Overview The Skinny

When it comes to zero downtime, proxies are the first line components of a cluster.

In order to achieve High Availability (HA) for MySQL, MariaDB and Percona Server, a commonly deployed setup consists of configuring load balancers (hardware or software) on top of those proxies.

A Strong Architecture How is Maintenance Made Possible?

With this proxy + load balancer architecture, server maintenance is made possible on any of the proxy hosts, as follows:

• the proxy is stopped
• the load balancer detects the dead proxy and removes it from the pool
• new connection requests go to live proxies

The Problem What Happens to Existing Sessions?

But wait… even though new connections are re-routed correctly, what happens …

Background The Skinny

Performing schema changes often requires extended downtime for applications. This is due to MySQL needing to rebuild tables for common schema change operations. Tools like pt-online-schema-change have been written to try to overcome the downtime associated with schema changes, however they are complex and put a high load on the database. Amazon’s Aurora improves some schema changes operations, but still requires a table rebuild for common operations like adding a column using before or after, or simply to add a column with a default value. Rebuilding a table with millions of rows can take hours and prevent writes to that table the entire time.

How Can Tungsten Clustering Keep Applications Running? How Does It All Work?

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Overview The Skinny

In this blog post we will discuss how the managed cross-site replication streams work in a Composite Multi-Master Tungsten Cluster for MySQL, MariaDB and Percona Server.

Agenda What’s Here?

• Briefly explore how managed cross-site replication works in a Tungsten Composite Multi-Master Cluster
• Describe the reasons why the default design was chosen
• Explain the pros and cons of changing the configuration
• Examine how to change the configuration of the managed cross-site replicators

Cross-Site Replication A Very Brief Summary

In a standard Composite Multi-Master (CMM) deployment, the managed cross-site replicators pull Transaction History Logs (THL) from every remote cluster’s current master node. …

The Question Recently, a customer asked us:

If we move to using the INI configuration method instead of staging, would password-less SSH still be required?

The Answer The answer is both “Yes” and “No”

No, for installation and updates/upgrades specifically. Since INI-based configurations force the tpm command to act upon the local host only for installs and updates/upgrades, password-less SSH is not required.

Yes, because there are certain commands that do rely upon password-less SSH to function. These are:

• tungsten_provision_slave
• prov-sl.sh
• multi_trepctl
• tpm diag (pre-6.0.5)
• tpm diag --hosts (>= 6.0.5)
• Any tpm-based backup and restore operations that involve a remote node

Summary The Wrap-Up

In …

Overview The Skinny

In this blog post we will discuss how to best integrate various Continuent-bundled cluster monitoring solutions with PagerDuty (pagerduty.com), a popular alerting service.

Agenda What’s Here?

• Briefly explore the bundled cluster monitoring tools
• Describe the procedure for establishing alerting via PagerDuty
• Examine some of the multiple monitoring tools included with the Continuent Tungsten Clustering software, and provide examples of how to send an email to PagerDuty from each of the tools.

Exploring the Bundled Cluster Monitoring Tools A Brief Summary

Continuent provides multiple methods out of the box to monitor the cluster health. The most popular is the suite of Nagios/NRPE scripts (i.e. cluster-home/bin/check_tungsten_*). We also have Zabbix scripts (i.e. cluster-home/bin/zabbix_tungsten_*). Additionally, there is …

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 …