@host]# tar -xzvf /tmp/mysql-5.1.30-linux-i686-glibc23.tar.gz The MySQL files should get extracted into a directory named according to the format mysql-version-os-architecture—for example, mysql-5.1.30-linux-i686-glibc23. 3. For ease of use, set a shorter name for the directory created in the previous step by creating a soft link named mysql pointing to this directory in the same location: [root@host]# ln -s mysql-5.1.30-linux-i686-glibc23 mysql 4. For security reasons, the MySQL database server process should never run as the system superuser. Therefore, it is necessary to create a special “mysql” user and group for this purpose. Do this with the groupadd and useradd commands, and then change the ownership of the MySQL installation directory to this user and group: [root@host]# groupadd mysql [root@host]# useradd –g mysql mysql [root@host]# chown -R mysql /usr/local/mysql [root@host]# chgrp -R mysql /usr/local/mysql [...]... 233–236 MySQL Cluster, 8 mysql command, 25 MySQL Community Server, 320–322 MySQL Database Server, 9 MySQL Embedded Sever, 9 MySQL Enterprise Server, 320 MySQL Migration Toolkit, 9 mysql prompt, 26 MySQL Proxy, 8 MySQL Query Browser, 9 MySQL Server, 8 command-line options, 251 passwords, 250 MySQL Server Instance Config Wizard, 326 MySQL Workbench, 9 mysqladmin extended-status command, 215, 247 mysqladmin... 246 mysqladmin status command, 247 mysqladmin utility, 244–245, 246 mysqladmin variables command, 253 mysqladmin version command, 247 mysqlbinlog utility, 290 mysqld.exe server binary, 331 mysqld_safe wrapper, 245–246, 250 mysqldump utility, 195, 210, 295–298, 306–307 backup files and, 310 data backup and, 243 mysqlimport utility, 243 mysql_ install_db script, 323 mysql. server script, 245 341 342 MySQL. .. tables and sets up default access permissions for MySQL 6 Alter the ownership of the MySQL binaries so that they are owned by “root”: [root@host]# chown -R root /usr/local /mysql [root@host]# chown -R mysql /usr/local /mysql/ data 7 Start the MySQL server by manually running the mysqld_safe script: [root@host]# /usr/local /mysql/ bin/mysqld_safe user =mysql & MySQL should now start up normally Once installation... routines and, 148–149 user-defined, 45–46 variables command, 245 version command, 245 VERSION () function, 247 version mismatch, 302 views, 95 107 constraints, 106 107 joins and, 105 106 multitable, 100 102 nested, 102 security, 100 simple, 96 100 updatable, 103 105 VIEWS table, 257 W Web applications, 14–15 WEEK unit, 185 WHEN-THEN blocks, 153 WHERE clause, 29, 34 comparison operator and, 40 exporting... prompt# mysql -u root You should be rewarded with a prompt, as shown: At this point, you are connected to the MySQL server and can begin executing SQL commands or queries to test whether the server is working as it should Here are a few examples, with their output: mysql> SHOW DATABASES; + + | Database | + + | mysql | | test | + + 2 rows in set (0.13 sec) mysql> USE mysql; Database changed mysql> ... 273–275 triggers and, 168 updateable views and, 103 104 views and, 96 UpdateXML () function, 202–203 uptime, 242–243 USAGE privilege, 279 user accounts, 282–285 MySQL v system, 269 user table, 265–268, 276–277, 295 useradd command, 322 user-defined function (UDF), 304 USER_PRIVILEGES table, 257–258 USING clause, 78 self-joins and, 80 347 348 MySQL Database Usage & Administration V VALUES clause, 33 VARCHAR... Sample Database 327 PART II Figure A-6  Selecting the configuration type Figure A-7  Setting up the MySQL service 328 Part II:  Administration Figure A-8  Setting the administrator password Figure A-9  MySQL configuration successfully completed Appendix:  Installing MySQL and the Sample Database 329 Testing MySQL First, start up the MySQL command-line client by changing to the bin/ subdirectory of your MySQL. ..Appendix:  Installing MySQL and the Sample Database 323 5 Initialize the MySQL tables with the mysql_ install_db initialization script, included in the distribution: [root@host]# /usr/local /mysql/ scripts /mysql_ install_db user =mysql Figure A-1 demonstrates what you should see when you do this As this output suggests, this initialization script prepares and installs the various MySQL base tables and... components of the package should be installed 4 MySQL should now begin installing to your system (Figure A-4) Figure A-2  Beginning MySQL installation on Windows Appendix:  Installing MySQL and the Sample Database 325 PART II Figure A-3  Selecting the MySQL installation type Figure A-4  MySQL installation in progress 326 Part II:  Administration Figure A-5  Beginning MySQL configuration on Windows 5 Once installation... Example Database The SQL commands needed to re-create the example database can be found in a single file, available from this book’s website, at www .mysql- usage. com Once you’ve downloaded this file, drop to your shell prompt, fire up the MySQL command-line client, and execute the following commands: prompt# mysql -u root -p Enter password: *** Welcome to the MySQL monitor Commands end with ; or \g Your MySQL . output: mysql& gt; SHOW DATABASES; + + | Database | + + | mysql | | test | + + 2 rows in set (0.13 sec) mysql& gt; USE mysql; Database changed mysql& gt; SHOW TABLES; + + | Tables_in _mysql. Type 'help;' or 'h' for help. Type 'c' to clear the buffer. mysql& gt; CREATE DATABASE db1; Query OK, 1 row affected (0.00 sec) mysql& gt; exit Bye prompt# mysql. groupadd mysql [root@host]# useradd –g mysql mysql [root@host]# chown -R mysql /usr/local /mysql [root@host]# chgrp -R mysql /usr/local /mysql PART II Appendix: Installing MySQL and the Sample Database