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Displaying posts with tag: failover (reset)
Installing MEM agent in a cluster on the physical hosts

To install the MEM agent in a way that both physical servers are listed in the MEM dashboard, you have to install the agent on both physical nodes. But: Do not start the agent after the installation!There are three different IDs in MEM: agent-uuid, mysql-uuid and host-id. Usually they are generated automatically and you will never notice these IDs. For more information about the meaning of the different IDs look at this very good explanation from Jonathon Coombes.The agent stores the uuid and the hostid in a MySQL table called mysql.inventory. After a failover the other agent on the new node will notice "wrong" hostid and uuid entries in the inventory table. The agent will stop and ask you to TRUNCATE mysql.inventory. But with this procedure MEM creates a new instance, so all old data is lost. Not good for a failover environment.So in case of a …

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MySQL University session Oct 22: Dual Master Setups With MMM

This Thursday (October 22nd, 13:00 UTC), Walter Heck (of Open Query) will present Dual Master Setups With MMM. MMM (Multi-Master Replication Manager for MySQL) is a set of flexible scripts to perform monitoring/failover and management of MySQL master-master replication configurations (with only one node writable at any time). Session slides (PDF).

The toolset also has the ability to read balance standard master/slave configurations with any number of slaves, so you can use it to move virtual IP addresses around a group of servers depending on whether they are behind in replication. For more
information, see mysql-mmm.org.

For MySQL University sessions you point your browser …

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Dogfood: making our systems more resilient

This is a “dogfood” type story (see below for explanation of the term)… Open Query has ideas on resilient architecture which it teaches (training) and recommends (consulting, support) to clients and the general public (blog, conferences, user group talks). Like many other businesses, when we first started we set up our infrastructure quickly and on the cheap, and it’s grown since. That’s how things grow naturally, and is as always a trade-off between keeping your business running and developing while also improving infrastructure (business processes and technical).

Quite a few months ago we also started investing (mostly time) in the technical infrastructure, and slowly moving the various systems across to new servers and splitting things up along the way. Around the same time, the main webserver frequently became unresponsive. I’ll spare you the details, we know what the problem was and it was predictable, but since it wasn’t …

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Failure scenarios and solutions in master-master replication

I’ve been thinking recently about the failure scenarios of MySQL replication clusters, such as master-master pairs or master-master-with-slaves. There are a few tools that are designed to help manage failover and load balancing in such clusters, by moving virtual IP addresses around. The ones I’m familiar with don’t always do the right thing when an irregularity is detected. I’ve been debating what the best way to do replication clustering with automatic failover really is.

I’d like to hear your thoughts on the following question: what types of scenarios require what kind of response from such a tool?

I can think of a number of failures. Let me give just a few simple examples in a master-master pair:

Problem: Query overload on the writable master makes mysqld unresponsive
Do nothing. Moving the queries to another server will cause cascading failures.
Problem: The …
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More information about running MySQL on Open HA Cluster / Solaris Cluster


A while ago we published an interview with Detlef Ulherr and Thorsten Früauf about Solaris Cluster / OpenHA Cluster on the MySQL Developer Zone.

We received a number of followup questions from our readers, requesting more technical background information. For example, Mark Callaghan was wondering about the following:

  • How is failure detection done?
  • How is promotion of a slave to the master done after failure detection?
  • How are other slaves failed to the new master?

I asked Detlef to elaborate some more on the technical details of this solution. Here's his very exhaustive reply, thank you very much, Detlef!

I would also like to point out that he'll be …

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How to use JDBC (Connector/J) with MySQL Cluster

Last week I helped a customer setup a JBoss application against MySQL Cluster. It turns out it is not immediately obvious how you should setup our JDBC connector to do loadbalancing and failover. For instance, setting the connector up for an Master-Slave setup (with MySQL Enterprise) is well documented, but not doing the same with MySQL Cluster.

It's not really properly documented in the manual part, but I found in the changelogs, and confirmed on IRC that to do load-balancing across the SQL nodes in MySQL Cluster, you would use a different JDBC connection string with the "loadbalance" keyword added...


jdbc:mysql:loadbalance://host-1,host-2,...host-n/database

That does indeed …

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How to use JDBC (Connector/J) with MySQL Cluster

Last week I helped a customer setup a JBoss application against MySQL Cluster. It turns out it is not immediately obvious how you should setup our JDBC connector to do loadbalancing and failover. For instance, setting the connector up for an Master-Slave setup (with MySQL Enterprise) is well documented, but not doing the same with MySQL Cluster.

It's not really properly documented in the manual part, but I found in the changelogs, and confirmed on IRC that to do load-balancing across the SQL nodes in MySQL Cluster, you would use a different JDBC connection string with the "loadbalance" keyword added...


jdbc:mysql:loadbalance://host-1,host-2,...host-n/database

That does indeed …

[Read more]
How to use JDBC (Connector/J) with MySQL Cluster

Last week I helped a customer setup a JBoss application against MySQL Cluster. It turns out it is not immediately obvious how you should setup our JDBC connector to do loadbalancing and failover. For instance, setting the connector up for an Master-Slave setup (with MySQL Enterprise) is well documented, but not doing the same with MySQL Cluster.

It's not really properly documented in the manual part, but I found in the changelogs, and confirmed on IRC that to do load-balancing across the SQL nodes in MySQL Cluster, you would use a different JDBC connection string with the "loadbalance" keyword added...


jdbc:mysql:loadbalance://host-1,host-2,...host-n/database

That does indeed …

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Building mysql-proxy-0.6.0 on CentOS-5.2

I recently needed to configure mysql failover on some of our test machines. Thanks to Sheeri’s helpful blog entry which provides a simple failover lua script, configuring failover is a simple matter. However, the machines are running centos-5.2 and centos doesn’t provide an rpm for mysql-proxy. This blog entry describes how to build your own.

The latest mysql-proxy (0.6.1) is apparently not backward-compatible with 0.6.0 and earlier. It incorrectly handles the case when one of the backend machines is down. Instead of just marking it as down, it errors out completely. This makes it rather difficult to use it for failover scenarios. People have complained about this for a while. Bugs 34793 and …

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MySQL Replication Tips And Tricks

Until recently, I was a student employee at the Oregon State University Open Source Lab. My career there ended, like many, with that painful process known as graduation. I got invaluable experience at the lab, not the least of which being the knowledge gained as their main (only) database administrator. One of my great pleasures in that position, was learning how to configure MySQL replication and manage clusters of replicating database servers. Even the simple case of a single master and a single slave has its edge cases.

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Showing entries 31 to 40 of 42
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