8 common (but deadly) MySQL operations mistakes and how to avoid them

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This release contains 1 new feature and 15 pt-table-checksum binlog_format mixed fixes. This release contains 3 new features and 2 bug fixes. Added --max-flow-ctl option with a value set in percent. When a Percona XtraDB Cluster node is very loaded, it sends flow control signals to the other nodes to stop sending transactions in order to catch up. When the average value of time spent in this state in percent exceeds the maximum provided in the option, the tool pt-table-checksum binlog_format mixed until it falls below again.

Added the --sleep option for pt-online-schema-change to avoid performance problems. The option accepts float values in seconds. This feature was requested in the following bug: Implemented ability to specify --check-slave-lag multiple times. The following example enables lag checks for two slaves:.

Before, the tool would die if any slave connection was lost. Now pt-table-checksum binlog_format mixed tool waits forever for slaves. The tool now checks replication lag every rows instead of every row, which significantly improves efficiency.

Adding underscores to constraints when using pt-online-schema-change can create issues with constraint name length. Before, multiple schema changes lead to underscores stacking up on the name of the constraint until it reached the 64 character limit.

Now there is a limit of two underscores in the prefix, then the tool alternately removes or adds one underscore, attempting to make the name unique. When comparing table size with the slave table, the tool now ignores --chunk-size-limit if it is set to zero to avoid multiplying by zero. Fixed the documentation for --check-interval to reflect its correct behavior.

ReadKeyMini causes pt-online-schema-change session to lock under some circumstances. Removed ReadKeyMini, because it is no longer necessary. The tool now issues an error when --purge and --no-delete are pt-table-checksum binlog_format mixed together. This release contains two new features and seventeen bug fixes. This release contains one new feature and twelve pt-table-checksum binlog_format mixed fixes.

This release contains one new feature and seven bug fixes. This release contains seven bug fixes. This release contains six bug fixes. This release contains five bug fixes. This release has pt-table-checksum binlog_format mixed new features and six bug fixes.

Percona Toolkit packages can be downloaded from http: This release has only one bug fix. This fix removed that ability. This release has 16 bug fixes and a few new features. One bug fix is very important, so 2. Until recently, either no one had this problem, or no one reported it, or no one realized that pt-table-sync caused it. In the pt-table-checksum binlog_format mixed case, pt-table-sync could delete all rows in child tables, which is quite surprising and bad.

The tool is better now. This was poor feedback from the tool more than a bug. There was a point in the tool where it waited forever for slaves to catch up, but pt-table-checksum binlog_format mixed did this silently.

The change is that pt-mysql-summary no longer prompts to dump and summarize schemas. To do this, you must specify —databases or, a new option, —all-databases. Several users said this behavior was better, so we made the change even though some might consider it a backwards-incompatible change.

This release has four new features and a number of bugfixes. As of pt-table-checksum 2. An exit status of zero or 32 is equivalent to a zero exit status with skipped chunks in previous versions of the tool.

New —no-drop-triggers option pt-table-checksum binlog_format mixed been implemented for pt-online-schema-change in case users want to rename the tables manually, when the load is low. New —new-table-name option has been added to pt-online-schema-change which can be used to specify the temporary table name. This release two new features and a number of bugfixes. Some people might not want this because it exposes real data. New option, —output json-anon, has been implemented.

This option will provide the same data without query examples. When using drop swap with pt-online-schema-change there is some production impact. This impact pt-table-checksum binlog_format mixed be measured because tool outputs the current timestamp pt-table-checksum binlog_format mixed lines for operations that may take awhile.

The pt-online-schema-change bug pt-table-checksum binlog_format mixed is bug This is the second release of the 2. Users may note the revival of the —show-all option in pt-query-digest.

This had been removed in 2. A new —recursion-method was added to pt-table-checksum: This pt-table-checksum binlog_format mixed a case where the tool could corrupt data by double-encoding.

This is now fixedbut remains relatively dangerous if using DBD:: This is another solid bug fix release, and all users are encouraged to upgrade.

This is the first release in the new 2. We plan to do one more bug fix release for 2. Here are the highlights:. We started beta support for MySQL 5. Check out the Percona Toolkit supported platforms and versions: Now —set-vars is used to set both of these or any system pt-table-checksum binlog_format mixed.

What does this all mean? Now that we have four base versions of MySQL 5. Moreover, it has pt-table-checksum binlog_format mixed really helpful new feature: Basically, we re-focused it on its primary objective: So the ability to parse memcached, Postgres, Apache, and other logs was removed.

The result is a simpler, more focused tool, i. This feature is still in development while we determine the pt-table-checksum binlog_format mixed JSON structure. Way back in 2. For example, there are two versions of the DBD:: And pt-table-checksum binlog_format mixed are certain versions of MySQL that have critical bugs.

Version check will warn you about these if your system is running them. SSL Perl module is installed easily available through your package managerit will use a secure https connection over the web, else it pt-table-checksum binlog_format mixed use a standard http connection. We removed pt-query-advisor, pt-tcp-model, pt-trend, and pt-log-player.

Granted, no tool is ever really gone: The other tools were special projects that were not widely used. So now the command line is what you expect: Originally, pt-stalk —no-stalk was meant to simulate pt-collect, pt-table-checksum binlog_format mixed. To do that, the tool magically set some options and clobbered others, resulting in no way to do repeated collections at intervals.

Now —no-stalk means only that: So to collect once pt-table-checksum binlog_format mixed exit: Similar to the pt-stalk —no-stalk changes, pt-fk-error-logger and pt-deadlock-logger received mini overhauls in 2. And each treated their run-related options a little differently.

This magic is gone now: There were other miscellaneous bug fixes pt-table-checksum binlog_format mixed, too. As the first release in a new series, 2. In other words, we may pt-table-checksum binlog_format mixed things like the pt-query-digest —output json format in future releases after receiving real-world feedback.

Users are encouraged to begin upgrading, particularly given that, except for the forthcoming 2. If you upgrade from 2. This release primarily aims to restore backwards-compatibility with pt-heartbeat 2. Unfortunately, these changes caused a pt-table-checksum binlog_format mixed of precision and, if mixing versions of pt-heartbeat, made the tool report a huge amount of replication lag.

This release makes the tool compatible with pt-heartbeat 2. This is an important bug fix for pt-table-sync: However, standard MySQL does not warn in this case, despite the docs saying that it should.

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Replication is asynchronous by default; slaves do not need to be connected permanently to receive updates from the master. Depending on the configuration, you can replicate all databases, selected databases, or even selected tables within a database.

Scale-out solutions - spreading the load among multiple slaves to improve performance. In this environment, all writes and updates must take place on the master server. Reads, however, may take place on one or more slaves. This model can improve the performance of writes since the master is dedicated to updates , while dramatically increasing read speed across an increasing number of slaves. Data security - because data is replicated to the slave, and the slave can pause the replication process, it is possible to run backup services on the slave without corrupting the corresponding master data.

Analytics - live data can be created on the master, while the analysis of the information can take place on the slave without affecting the performance of the master. Long-distance data distribution - you can use replication to create a local copy of data for a remote site to use, without permanent access to the master.

The traditional method is based on replicating events from the master's binary log, and requires the log files and positions in them to be synchronized between master and slave. The newer method based on global transaction identifiers GTIDs is transactional and therefore does not require working with log files or positions within these files, which greatly simplifies many common replication tasks.

Replication using GTIDs guarantees consistency between master and slave as long as all transactions committed on the master have also been applied on the slave. Replication in MySQL supports different types of synchronization. The original type of synchronization is one-way, asynchronous replication, in which one server acts as the master, while one or more other servers act as slaves.

There are a number of solutions available for setting up replication between servers, and the best method to use depends on the presence of data and the engine types you are using. Replication is controlled through a number of different options and variables.

You can use replication to solve a number of different problems, including performance, supporting the backup of different databases, and as part of a larger solution to alleviate system failures. This section describes how to configure the different types of replication available in MySQL and includes the setup and configuration required for a replication environment, including step-by-step instructions for creating a new replication environment.

The major components of this section are:. Events in the binary log are recorded using a number of formats. Once started, the replication process should require little administration or monitoring. The information in the binary log is stored in different logging formats according to the database changes being recorded. Slaves are configured to read the binary log from the master and to execute the events in the binary log on the slave's local database. Each slave receives a copy of the entire contents of the binary log.

It is the responsibility of the slave to decide which statements in the binary log should be executed. Unless you specify otherwise, all events in the master binary log are executed on the slave.

If required, you can configure the slave to process only events that apply to particular databases or tables. Each slave keeps a record of the binary log coordinates: This means that multiple slaves can be connected to the master and executing different parts of the same binary log. Because the slaves control this process, individual slaves can be connected and disconnected from the server without affecting the master's operation. Also, because each slave records the current position within the binary log, it is possible for slaves to be disconnected, reconnect and then resume processing.

The master and each slave must be configured with a unique ID using the server-id option. In addition, each slave must be configured with information about the master host name, log file name, and position within that file. This section describes how to set up a MySQL server to use binary log file position based replication.

There are a number of different methods for setting up replication, and the exact method to use depends on how you are setting up replication, and whether you already have data within your master database.

On the master, you must enable binary logging and configure a unique server ID. This might require a server restart. On each slave that you want to connect to the master, you must configure a unique server ID. Optionally, create a separate user for your slaves to use during authentication with the master when reading the binary log for replication.

Before creating a data snapshot or starting the replication process, on the master you should record the current position in the binary log. You need this information when configuring the slave so that the slave knows where within the binary log to start executing events. If you already have data on the master and want to use it to synchronize the slave, you need to create a data snapshot to copy the data to the slave.

The storage engine you are using has an impact on how you create the snapshot. When you are using MyISAM , you must stop processing statements on the master to obtain a read-lock, then obtain its current binary log coordinates and dump its data, before permitting the master to continue executing statements. If you do not stop the execution of statements, the data dump and the master status information will not match, resulting in inconsistent or corrupted databases on the slaves.

If you are using InnoDB , you do not need a read-lock and a transaction that is long enough to transfer the data snapshot is sufficient. Configure the slave with settings for connecting to the master, such as the host name, login credentials, and binary log file name and position.

If you do not have this privilege, it might not be possible to enable replication. To configure a master to use binary log file position based replication, you must enable binary logging and establish a unique server ID.

If this has not already been done, a server restart is required. Binary logging must be enabled on the master because the binary log is the basis for replicating changes from the master to its slaves. If binary logging is not enabled on the master using the log-bin option, replication is not possible. Each server within a replication group must be configured with a unique server ID. How you organize and select the numbers is your choice. Within the [mysqld] section of the configuration file, add the log-bin and server-id options.

If these options already exist, but are commented out, uncomment the options and alter them according to your needs. For example, to enable binary logging using a log file name prefix of mysql-bin , and configure a server ID of 1, use these lines:. Ensure that the skip-networking option is not enabled on your replication master. If networking has been disabled, the slave cannot communicate with the master and replication fails.

Each slave connects to the master using a MySQL user name and password, so there must be a user account on the master that the slave can use to connect. You can choose to create a different account for each slave, or connect to the master using the same account for each slave.

Therefore, you may want to create a separate account that has privileges only for the replication process, to minimize the possibility of compromise to other accounts. For example, to set up a new user, repl , that can connect for replication from any host within the mydomain. To configure the slave to start the replication process at the correct point, you need the master's current coordinates within its binary log.

In that case, the values that you need to use later when specifying the slave's log file and position are the empty string '' and 4. If the master has been binary logging previously, use this procedure to obtain the master binary log coordinates:.

If you exit the client, the lock is released. The File column shows the name of the log file and the Position column shows the position within the file. In this example, the binary log file is mysql-bin. You need them later when you are setting up the slave.

They represent the replication coordinates at which the slave should begin processing new updates from the master. You now have the information you need to enable the slave to start reading from the binary log in the correct place to start replication.

The next step depends on whether you have existing data on the master. Choose one of the following options:. If you have existing data that needs be to synchronized with the slave before you start replication, leave the client running so that the lock remains in place. This prevents any further changes being made, so that the data copied to the slave is in synchrony with the master.

If you are setting up a new master and slave replication group, you can exit the first session to release the read lock.

If the master database contains existing data it is necessary to copy this data to each slave. There are different ways to dump the data from the master database. The following sections describe possible options. To select the appropriate method of dumping the database, choose between these options:.

Use the mysqldump tool to create a dump of all the databases you want to replicate. This is the recommended method, especially when using InnoDB.

If your database is stored in binary portable files, you can copy the raw data files to a slave. This can be more efficient than using mysqldump and importing the file on each slave, because it skips the overhead of updating indexes as the INSERT statements are replayed. With storage engines such as InnoDB this is not recommended. To create a snapshot of the data in an existing master database, use the mysqldump tool. Once the data dump has been completed, import this data into the slave before starting the replication process.

The following example dumps all databases to a file named dbdump. If you do not use --master-data , then it is necessary to lock all tables in a separate session manually. It is possible to exclude certain databases from the dump using the mysqldump tool. If you want to choose which databases to include in the dump, do not use --all-databases. Choose one of these options:. Exclude all the tables in the database using --ignore-table option. Name only those databases which you want dumped using the --databases option.

To import the data, either copy the dump file to the slave, or access the file from the master when connecting remotely to the slave. This section describes how to create a data snapshot using the raw files which make up the database. How the storage engine responds to this depends on its crash recovery abilities.

This command records the log name and offset corresponding to the snapshot to be used on the slave.