MariaDB Galera Cluster provides high availability with synchronous replication, while adding asynchronous replication boosts redundancy for disaster recovery or reporting.
and MariaDB Galera Cluster can be used together. However, there are some things that have to be taken into account.
If you want to use and MariaDB Galera Cluster together, then the following tutorials may be useful:
If a Galera Cluster node is also a , then some additional configuration may be needed.
Like with , write sets that are received by a node with are not written to the by default.
If the node is a replication master, then its replication slaves only replicate transactions that are in the binary log, so this means that the transactions that correspond to Galera Cluster write-sets would not be replicated by any replication slaves by default. If you would like a node to write its replicated write sets to the , then you will have to set . If the node has any replication slaves, then this would also allow those slaves to replicate the transactions that corresponded to those write sets.
See for more information.
If a Galera Cluster node is also a , then some additional configuration may be needed.
If the node is a replication slave, then the node's will be applying transactions that it replicates from its replication master. Transactions applied by the slave SQL thread will only generate Galera Cluster write-sets if the node has set. Therefore, in order to replicate these transactions to the rest of the nodes in the cluster, must be set.
If the node is a replication slave, then it is probably also a good idea to enable . When this is enabled, the node will restart its whenever it rejoins the cluster.
Historically, Galera Cluster nodes acting as asynchronous replication slaves were restricted to single-threaded execution (slave_parallel_threads=0). Enabling parallel replication often resulted in deadlocks due to conflicts between ordering and Galera's internal pre-commit ordering.
As of MariaDB 12.1.1, this limitation has been resolved.
On supported versions, you can safely configure slave_parallel_threads to a value greater than 0 to improve the performance of incoming replication streams.
Recommended Configuration (MariaDB 12.1.1+):
Both and support , so extra caution must be taken when using all of these features together. See for more details on how MariaDB Galera Cluster interprets replication filters.
It is most common to set to the same value on each node in a given cluster. Since uses a , all nodes should have the same data, so in a logical sense, a cluster can be considered in many cases a single logical server for purposes related to . The of each cluster node might even contain roughly the same transactions and if is set and if is enabled and if non-Galera transactions are not being executed on any nodes.
There are cases when it might make sense to set a different value on each node in a given cluster. For example, if is set and if another cluster or a standard MariaDB Server is using to replicate transactions from each cluster node individually, then it would be required to set a different value on each node for this to work.
Keep in mind that if replication is set up in a scenario where each cluster node has a different value, and if the replication topology is set up in such a way that a cluster node can replicate the same transactions through Galera and through MariaDB replication, then you may need to configure the cluster node to ignore these transactions when setting up MariaDB replication. You can do so by setting to the server IDs of all nodes in the same cluster when executing . For example, this might be required when circular replication is set up between two separate clusters, and each cluster node has a different value, and each cluster has set.
This page is licensed: CC BY-SA / Gnu FDL
MariaDB's are very useful when used with , which is primarily what that feature was developed for. , on the other hand, was developed by Codership for all MySQL and MariaDB variants, and the initial development of the technology pre-dated MariaDB's implementation. As a side effect, (at least until ) only partially supports MariaDB's implementation.
Galera Cluster has its own that is substantially different from . However, it would still be beneficial if was able to associate a Galera Cluster write set with a that is globally unique but that is also consistent for that write set on each cluster node.
MariaDB supports wsrep_gtid_mode.
MariaDB has a feature called wsrep GTID mode. When this mode is enabled, MariaDB uses some tricks to try to associate each Galera Cluster write set with a that is globally unique, but that is also consistent for that write set on each cluster node. These tricks work in some cases, but can still become inconsistent among cluster nodes.
Several things need to be configured for wsrep GTID mode to work, such as
wsrep_gtid_mode=ON needs to be set on all nodes in the cluster.
wsrep_gtid_domain_id needs to be set to the same value on all nodes in a given cluster, so that each cluster node uses the same domain when assigning for Galera Cluster's write sets. When replicating between two clusters, each cluster should have this set to a different value, so that each cluster uses different domains when assigning for their write sets.
needs to be enabled on all nodes in the cluster. See MDEV-9855.
needs to be set to the same path on all nodes in the cluster. See .
And as an extra safety measure:
should be set to a different value on all nodes in a given cluster, and each of these values should be different than the configured wsrep_gtid_domain_id value. This is to prevent a node from using the same domain used for Galera Cluster's write sets when assigning for non-Galera transactions, such as DDL executed with wsrep_sst_method=RSU set or DML executed with wsrep_on=OFF set.
If you want to avoid writes accidentally local GTIDS, you can avoid it with by setting this:
In this case you get an error:
You can overwrite it temporarily with:
For information on setting , see Using MariaDB Replication with MariaDB Galera Cluster: Setting server_id on Cluster Nodes.
If a Galera Cluster node is also a , then that node's will be applying transactions that it replicates from its replication master. If the node has set, then each transaction that the applies will also generate a Galera Cluster write set that is replicated to the rest of the nodes in the cluster.
The node acting as slave includes the transaction's original Gtid_Log_Event in the replicated write set, so all nodes should associate the write set with its original GTID. See MDEV-13431.
This page is licensed: CC BY-SA / Gnu FDL
can be used for replication between two MariaDB Galera Clusters. This article will discuss how to do that.
Before we set up replication, we need to ensure that the clusters are configured properly. This involves the following steps:
Set on all nodes in both clusters. See Configuring MariaDB Galera Cluster: Writing Replicated Write Sets to the Binary Log and Using MariaDB Replication with MariaDB Galera Cluster: Configuring a Cluster Node as a Replication Master for more information on why this is important. This is also needed to .
Set to the same value on all nodes in a given cluster, but be sure to use a different value in each cluster. See for more information on what this means.
If you want to use replication, then you also need to configure some things to . For example:
needs to be set on all nodes in each cluster.
needs to be set to the same value on all nodes in a given cluster so that each cluster node uses the same domain when assigning for Galera Cluster's write sets. Each cluster should have this set to a different value so that each cluster uses different domains when assigning for their write sets.
needs to be enabled on all nodes in the cluster. See about that.
And as an extra safety measure:
should be set to a different value on all nodes in a given cluster, and each of these values should be different than the configured value. This is to prevent a node from using the same domain used for Galera Cluster's write sets when assigning for non-Galera transactions, such as DDL executed with set or DML executed with set.
To improve the performance of the replication stream between clusters, it is recommended to enable on the nodes in the destination cluster (the cluster acting as the replica).
Our process to set up replication is going to be similar to the process described at , but it will be modified a bit to work in this context.
You can also set up between the two clusters, which means that the second cluster replicates from the first cluster, and the first cluster also replicates from the second cluster.
wsrep_mode = DISALLOW_LOCAL_GTID ERROR 4165 (HY000): Galera replication not supportedSET sql_log_bin = 0;SET GLOBAL slave_parallel_threads = 4; -- Adjust based on workload
SET GLOBAL slave_parallel_mode = 'optimistic';Now that the backup has been restored to the second cluster's replica, you can start the server by bootstrapping the node.
At this point, you need to get the replication coordinates of the primary from the original backup.
The coordinates will be in the file.
mariadb-backup dumps replication coordinates in two forms: and file and position coordinates, like the ones you would normally see from output. In this case, it is probably better to use the coordinates.
For example:
Regardless of the coordinates you use, you will have to set up the primary connection using and then start the replication threads with .
If you want to use GTIDs, then you will have to first set to the coordinates that we pulled from the file, and we would set MASTER_USE_GTID=slave_pos in the command. For example:
If you want to use the file and position coordinates, then you would set MASTER_LOG_FILE and MASTER_LOG_POS in the command to the file and position coordinates that we pulled the file. For example:
If the replica is replicating normally, then the next step would be to start the MariaDB Server process on the other nodes in the second cluster.
Now that the second cluster is up, ensure that it does not start accepting writes yet if you want to set up between the two clusters.
How this is done would depend on whether you want to use the coordinates or the file and position coordinates.
Regardless, you need to ensure that the second cluster is not accepting any writes other than those that it replicates from the first cluster at this stage.
To get the GTID coordinates on the second cluster, you can check by executing:
Then on the first cluster, you can set up replication by setting to the GTID that was returned and then executing :
To get the file and position coordinates on the second cluster, you can execute :
Then on the first cluster, you would set master_log_file and master_log_pos in the command. For example:
$ mariadb-backup --backup \
--target-dir=/var/mariadb/backup/ \
--user=mariadb-backup --password=mypassword$ mariadb-backup --prepare \
--target-dir=/var/mariadb/backup/$ rsync -avrP /var/mariadb/backup c2dbserver:/var/mariadb/backup$ mariadb-backup --copy-back \
--target-dir=/var/mariadb/backup/$ chown -R mysql:mysql /var/lib/mysql/CREATE USER 'repl'@'c2dbserver1' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'c2dbserver1';SHOW SLAVE STATUS\GSHOW GLOBAL VARIABLES LIKE 'gtid_current_pos';SET GLOBAL gtid_slave_pos = "0-1-2";
CHANGE MASTER TO
MASTER_HOST="c2dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_USE_GTID=slave_pos;
START SLAVE;SHOW SLAVE STATUS\GSET GLOBAL slave_parallel_threads = 4; -- Adjust based on workload
SET GLOBAL slave_parallel_mode = 'optimistic';CREATE USER 'repl'@'c1dbserver1' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'c1dbserver1';mariadb-bin.000096 568 0-1-2SET GLOBAL gtid_slave_pos = "0-1-2";
CHANGE MASTER TO
MASTER_HOST="c1dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_USE_GTID=slave_pos;
START SLAVE;CHANGE MASTER TO
MASTER_HOST="c1dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_LOG_FILE='mariadb-bin.000096',
MASTER_LOG_POS=568,
START SLAVE;SHOW MASTER STATUSCHANGE MASTER TO
MASTER_HOST="c2dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_LOG_FILE='mariadb-bin.000096',
MASTER_LOG_POS=568;
START SLAVE;Hybrid replication leverages standard, asynchronous MariaDB Replication to copy data from a synchronous MariaDB Galera Cluster to an external server or another cluster. This configuration establishes a one-way data flow, where the entire Galera Cluster serves as the source (primary) for one or more asynchronous replicas. This advanced setup combines the strengths of both replication methods: synchronous replication ensures high availability within the primary site, while asynchronous replication caters to specific use cases, allowing for flexible data distribution.
Implementing a hybrid replication setup is a powerful technique for solving several common business needs:
Before implementing a hybrid setup, it is critical to understand the technical challenges:
This page is licensed: CC BY-SA / Gnu FDL
Disaster Recovery (DR)
Galera Cluster provides high availability and automatic failover. Use asynchronous replication for a distant replica, promoting it during site outages.
Feeding Analytics/BI Systems
Replicate from OLTP Galera Cluster to a data warehouse or analytics server to run heavy queries without affecting production performance.
Upgrades and Migrations
Use an asynchronous replica to test new MariaDB versions or migrate to new hardware with minimal downtime.
GTID Management
Galera Cluster and MariaDB Replication use different GTID formats and implementations, requiring careful configuration to avoid conflicts.
Replication Lag
The external replica experiences the usual latencies of asynchronous replication, causing it to lag behind the real-time state of the cluster.
Failover Complexity
Failover within Galera Cluster is automatic, but failing over to the asynchronous DR replica is manual and requires careful planning.
can be used to replicate between MariaDB Galera Cluster and MariaDB Server. This article will discuss how to do that.
Before we set up replication, we need to ensure that the cluster is configured properly. This involves the following steps:
Set on all nodes in the cluster. See Configuring MariaDB Galera Cluster: Writing Replicated Write Sets to the Binary Log and Using MariaDB Replication with MariaDB Galera Cluster: Configuring a Cluster Node as a Replication Master for more information on why this is important. It is also needed to .
Set to the same value on all nodes in the cluster. See for more information on what this means.
If you want to use replication, then you also need to configure some things to . For example:
needs to be set on all nodes in the cluster.
needs to be set to the same value on all nodes in the cluster so that each cluster node uses the same domain when assigning for Galera Cluster's write sets.
needs to be enabled on all nodes in the cluster. See about that.
needs to be set to the same path on all nodes in the cluster. See
And as an extra safety measure:
should be set to a different value on all nodes in a given cluster, and each of these values should be different than the configured value. This is to prevent a node from using the same domain used for Galera Cluster's write sets when assigning for non-Galera transactions, such as DDL executed with set or DML executed with set.
Before we set up replication, we also need to ensure that the MariaDB Server replica is configured properly. This involves the following steps:
Set to a different value than the one that the cluster nodes are using.
Set to a value that is different than the and values that the cluster nodes are using.
Set and if you want the replica to log the transactions that it replicates.
Our process to set up replication is going to be similar to the process described at , but it will be modified a bit to work in this context.
The very first step is to start the nodes in the first cluster. The first node will have to be . The other nodes can be started normally.
Once the nodes are started, you need to pick a specific node that will act as the replication primary for the MariaDB Server.
Now that the backup has been restored to the MariaDB Server replica, you can start the MariaDB Server process.
You can also set up between the cluster and MariaDB Server, which means that the MariaDB Server replicates from the cluster, and the cluster also replicates from the MariaDB Server.
This page is licensed: CC BY-SA / Gnu FDL
At this point, you need to get the replication coordinates of the primary from the original backup.
The coordinates will be in the file.
mariadb-backup dumps replication coordinates in two forms: and file and position coordinates, like the ones you would normally see from output. In this case, it is probably better to use the coordinates.
For example:
Regardless of the coordinates you use, you will have to set up the primary connection using and then start the replication threads with .
If you want to use GTIDs, then you will have to first set to the coordinates that we pulled from the file, and we would set MASTER_USE_GTID=slave_pos in the command. For example:
If you want to use the file and position coordinates, then you would set MASTER_LOG_FILE and MASTER_LOG_POS in the command to the file and position coordinates that we pulled from the file. For example:
How this is done would depend on whether you want to use the coordinates or the file and position coordinates.
Regardless, you need to ensure that the second cluster is not accepting any writes other than those that it replicates from the cluster at this stage.
To get the GTID coordinates on the MariaDB server, you can check by executing:
Then on the node acting as a replica in the cluster, you can set up replication by setting to the GTID that was returned and then executing :
To get the file and position coordinates on the MariaDB server, you can execute :
Then on the node acting as a replica in the cluster, you would set master_log_file and master_log_pos in the command. For example:
$ rsync -avrP /var/mariadb/backup dc2-dbserver1:/var/mariadb/backup$ mariadb-backup --copy-back \
--target-dir=/var/mariadb/backup/$ chown -R mysql:mysql /var/lib/mysql/mariadb-bin.000096 568 0-1-2SHOW SLAVE STATUS\GSHOW GLOBAL VARIABLES LIKE 'gtid_current_pos';SET GLOBAL gtid_slave_pos = "0-1-2";
CHANGE MASTER TO
MASTER_HOST="c2dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_USE_GTID=slave_pos;
START SLAVE;SHOW SLAVE STATUS\G$ mariadb-backup --backup \
--target-dir=/var/mariadb/backup/ \
--user=mariadb-backup --password=mypassword$ mariadb-backup --prepare \
--target-dir=/var/mariadb/backup/CREATE USER 'repl'@'dc2-dbserver1' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'dc2-dbserver1';CREATE USER 'repl'@'c1dbserver1' IDENTIFIED BY 'password';
GRANT REPLICATION SLAVE ON *.* TO 'repl'@'c1dbserver1';SET GLOBAL gtid_slave_pos = "0-1-2";
CHANGE MASTER TO
MASTER_HOST="c1dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_USE_GTID=slave_pos;
START SLAVE;CHANGE MASTER TO
MASTER_HOST="c1dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_LOG_FILE='mariadb-bin.000096',
MASTER_LOG_POS=568,
START SLAVE;SHOW MASTER STATUSCHANGE MASTER TO
MASTER_HOST="c2dbserver1",
MASTER_PORT=3310,
MASTER_USER="repl",
MASTER_PASSWORD="password",
MASTER_LOG_FILE='mariadb-bin.000096',
MASTER_LOG_POS=568;
START SLAVE;