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Showing entries 1 to 30 of 32 Next 2 Older Entries

Displaying posts with tag: failover (reset)

Geographically distributed multi-master MySQL clusters
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In this webinar, we discuss the multi-master capabilities of Continuent Tungsten to help you build and manage systems that spread data across multiple sites.  We cover important topics such as setting up large scale topologies, handling failures, and how to handle data privacy issues like removing personally identifiable information or handling privacy law restrictions on data movement. We
Auto failover of mysql master in mysql multi-master multi-slave cluster
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This post is an extension to my earlier posts about multi master replication cluster multi master replication in mysql and mysql multi master replication act II The problem I had encountered and discussed was with automatic failover. What happens when the master goes down? How can either a slave or another master be promoted to become the master? Once the settings are done on all the mysql dbs
MySQL Cluster on Raspberry Pi - Sub-second failover
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MySQL Cluster claims to achieve sub-second failover without any data loss for commited transactions. And I always wanted to show this in a demo. Now we created that demo finally. See Mark's blog and Keith's blog for setting up MySQL Cluster on RaspberryPi.
The nice thing about the RPis is that you can easily pull the plug to test failover. Ok, that is only one possible failure scenario but for sure the most obvious and more impressive than "kill -9".


That demo application is constantly using the database for storing new lines, removing old lines and reading all line data for the graphical view. There is no caching. It uses JDBC directly.
To document the setup here is the config.ini file




  [Read more...]
Failover Techniques for MySQL
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The occurrence of failures and crashes can compromise the high availability of your database system affecting your revenue and reputation. Therefore, it is fundamental to minimize downtime and have an efficient strategy for crash recovery.

Replication and failover are commonly applied to deal with those situations. However, other types of failures can also affect the recovery process. In fact, the occurrence of unanticipated faults can really be an headache! Thus, it is better to be prepared and implement a good fault-tolerant failover strategy.

Performing failover is not trivial. It requires the execution of several steps in order to ensure data consistency (i.e., no data loss) -- especially if the "best" candidate to become the new master is not the most up-to-date.

Note that, one might desire that the slave with the best hardware





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PoC: Using a Group Communication System (Isis2) to improve MySQL Replication HA
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Modern NoSQL solutions make good, old MySQL Replication appear weak on High Availability (HA). Basically, MySQL users have three choices for MySQL Replication HA: give up on HA, believe that doubling single points of failures means HA, or go for a proper but complex solution. Albeit, as NoSQL world and competition proves, solid HA can be dead simple: embed a Group Communication System (GCS) into MySQL! No single point of failure and near zero client deployment is doable. In parts, the proposal surpassed Pacemaker/Corosync. Read on: story, slides, experimental code.

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Tungsten University: Unleashing the Power of Tungsten Connectors
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How To Configure Tungsten Connector For Load Balancing, Read/Write Splitting, Automatic Failover And Online Maintenance
MySQL Load Balancing, Read/Write Splitting, Automatic Failover And Online Maintenance
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How To Configure Tungsten Connector For Load Balancing, Read/Write Splitting, Automatic Failover And Online Maintenance  Tungsten clusters use the Tungsten Connector to ensure your applications transparently connect to the master. This enables fail over and seamless switching of masters for online maintenance. However, you can do far more. Tungsten Connector allows you to make better use of
Tungsten University: Configure & provision Continuent Tungsten clusters
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Are you unsure of the steps needed to get your Continuent Tungsten cluster up-and-running? In this virtual course, we will teach you how to get from a single database server to a scalable cluster, or from a brittle MySQL replication system to a transparent, manageable Tungsten cluster.  We will discuss the benefits of leveraging Continuent Tungsten clustering with MySQL, and walk you through the
Webinar Monday, Nov 5th @ 15:00 GMT - MySQL High Availability Realized
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High Availability (HA) ensures all important business information is available for your application even when there is no database failure. This includes: How about when you are upgrading your database schema? What if you need to add memory to a database server or reconfigure/restart MySQL? If your apps want to read data from a MySQL slave, how can you be sure they are not reading stale data
Haute disponibilité MySQL, par Continuent
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La haute disponibilité, c’est garantir aux applications un accès permanent aux données, même en cas de panne. Permanent ? Même lorsque vous mettez à jour le schéma de vos bases ? Que vous ajoutez de la RAM sur un serveur ? Que vous reconfigurez ou redémarrez MySQL ?    Comment lire les données depuis un nœud esclave avec une garantie que les données sont à jour, sans changement applicatif ?
Webinar 10/11: Multi-Master, Multi-Site MySQL Databases Made Easy with Continuent Tungsten
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Cross-site databases are the next challenge facing today's MySQL-based businesses. Continuent Tungsten provides multiple options for spreading data across sites, including primary/DR, multi-master, and system-of-record approaches. Join us to learn how Continuent Tungsten enables replication, failover, and routing of transactions between sites. We cover the following topics: Introduction to
Replication and auto-failover made easy with MySQL Utilities
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If you’re a user of MySQL Workbench then you may have noticed a pocket knife icon appear in the top right hand corner – click on that and a terminal opens which gives you access to the MySQL utilities. In this post I’m focussing on the replication utilities but you can also refer to the full MySQL Utilities documentation.

What I’ll step through is how to uses these utilities to:

  • Set up replication from a single master to multiple slaves
  • Automatically detect the failure of the master and promote one of the slaves to be the new master
  • Introduce the old master back into the topology as a new slave and
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Automated MySQL Master Failover
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After the GitHub MySQL Failover incident a lot of blogs/people have explained that fully automated failover might not be the most optimal solution.

Fully automated failover is indeed dangerous, and should  be avoided if possible. But a complete manual failover is also dangerous. A fully automated manually triggered failover is probably a better solution.

A synchronous replication solution is also not a complete solution. A split-brain situation is a good example of a failure which could happen. Of course most clusters have all kinds of safe guard to prevent that, but unfortunately also safe guards can fail.

Every failover/cluster should be considered broken unless:
  • You've tested the failover scripts and procedures
  • You've tested the failover scripts and procedures under normal load
  • You've tested the failover scripts







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    Controlled failover simplicity with MySQL
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    As part of a recent engagement, I described the relative products to manage a MySQL pair (i.e. an Active/Passive MySQL masters configuration). This included the steps to undertake a controlled failover for supporting software maintenance using manual procedures. The upcoming Effective MySQL: Replication Techniques in Depth book details each step and all conditions to review over a dozen pages. While the steps are straightforward and generally well known, scripting this for your environment takes a certain amount of work to ensure your information is correct, and application connectivity loss is kept to a minimum.

    In Continuent Tungsten (which I have just been reviewing these past few weeks), I achieved the same result with a single command.

    $ echo "switch" |
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    New MySQL 5.6 Replication Utilities – mysqlfailover and mysqlrpladmin
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    With all of the new news coming out right now, it can be easy to miss or overlook some of the new features.

    While there’s been a lot of talk about MySQL 5.6 Replication, I specifically wanted to mention the new ‘mysqlfailover’ and ‘mysqlrpladmin’ utilities.

    These are two new MySQL replication utilities (results of the new Global Transaction Identifiers (GTIDs) in MySQL 5.6).

    Let me quote the MySQL 5.6 Replication article for both of these utilities:

    mysqlfailover

    “Provides continuous monitoring of the replication topology, enabling failover to a slave in the event of an outage on the master.

    The default behavior is to

      [Read more...]
    Multi-Site, Multi-Master MySQL Databases Made Easy with Tungsten - Webinar 9/22
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    Cross-site databases are the next challenge facing today's MySQL-based businesses. Continuent Tungsten enables multi-master with an innovative new architecture called System of Record that avoids data conflicts, ensures sites are ready for quick failover, and uses hardware resources efficiently.Watch this video from our 9/22/11 webcast to learn how Tungsten Enterprise enables System of Record
    Howto setup MySQL on a DRBD volume
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    One more DRBD tutorial, this time I will describe howto setup MySQL with DRBD (Distributed Replicated Block Device). Purpose This document describes how to to setup a failover system with MySQL and DRBD (Distributed Replicated Block Device). Introduction In this tutorial we will setup two Debian Linux nodes with a DRBD volume. MySQL will be [...]
    Cache pre-loading on mysqld startup
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    The following quirky dynamic SQL will scan each index of each table so that they’re loaded into the key_buffer (MyISAM) or innodb_buffer_pool (InnoDB). If you also use the PBXT engine which does have a row cache but no clustered primary key, you could also incorporate some full table scans. To make mysqld execute this on startup, create /var/lib/mysql/initfile.sql and make it be owned by mysql:mysql
    SET SESSION group_concat_max_len=100*1024*1024;
    SELECT GROUP_CONCAT(CONCAT('SELECT COUNT(`',column_name,'`) FROM `',table_schema,'`.`',table_name,'` FORCE INDEX (`',index_name,'`)') SEPARATOR ' UNION ALL ') INTO @sql FROM information_schema.statistics WHERE table_schema NOT IN ('information_schema','mysql') AND seq_in_index = 1;
    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
    SET SESSION group_concat_max_len=@@group_concat_max_len;
    
    and in my.cnf add a line  [Read more...]
    Quest for Resilience: Multi-DC Masters
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    This is a Request for Input. Dual MySQL masters with MMM in a single datacentre are in common use, and other setups like DRBD and of course VM/SAN based failover solutions are conceptually straightforward also. Thus, achieving various forms of resilience within a single data-centre is doable and not costly.

    Doing the same across multiple (let’s for simplicity sake limit it to two) datacentres is another matter. MySQL replication works well across longer links, and it can use MySQL’s in-built SSL or tools like stunnel. Of course it needs to be kept an eye on, as usual, but since it’s asynchronous the latency between the datacentres is not a big issue (apart from the fact that the second server gets up-to-date a little bit later).

    But as those who have tried will know, having a client (application server) connection to a MySQL instance in a remote data-centre

      [Read more...]
    Installing MEM agent on a cluster on the logical host
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    The goal is to have only one entry in the Enterprise Monitor Dashboard that shows the status of the MySQL instance, no matter on which physical server in runs. There are two ways to achieve this:
    • You can install the agent on both physical nodes
    • You can install the agent on a shared storage.
    In either case you have to make sure, that only one agent runs at a time. You have to integrate the agent into your cluster framework. I will not describe how this works, as it is highly dependant on your cluster framework.
    The following description assumes, that you will install the agent on both physical nodes.
  • Install the agent but DO NOT START the agent yet.

  • Edit the [agent-installdir]/etc/mysql-monitor-agent.ini
    In the [mysql-proxy] section add the following line:
    agent-host-id=[logical





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    Installing MEM agent in a cluster on the physical hosts
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    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  [Read more...]
    MySQL University session Oct 22: Dual Master Setups With MMM
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    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


      [Read more...]
    Dogfood: making our systems more resilient
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    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

      [Read more...]
    Failure scenarios and solutions in master-master replication
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    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.  [Read more...]
    More information about running MySQL on Open HA Cluster / Solaris Cluster
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    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



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



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



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



      [Read more...]
    Building mysql-proxy-0.6.0 on CentOS-5.2
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    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

      [Read more...]
    MySQL Replication Tips And Tricks
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    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.

    read more

    Showing entries 1 to 30 of 32 Next 2 Older Entries

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