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The slow query log is the trusted old method of recording slow query, so the database administrator can determine which queries are in the most need for optimization. Since MySQL 5.6, it has to some extend been overshadowed by the Performance Schema which has lower overhead and thus allows collecting statistics about all queries. The slow query log has one major advantage though: the data is persisted. In MySQL 8.0.14 which was recently released, there is an improvement for the slow query log: additional statistics about the recorded queries.

The slow query log with log_slow_extra enabled.

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In a MySQL hosting replication setup, the parameter Seconds_Behind_Master (SBM), as displayed by the SHOW SLAVE STATUS command, is commonly used as an indication of the current replication lag of the slave. In this blog post, we examine how to understand and interpret this value in various situations.

Possible Values of  Seconds Behind Master

The value of SBM, as explained in the  MySQL documentation, depends on the state of the MySQL slave in general, and the states of MySQL slave SQL_THREAD and IO_THREAD in particular. While IO_THREAD connects with the master and reads the updates, SQL_THREAD applies these updates on the slave. Let’s examine the possible values of SBM during different states of the MySQL Slave.

When SBM Value is Null

• SBM is …

I am a Junior DBA at Mydbops. This is my first blog professionally, I would like to brief my encounter with Log-rotate in first few weeks of my work,  Hope it will help other beginners as well. This Blog will cover the following sections.

• Introduction to Log-rotate

• Issues Faced

• Solutions (Fix for the above issues)

• Best practices

  • How to configure the Log-rotate

  • Operation of Log-rotate

  • Files responsible for the Log_rotate utility.

1.0. Introduction to Log-rotate:

• Log-rotate is a utility and …

Have you been experiencing slow MySQL startup times in GTID mode? We recently ran into this issue on one of our MySQL hosting deployments and set out to solve the problem. In this blog, we break down the issue that could be slowing down your MySQL restart times, how to debug for your deployment, and what you can do to decrease your start time and improve your understanding of GTID-based replication.

How We Found The Problem

We were investigating slow MySQL startup times on a low-end, disk-based MySQL 5.7.21 deployment which had GTID mode enabled. The system was part of a master-slave pair and was under a moderate write load. When restarting during a scheduled maintenance, we …

MySQL 8.0.13 improves replication lag monitoring by extending the instrumentation for transaction transient errors. These temporary errors, which include lock timeouts caused by client transactions executing concurrently as the slave is replicating, do not stop the applier thread: instead, they cause a transaction to retry.…

One important way to protect your data is to keep your Tungsten Clustering software up-to-date.

A standard cluster deployment uses three nodes, which allows for no-downtime upgrades along with the ability to have a fully available cluster during maintenance.

Please note that with only two database cluster nodes, there is a window of vulnerability created by leaving zero failover candidates available when the lone slave is taken down for service.

The Best Practices: Staging Performing a No-Downtime Upgrade for a Staging Deployment

When upgrading a Staging-style deployment, all nodes are upgraded at once in parallel via the tools/tpm update command run from inside the staging directory on the staging host.

No Master switch happens, and all layers are restarted to use the new code. …

Tungsten Clustering is an extraordinarily flexible tool, with options at every layer of operation.

In this blog post, we will describe and discuss the two different methods for installing, updating and upgrading Tungsten Clustering software.

When first designing a deployment, the question of installation methodology is answered by inspecting the environment and reviewing the customer’s specific needs.

Staging Deployment Methodology

All for One and One for All

Staging deployments were the original method of installing Tungsten Clustering, and relied upon command-line tools to configure and install all cluster nodes at once from a central location called the staging server.

This staging server (which could be one of the cluster nodes) requires SSH access to all …

Your database cluster contains your most business-critical data and therefore proper performance under load is critical to business health. If response time is slow, customers (and staff) get frustrated and the business suffers a slow-down.

If the database layer is unable to keep up with demand, all applications can and will suffer slow performance as a result.

To prevent this situation, use load tests to determine the throughput as objectively as possible.

In the sample load.pl script below, increase load by increasing the thread quantity.

You could also run this on a database with data in it without polluting the existing data since new test databases are created to match each node’s hostname for uniqueness.

Note: The examples in this blog post assume that a Connector is …

In a previous post we went into detail about how to implement Tungsten-specific checks. In this post we will focus on the other standard Nagios checks that would help keep your cluster nodes healthy.

Your database cluster contains your most business-critical data. The slave nodes must be online, healthy and in sync with the master in order to be viable failover candidates.

This means keeping a close watch on the health of the databases nodes from many perspectives, from ensuring sufficient disk space to testing that replication traffic is flowing.

A robust monitoring setup is essential for cluster health and viability – if your replicator goes offline and you do not know about it, then that slave becomes effectively useless because it has stale data.

Nagios Checks The Power of Persistence

One …

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Since MySQL 5.6, the digest feature of the MySQL Performance Schema has provided a convenient and effective way to obtain statistics of queries based on their normalized form. The feature works so well that it has almost completely (from my experience) replaced the connector extensions and proxy for collecting query statistics for the Query Analyzer (Quan) in MySQL Enterprise Monitor (MEM).

MySQL 8 adds further improvements to the digest feature in the Performance Schema including a sample query with statistics for each digest, percentile information, and a histogram summary. This blog will explore these new features.

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