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Displaying posts with tag: tungsten (reset)
How to use Round-Robin Load Balancing with the Tungsten Connector

Overview The Skinny

Part of the power of Tungsten Clustering for MySQL / MariaDB is its intelligent MySQL Proxy, known as the Tungsten Connector. The Tungsten Connector has built-in read-write splitting capabilities, and it is also possible to configure different algorithms which select the appropriate slave (i.e. Round-Robin or Lowest-Latency).

The Question Recently, a customer asked us:

How do we best share the load between read-only slaves? Currently, there appears to be an imbalance, with most of the read-only queries reaching just one slave. What may we do to improve this situation?

This customer noticed that a couple of long …

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Enabling Autorecovery for the Tungsten Replicator

The Replicator is a critical piece of the Tungsten Clustering solution for MySQL / MariaDB, as well as its own stand-alone data replication product. Automatic recovery is a feature that enables the Replicator to go back online in the event of a transient failure. In this blog we discuss how to enable Automatic Recovery. For more information about Auto-Recovery, please click here to visit the online documentation page.

The Question Recently, a customer asked us:

We see that the replicators receive a transaction which has a deadlock error in it:

pendingError : Event application failed: seqno=82880882 fragno=0 message=java.sql.SQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction

If one performs a service online, it comes back online without issue and continues …

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In a proxy-ed world, where do connections come from?

Overview The Skinny

Database Proxies provide a single entry point into MySQL for the calling client applications.

Proxies are wonderful tools to handle various situations like a master role switch to another node for maintenance, or for transparency with read and write connections.

However, when the time comes to perform the switch action, all of the calling clients have been funneled through the proxy, so identification of the calling host from the database itself becomes difficult.

The Problem What is going on?

Let’s illustrate how not knowing the source of a client connection can be an issue for the database administrator…

In the following diagram, three client applications connect to a Tungsten Cluster via the Connector proxy:

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How to move the Relay role to another node in a Composite Tungsten Cluster

The Question Recently, a customer asked us:

How would we manually move the relay role from a failing node to a slave in a Composite Tungsten Cluster passive site?

The Answer The Long and the Short of It

There are two ways to handle this procedure manually when the usual switch command fails to work as expected. One is short and reasonably automated, and the other is much more detailed and manual.

Of course, the usual procedure is to just issue the switch command in the passive cluster:

use west
set policy maintenance
switch
set policy automatic

The below article describes what to do when the switch command does not move the relay role to another node.

SHORT

Below is the list of cctrl commands that would be run for the basic, short version, which (aside from handling policy changes) is really only …

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

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:

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Slick Command-Line Tricks for a Tungsten MySQL / MariaDB Database Cluster

Overview The Skinny

Tungsten Clustering provides high availability, disaster recovery, and a host of other benefits for MySQL / MariaDB / Percona Server databases. In this blog post we will explore some of the shell aliases I use every day to administer various Tungsten Clusters.

Shell Aliases: A Quick Review Quick and Easy

A shell alias is simply a way to create a shortcut for frequently-used command sequences.

For example, I like to shorten the command clear to cls, i.e.

shell> alias cls=clear
shell> cls

If you create an alias on the fly it will be lost when the shell exits.

To save aliases so they are available to all shell sessions, update your shell’s profile or rc script.

For example, add the below line to the bottom of …

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Where are the logs for a Tungsten Cluster?

The Question Recently, a customer asked us:

Where are the logs for a Tungsten Cluster and which are the proper log files to monitor if I do a master role switch to another node?

The Answer: Part I Both basic and advanced logs are available!

The basic logs are symbolic links into the log subdirectory for each layer of the cluster.

For example, this is the listing of the default log directory, /opt/continuent/service_logs:

connector-user.log -> /opt/continuent/tungsten/tungsten-connector/log/connector-user.log
manager-user.log -> /opt/continuent/tungsten/tungsten-manager/log/manager-user.log
mysqldump.log -> /opt/continuent/tungsten/tungsten-replicator/log/mysqldump.log
replicator-user.log -> /opt/continuent/tungsten/tungsten-replicator/log/replicator-user.log
xtrabackup.log -> /opt/continuent/tungsten/tungsten-replicator/log/xtrabackup.log

As you can see, each log file is a …

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The Fast Way to Import CSV Data Into a Tungsten Cluster

The Question Recently, a customer asked us:

After importing a new section of user data into our Tungsten cluster, we are seeing perpetually rising replication lag. We are sitting at 8.5hrs estimated convergence time after importing around 50 million rows and this lag is climbing continuously. We are currently migrating some of our users from a NoSQL database into our Tungsten cluster. We have a procedure to write out a bunch of CSV files after translating our old data into columns and then we recursively send them to the write master using the mysql client. Specifically our import SQL is doing LOAD DATA LOCAL INFILE and the reading in a large CSV file to do the import. We have 20k records per CSV file and we have 12 workers which insert them in parallel.

Simple Overview The Skinny

In cases like this, the slaves are having trouble with the database unable to keep up with the apply stage …

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What is the Best Way to Check the Health of a Tungsten Cluster Before a Switch?

The Question Recently, a customer asked us:

What would cause a node switch to fail in a Tungsten Cluster?

For example, we saw the following during a recent session where a switch failed:

cctrl> switch to db3 

SELECTED SLAVE: db3@alpha 
SET POLICY: MAINTENANCE => MAINTENANCE 
PURGE REMAINING ACTIVE SESSIONS ON CURRENT MASTER 'db1@alpha' 
PURGED A TOTAL OF 0 ACTIVE SESSIONS ON MASTER 'db1@alpha' 
FLUSH TRANSACTIONS ON CURRENT MASTER 'db1@alpha' 
Exception encountered during SWITCH. 
Failed while setting the replicator 'db1' role to 'slave' 
ClusterManagerException: Exception while executing command 'replicatorStatus' on manager 'db1' 
Exception=Failed to execute '/alpha/db1/manager/ClusterManagementHelper/replicatorStatus alpha db3' 
Reason= 
CLUSTER_MEMBER(true) 
STATUS(FAIL) 
+----------------------------------------------------------------------------+ 
|alpha | …
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What on Earth is a Split-Brain Scenario in a MySQL Database Cluster?

Overview The Skinny

In this blog post we will define what a split-brain scenario means in a MySQL database cluster, and then explore how a Tungsten MySQL database cluster reacts to a split-brain situation.

Agenda What’s Here?

  • Define the term “split-brain”
  • Briefly explore how the Tungsten Manager works to monitor the cluster health and prevent data corruption in the event of a network partition
  • Also explore how the Tungsten Connector works to route writes
  • Describe how a Tungsten MySQL database cluster reacts to a split-brain situation
  • Illustrate various testing and recovery procedures

Split-Brain: Definition and Impact Sounds scary, and it is!

A split-brain occurs when a MySQL database cluster which normally has …

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