Overview The Skinny

Part of the power of Tungsten Clustering for MySQL / MariaDB is its intelligent MySQL Proxy, known as the Tungsten Connector. Tungsten Connector has three main modes, and depending on the type of operations you are performing (such as if you need read-write splitting), we help you choose which mode is best.

The Question Recently, a customer asked us:

How can I tell which Tungsten Connector mode I am using: Bridge, Proxy/Direct or Proxy/SmartScale?

The Answer Connect and Observe

You may login through the Connector to tell the difference between Bridge mode and Proxy mode (either Direct or SmartScale):

In Proxy mode, you will see the -tungsten tag appended to the Server version string:

 …

Overview The Skinny

In this blog post we will discuss how to use the Tungsten Connector keep-alive feature to ensure long-running MySQL & MariaDB/Percona Server client sessions stay connected in a Tungsten Cluster.

Agenda What’s Here?

• Briefly explore how the Tungsten Connector works
• Describe the Connector keep-alives – what are they and why do we use them?
• Discuss why the keep-alive feature is not available in Bridge mode and why
• Examine how to tune the keep-alive feature in the Tungsten Connector

Tungsten Connector: A Primer A Very Brief Summary

The Tungsten Connector is an intelligent MySQL database proxy located between the clients and the database servers, providing a single connection point, while routing queries to …

In this blog post, we demonstrate how to convert a single standalone cluster into a Composite Primary/DR topology running in two data centers.

Our example starting cluster has 5 nodes (1 master and 4 slaves) and uses service name alpha. Our target cluster will have 6 nodes (3 per cluster) in 2 member clusters alpha_east and alpha_west in composite service alpha.

This means that we will reuse the existing service name alpha as the name of the new composite service, and create two new service names, one for each cluster (alpha_east and alpha_west).

Below is an INI file extract example for our starting standalone cluster with 5 nodes:

[defaults]
...

[alpha]
connectors=db1,db2,db3,db4,db5
master=db1
members=db1,db2,db3,db4,db5
topology=clustered

To convert the above configuration to a Composite Primary/DR:

1. First you must stop all services on all existing nodes:

   shell> stopall
   

   …

In this blog post, we talk about what happened during an installation of the Tungsten Cluster into an environment with SELinux running and mis-configured.

An attempt to execute `tpm install` on v5.3.2 recently failed with the below error:

ERROR >> node3_production_customer_com >> Unable to run 'sudo systemctl status mysqld.service' or the database server is not running (DatasourceBootScriptCheck) 
Update the /etc/sudoers file or disable sudo by adding --enable-sudo-access=false 

Worse, this customer reported that this appeared as a WARNING only in Dev and Staging tests. So we checked, and it seemed we were able to access systemctl properly:

shell> sudo systemctl status mysqld.service
● mysqld.service - MySQL Percona Server
Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
Active: activating (start-post) since Tue 2018-06-19 17:46:19 BST; 1min 15s ago …

In this blog post, we talk about how to configure automatic start at boot time for the Tungsten Clustering components.

By default, Tungsten Clustering does not start automatically on boot. To enable Tungsten Clustering to start at boot time, use the deployall script provided to create the necessary boot scripts:

shell> sudo /opt/continuent/tungsten/cluster-home/bin/deployall

To disable automatic startup at boot time, use the undeployall command:

shell> sudo /opt/continuent/tungsten/cluster-home/bin/undeployall

For Multisite/Multimaster deployments in specific, there are separate cross-site replicators running. In this case, a custom startup script must be created, otherwise the replicator will be unable to start as it has been configured in a different directory.

1. Create a link from the Tungsten Replicator service startup script in the operating system …

In this blog post, we talk about the Automatic Reconnect feature in the Tungsten Connector.

Automatic reconnect enables the Connector to re-establish a connection in the event of a transient failure. Under specific circumstances, the Connector will also retry the query.

Connector automatic reconnect is enabled by default in Proxy and Smartscale modes.

Use the following tpm command option on the command line (remove the leading hyphens inside INI files):

--connector-autoreconnect=false

to disable automatic reconnect.

This feature is not available while running in Bridge Mode. Use the tpm command option --connector-bridge-mode=false to disable Bridge mode.

Automatic reconnect enables retries of statements under the following circumstances:

• not in bridge mode
• not inside a transaction
• no temp table has been created
…

In this blog post, we talk about how existing client connections are handled by the Tungsten Connector when a manual master role switch is invoked and how to adjust that behavior.

When a graceful switch is invoked via cctrl or the Tungsten Dashboard, by default the Connector will wait for five (5) seconds to allow in-flight activities to complete before forcibly disconnecting all active connections from the application side, no matter what type of query was in use.

If connections still exist after the timeout interval, they are forcibly closed, and the application will get back an error.

This configuration setting ONLY applies to a manual switch. During a failover caused by loss of MySQL availability, there is no wait and all connections are force-closed immediately.

This timeout is adjusted via the tpm option …

In this blog post, we talk about how query connections are handled by the Tungsten Connector, especially read-only connections.

There are multiple ways to configure session handling in the Connector. The three main modes are Bridge, Proxy/Direct and Proxy/SmartScale.

In Bridge mode, the data source to connect to is chosen ONCE for the lifetime of the connection, which means that the selection of a different node will only happen if a NEW connection is opened through the Connector.

So if your application reuses its connections, all traffic sent through that session will continue to land on the selected read slave, i.e., when using connection pooling.

http://docs.continuent.com/tungsten-clustering-6.0/connector-bridgemode.html

The key difference is in how the slave latency checking is handled: …