Mysql – Is MySQL Cluster just for in-memory databases

clusteringin-memory-databaseMySQL

In MySQL website I see below definition for MySQL Cluster.

MySQL Cluster is a technology that enables clustering of in-memory
databases in a shared-nothing system.

I want to use Clustering for a chat application like viber that there are some Ejabberd servers, which use MySQL as database.Is it necessary that databases use in-memory tables. according this definition all databases and tables should be in-memory or not?

This is the link of MySQL Cluster definition.

Best Answer

In NDB Cluster, data does not have be memory-resident, but I think the indexes do.

This technology is good for high availability and high activity. It is not for the typical RDBMS application.

NDB's Replication is based on "eventual consistency", where in you can do conflicting inserts/updates, but define the rules of which one wins.

While it is closely related to the rest of MySQL, NDB Cluster is not identical; there will be some coding changes if you migrate.

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Mysql – Distribute MySQL in different cities

How far apart (ping time) are the two cities? 80ms is what we experience going across the US. It is not bad.

Writing to both heads of Master-Master is possible, but has lots of pain points.

NDB Cluster allows hot-hot, but (as you say) requires some conversion.

So, back to what I see as the only viable solution: A single writable master, plus any number of slaves.

One thing that can make a remote master painful is if the user's "unit" of action translates into many SQL statements. That can/should be solved by (1) Rethink the code to use fewer statements (2) Use a Stored Procedure to encapsulate as many of the SQL statements as possible, then deploy that on the remote Master.

Reads (other than "critical reads") can/should go to a slave, behind a load balancer. And some mechanism should ensure that reads are usually "local".

Mysql – Setting up MySQL Cluster on Two Systems

Your management configuration seems fine to me. It sounds like ndb_mgmd didn't quite die or there is a problem with the contents in the /var/lib/mysql-cluster directory on the management server.

You might also want to make sure that ndb_mgmd isn't starting automatically, like through some startup script in /etc/init.d/.

To try and resolve the issue, I'd start with these steps first.

Since you are just getting started and don't have any real data yet.

Kill any left over ndb_mgmd processes with: killall ndb_mgmd or by rebooting if killall doesn't help.
Completely delete everything within /var/lib/mysql-cluster: rm -Rf /var/lib/mysql-cluster/*
Start the cluster process again: ndb_mgmd -f /etc/config.ini --initial
Verify that ndb_mgmd is listening with netstat

$> netstat -tlpn

Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:1186 0.0.0.0:* LISTEN 3251/ndb_mgmd

Connect to management node

$> ndb_mgm
ndb_mgm> show
Connected to Management Server at: localhost:1186
Cluster Configuration


[ndb_mgmd(MGM)] 1 node(s)
id=1    @192.168.9.26  (mysql-5.1.61 ndb-7.1.22)

Update

Here is a Quick Start guide from Oracle with all nodes, management, mysql and data running on one server.

http://downloads.mysql.com/tutorials/cluster/GetMySQLClusterRunning-LINUX.pdf

Best Answer

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