In Amazon space, any EC2 or Service instance can “disappear” at any time.  Depending on which service is affected, the service will be automatically restarted.  In EC2 you can choose whether an interrupted instance will be restarted, or left shutdown.

For an Aurora instance, an interrupted instance is always restarted. Makes sense.

The restart timing, and other consequences during the process, are noted in our post on Aurora Failovers.

Aurora Testing Limitations

As mentioned earlier, we love testing “uncontrolled” failovers.  That is, we want to be able to pull any plug on any service, and see that the environment as a whole continues to do its job.  We can’t do that with Aurora, because we can’t control the essentials:

• power button;
• reset switch;
…

Right now Aurora only allows a single master, with up to 15 read-only replicas.

Master/Replica Failover

We love testing failure scenarios, however our options for such tests with Aurora are limited (we might get back to that later).  Anyhow, we told the system, through the RDS Aurora dashboard, to do a failover. These were our observations:

Role Change Method

Both master and replica instances are actually restarted (the MySQL uptime resets to 0).

This is quite unusual these days, we can do a fully controlled role change in classic asynchronous replication without a restart (CHANGE MASTER TO …), and Galera doesn’t have read/write roles as such (all instances are technically writers) so it doesn’t need role changes at all.

Failover Timing

Failover between running instances takes about 30 seconds.  This is in line with information provided in the …

Our clients operate on a variety of platforms, and RDS (Amazon Relational Database Service) Aurora has received quite a bit of attention in recent times. On behalf of our clients, we look beyond the marketing, and see what the technical architecture actually delivers.  We will address specific topics in individual posts, this time checking out what the Aurora architecture means for write and caching behaviour (and thus performance).

What is RDS Aurora?

First of all, let’s declare the baseline.  MySQL Aurora is not a completely new RDBMS. It comprises a set of Amazon modifications on top of stock Oracle MySQL 5.6 and 5.7, implementing a different replication mechanism and some other changes/additions.  While we have some information (for instance from the “deep dive” by AWS VP Anurag Gupta), the source code of the Aurora modifications …

In the MySQL world, we’re used to playing in the MySQL Sandbox. It allows us to deploy a testing replication environment in seconds, without a great deal of effort or navigating multiple virtual machines. It is a tool that we couldn’t live without in Support.

In this post I am going to walk through the different ways we have to deploy a MongoDB replica/sharding set test in a similar way. It is important to mention that this is not intended for production, but to be used for troubleshooting, learning or just playing around with replication.

Replica Set regression test’s diagnostic commands

MongoDB includes a .js that allows us to deploy a replication set from the MongoDB’s shell. Just run the following:

# mongo --nodb …

Emphasis on clustering solutions comes up quite a lot when talking to customers about High Availability. The reason is because clustering is supposed to provide an easier solution for maintaining high availability and so that you do not have to rely on other tools and techniques outside of the database server. I thought it would be good to share the gist of many of my discussions around clustering, in the form of a blog post. So here I will be doing a high-level comparison between MySQL NDB Cluster and Percona XtraDB Cluster.

The post Percona XtraDB Cluster – A Drop-in-place Clustering Solution for MySQL appeared first on ovais.tariq.

Read the original article at MySQL requires an authoritative master to build slaves

In MySQL database operations, you often need to rebuild slaves. They fail for a lot of different reasons, fall out of sync or crash. When this happens you may find you need to reclone and start fresh. This is normally done by finding your authoritative master database, and doing a hotbackup. Click through to the [...]

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