If a specific node in your cluster is acting as the primary node by receiving all of the application's write traffic, then this node should not usually be used as the donor node, because the system-wide lock could interfere with the application. In this case, you can define one or more preferred donor nodes by setting the wsrep_sst_donor system variable.
Enabling Percona XtraDB Cluster SST Traffic Encryption
The replication traffic encryption cannot be enabled on a running cluster. Ifit was disabled before the cluster was bootstrapped, the cluster must tostopped. Then set up the encryption, and bootstrap (see Bootstrapping the First Node)again.
Previously, we discussed how to set up MariaDB Galera multi-master cluster on Ubuntu. By default, replication traffic in MariaDB Galera cluster is unencrypted. This tutorial will be showing you how to Enable TLS encryption so nodes in the cluster can communicate with each other securely over the public Internet. There are 2 types of replication traffic in Galera cluster:
I hope this tutorial helped you encrypt replication traffic in MariaDB Galera cluster. In the next tutorial, we will see how to combine master-slave replication with MariaDB Galera cluster. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks. Take care ?
The previous SSL methods (encrypt=2 and encrypt=3), are based on socat usage, -unreach.org/socat/doc/socat-openssltunnel.html. The certs are not built the same way as the certs created by MySQL (for encryption of client communication with MySQL). To simplify SSL configuration and usage, we added a new encryption method (encrypt=4) so that the SSL files generated by MySQL can now be used for SSL encryption of SST traffic.
In this tutorial, we will install and configure a cluster of database servers, running Percona XtraDB (Percona is a fully compatible, drop-in replacement for MySQL), version 5.7, and HAProxy high availability load balancing proxy server which will handle all the traffic directed to the database nodes.
And VOILA! Believe it or not, you now have a working High Availability MySQL database cluster, working on three nodes, with a HAProxy load balancer taking care of the load, checking nodes health, directing traffic to appropriate place! Happy querying. :-)
Garbd can be installed on smaller nodes, even virtual servers. It does not require powerful hardware, it does not store any data nor apply any of the writesets. But it does see all the replication traffic, and takes part in the quorum calculation. Thanks to it, you can deploy setups like four nodes, two per DC + garbd in the third one - you have five nodes in total, and such cluster can accept up to two failures. So it means it can accept a full shutdown of one of the datacenters.
Preventing people from accessing configuration and log files is one thing. The other issue is to make sure data is securely transferred over the network. With an exception of setups where all the clients are local and use Unix socket to access MySQL, in majority of cases, data which forms a result set for a query, leaves the server and is transferred to the client over the network. Data can also be transferred between MySQL servers, for example via standard MySQLreplication or within a Galera cluster. Network traffic can be sniffed, and through those means, your data would be exposed.
To prevent this from happening, it is possible to use SSL to encrypt traffic, both server and client-side. You can create an SSL connection between a client and a MySQL server. You can also create an SSL connection between your master and your slaves, or between the nodes of a Galera cluster. This will ensure that all data that is transferred is safe and cannot be sniffed by an attacker who gained access to your network.
The MySQL documentation covers in detail how to setup SSL encryption. If you find it too cumbersome, ClusterControl can help you deploy a secure environment for MySQL replication or Galera cluster in a couple of clicks:
Enabling encryption for Galera means IST will also be encrypted because the communication happens via the same socket. SST, on the other hand, has to be configured separately as shown in the next section. All nodes in the cluster must be enabled with SSL encryption and you cannot have a mix of nodes where some have enabled SSL encryption, and others not. The best time to configure this is when setting up a new cluster. However, if you need to add this on a running production system, you will unfortunately need to rebootstrap the cluster and there will be downtime.
All Galera nodes in the cluster must use the same key, certificate and CA (optional). You could also use the same key and certificate created for MySQL client-server encryption, or generate a new set for this purpose only. To activate encryption inside Galera, one has to append the option and value under wsrep_provider_options inside the MySQL configuration file on each Galera node. For example, consider the following existing line for our Galera node:
The equivalent Web-based, out of the box solution to manage and monitor Galera Cluster is ClusterControl. It provides a web-based interface to deploy clusters, monitors key metrics, provides database advisors, and take care of management tasks like backup and restore, automatic patching, traffic encryption and availability management.
A cluster is considered operational if all nodes or majority of the nodes are online. Online means they are able to see each other through Galera's replication traffic or group communication. If no traffic is coming in and out from the node, the cluster will send a heartbeat beacon for the node to response in a timely manner. Otherwise, it will be put into the delay or suspected list according to how the node responses.
Setting up a replication slave is not very complex but it still can be tricky if you are not proficient with MySQL and tools like xtrabackup. The whole process would consist of setting up the repository on a new server and installing the MySQL database. Then you will have to provision that host using data from Galera cluster. You can use xtrabackup for that but other tools like mydumper/myloader or even mysqldump will work as well (as long as you execute them correctly). Once the data is there, you will have to setup the replication between a master Galera node and the replication slave. Finally, you would have to reconfigure your proxy layer to include the new slave and route the traffic towards it or make tweaks in how your application connects to the database in order to redirect some of the load to the replication slave.
The problem was related to the fact that instructions did not mention any file except for /etc/mysql/my.cnf where, in fact, we should have been modifying /etc/mysql/percona-xtradb-cluster.conf.d/wsrep.cnf. That file contained empty variable:
If we look at the outage, the cluster was unavailable for a few minutes thanks to ProxySQL sending all traffic to a single node. But according to the definition of high availability, a single node is not HA. So if we take into account that we need at least two nodes to be available, the recovery happens only after the first SST has completed. This means our Mean Time To Recover Service (MTTRS) on Galera was at least 4 hours! 2ff7e9595c
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