---
title: "MariaDB Galera Cluster: A Quirk of Bootstrapping"
publish_date: 2015-03-19
updated_date: 2019-08-20
author: "Geoff Montee"
---

# MariaDB Galera Cluster: A Quirk of Bootstrapping

![MariaDB Galera Cluster: A Quirk of Bootstrapping](/sites/default/files/inline-images/boots.png)MariaDB Galera Cluster is part of the easily deployed High Availability product [MariaDB Enterprise Cluster](https://staging-mdb.com/products/mariadb-enterprise-cluster "MariaDB Enterprise Cluster"). This blog raises a question about the behaviour of the bootstrapping method.

## Old Bootstrapping Method

When Galera was first released, the usual method used to bootstrap a cluster was to set [wsrep\_cluster\_address](https://staging-mdb.com/kb/en/mariadb/galera-cluster-system-variables/#wsrep_cluster_address "wsrep_cluster_address") to *‘gcomm://’*. With no other node addresses specified in *wsrep\_cluster\_address*, the node would form its own cluster:

```
[gmontee@localhost ~]$ sudo service mysql start --wsrep_cluster_address='gcomm://'
Starting MySQL....                                         [  OK  ]
[gmontee@localhost ~]$ mysql -u root --execute="SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');"
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_cluster_size   | 1       |
| wsrep_cluster_status | Primary |
| wsrep_connected      | ON      |
| wsrep_ready          | ON      |
+----------------------+---------+

```

## Newer Bootstrapping Method

A while ago, the old bootstrapping method was replaced with the *bootstrap* option to the mysql.server init script:

```
[gmontee@localhost ~]$ sudo service mysql bootstrap
Bootstrapping the cluster.. Starting MySQL....             [  OK  ]
[gmontee@localhost ~]$ mysql -u root --execute="SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');"
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_cluster_size   | 1       |
| wsrep_cluster_status | Primary |
| wsrep_connected      | ON      |
| wsrep_ready          | ON      |
+----------------------+---------+

```

This newer bootstrapping method was enabled by the [–wsrep-new-cluster](https://staging-mdb.com/kb/en/mariadb/mysqld-options/#wsrep-new-cluster "--wsrep-new-cluster") command-line option. The *bootstrap* option of the init script passes this option to *mysqld* under the hood. Explicitly starting the server with this option is equivalent to using the *bootstrap* option:

```
[gmontee@localhost ~]$ sudo service mysql start --wsrep-new-cluster
Starting MySQL....                                         [  OK  ]
[gmontee@localhost ~]$ mysql -u root --execute="SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');"
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_cluster_size   | 1       |
| wsrep_cluster_status | Primary |
| wsrep_connected      | ON      |
| wsrep_ready          | ON      |
+----------------------+---------+

```

The newer bootstrapping method is more user-friendly. The name of the option matches its intended use (bootstrapping a new cluster), which is more intuitive than overriding *wsrep\_cluster\_address*.

## A quirk of the new method

Because the new node is forming a new cluster on its own, you may think that you don’t have to specify a value of *wsrep\_cluster\_address* at all when you use the newer bootstrapping method. Why should the node need to know what other addresses are in the cluster? It will be the only one!

However, this is not true!

```
[gmontee@localhost ~]$ sudo service mysql start --wsrep-new-cluster --wsrep_cluster_address=''
Starting MySQL....                                         [  OK  ]
[gmontee@localhost ~]$ mysql -u root --execute="SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');"
+----------------------+--------------+
| Variable_name        | Value        |
+----------------------+--------------+
| wsrep_cluster_size   | 0            |
| wsrep_cluster_status | Disconnected |
| wsrep_connected      | OFF          |
| wsrep_ready          | OFF          |
+----------------------+--------------+

```

Not setting *wsrep\_cluster\_address* or setting it to the empty string has a [special meaning](https://github.com/MariaDB/server/blob/75a27eeaf7a0bcdd3888e1bbaf5d55c573d7696b/sql/wsrep_mysqld.cc#L933): it waits for *wsrep\_cluster\_address* to be set dynamically. Only after it’s set does WSREP get initialized.

```
[gmontee@localhost ~]$ mysql -u root --execute="SET GLOBAL wsrep_cluster_address='gcomm://';"
[gmontee@localhost ~]$ mysql -u root --execute="SHOW GLOBAL STATUS WHERE Variable_name IN ('wsrep_ready', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected');"
+----------------------+---------+
| Variable_name        | Value   |
+----------------------+---------+
| wsrep_cluster_size   | 1       |
| wsrep_cluster_status | Primary |
| wsrep_connected      | ON      |
| wsrep_ready          | ON      |
+----------------------+---------+

```

## Final Thoughts

Considering that *wsrep\_cluster\_address* is listed as a [mandatory option](https://staging-mdb.com/kb/en/mariadb/getting-started-with-mariadb-galera-cluster/#mandatory-settings "mandatory option"), this behavior shouldn’t be too surprising. However, it is a bit unintuitive.

Has anyone else been confused by this behavior in the past?