I'm running into an issue with the way Galera cluster is set up to work with MariaDB.
Each node in the cluster has to have a configuration that houses the IP addresses of every other node (inclusive) in the cluster. If I ever want to add a node to the cluster, I have to manually add that node's IP address to the configurations on every other node.
This makes spinning up and down servers dynamically for the cluster difficult.
Are there any work arounds for this? Possibly a way to notify every node of a new node being added to the cluster remotely?
Galera clusters only need one server working as a master node. You can use any or all of the servers in the cluster as the cluster address for the new node and the new node will automatically connect to the rest of the nodes.
Example
Active Cluster:
10.0.0.2 (the first node of the galera cluster)
10.0.0.3
10.0.0.4
If we want to add 10.0.0.5 to the cluster, we can use any of the following as a cluster address for it:
gcomm://10.0.0.2
gcomm://10.0.0.3
gcomm://10.0.0.4
gcomm://10.0.0.2,10.0.0.3
gcomm://10.0.0.2,10.0.0.4
gcomm://10.0.0.3,10.0.0.4
gcomm://10.0.0.2,10.0.0.3,10.0.0.4
The down side to this is that the new node would lose the other servers as fall back if the ones that they have configured in their cluster address are down.
So a work around for this is to have X number of static nodes that will never go down, then use all of those as the cluster addresses for any new slaves that you bring up.
Related
I have already setup properly 3 node (mariadb) Galera cluster with maxscale load balancing. maxscale is on different server.
All the nodes are Primary component. I want to test the non-primary component situation. How can I create this situation in my Galera cluster.
I stopped one by one all the servers and started again one by one but all the nodes are in sync when they are started back.
How can I test the non-primary state of a node.
Add a 4th node and make it a Replica only, not a Primary. And don't tell maxscale to allow writes to it.
I have a Mariadb Galera cluster with 2 nodes and it is up and running.
Before moving to production, I want to make sure that if a node crashes abruptly, It should come up on its own.
I tried using systemd "restart", but after killing the mysql process the mariadb service does not come up, so, is there any tool or method, that I can use to automate bringing up the nodes after crashes?
Galera clusters needs to have quorum (3 nodes).
In order to avoid a split-brain condition, the minimum recommended number of nodes in a cluster is 3. Blocking state transfer is yet another reason to require a minimum of 3 nodes in order to enjoy service availability in case one of the members fails and needs to be restarted. While two of the members will be engaged in state transfer, the remaining member(s) will be able to keep on serving client requests.
You can read more here.
I have a galera cluster of three nodes, If I shut down the the three virtual machines and started them all at once, systemd will automatically start mariadb on each of the virtual machines.
Some times it happens that all of the mariadb instances start at once, and this result of a broken cluster.
Which I have to reinitiate using galera_new_cluster
The question is, why does starting all the mariadb instances at once break the cluster ?
Thank you
Whenever you start a node, it either starts as the first node in the cluster (initiates a new cluster), or it attempts to connect to an existing nodes using wsrep_cluster_address. The behavior depends on the node options.
So, every time when you shut down or lose all nodes and start them again, there is nothing to connect to, and you need to start a new cluster. galera_new_cluster does that by starting a node with --wsrep-new-cluster option which overrides the current value of wsrep_cluster_address.
If sometimes it works for you automatically, it most likely means that one of your nodes is permanently configured as the "first node", either via wsrep_cluster_address=gcomm://, or via wsrep-new-cluster. It is a wrong setup in itself. If you lose or shut down only this node and have to restart it, it won't join the remaining nodes in the cluster, it will create a new one.
When you start all nodes at once, you create a race condition. If your "first node" comes up first and initializes quickly enough, it will create a new cluster, and other nodes will join it. If another node comes up first, it won't be able to join anything, thus you get a "broken cluster".
You can find more information on restarting the whole cluster here:
http://galeracluster.com/documentation-webpages/restartingcluster.html
Recommendate way of bootstrapping cluster is to start a advanced node first then second and third so for you need to check lsn no of all nodes or check grastate.date file where you can check all nodes value .
so follow these steps your cluster node will not be crash
I would like to synchronize only some databases on a cluster, with replicate-do-db.
→ If I use the Galera cluster, are all data sent over the network, or are nodes smart enough to only fetch their specific databases?
On "classic" master/slave MariaDB replication, filters are made by the slave, causing network charge for nothing if you don't replicate that database. You have to configure a blackhole proxy to filter binary logs to avoid this (setup example), but the administration after is not really easy. So it would be perfect with a cluster if I can perform the same thing :)
binlog_... are performed in the sending (Master) node.
replicate_... are performed in the receiving (Slave) node.
Is this filtered server part of the cluster? If so, you are destroying much of the beauty of Galera.
On the other hand, if this is a Slave hanging off one of the Galera nodes and the Slave does not participate in the "cluster", this is a reasonable architecture.
Suppose that we have two application servers(app1 and app2) and also we setup multi master MariaDB clustering with two nodes(node1 and node2) without any HAProxy.Can we connect app1 to node1 and app2 to node2 and also both of app1 and app2 write to node1 and node2?
Does it cause any conflict?
Galera solves most of the problems that occur with Master-Master:
If one of Master-Master dies, now what? Galera recovers from any of its 3 nodes failing.
If you INSERT the same UNIQUE key value in more than one Master, M-M hangs; Galera complains to the last client to COMMIT.
If a node dies and recovers, the data is automatically repaired.
You can add a node without manually doing the dump, etc.
etc.
However, there are a few things that need to be done differently to when using Galera: Tips