xCluster (2+ regions)
By default, YugabyteDB provides synchronous replication and strong consistency across geo-distributed data centers. However, many use cases do not require synchronous replication or justify the additional complexity and operation costs associated with managing three or more data centers. A cross-cluster (xCluster) deployment provides asynchronous replication across two data centers or cloud regions.
This exercise simulates a geo-distributed two-data-center (2DC) deployment using two local YugabyteDB clusters, one representing "Data Center - East" and another representing "Data Center - West".
For more information, see the following:
Create two data centers
Create the two data centers as follows:
-
Create and start the local cluster that simulates "Data Center - East" by running the following command from your YugabyteDB home directory:
./bin/yugabyted start \ --advertise_address=127.0.0.1 \ --base_dir=/tmp/ybd1
This starts a single-node local cluster using the IP address of
127.0.0.1
and creates/tmp/ybd1
as the base directory. -
If you are running on macOS and haven't created any loopback addresses, configure one as follows:
sudo ifconfig lo0 alias 127.0.0.2
-
Create and start the second local cluster that simulates "Data Center - West" by running the following command:
./bin/yugabyted start \ --advertise_address=127.0.0.2 \ --base_dir=/tmp/ybd2
This starts a single-node cluster using IP address of
127.0.0.2
and creates/tmp/ybd2
as the base directory.
Create tables
In the default yugabyte
database, you can create the table users
on the "Data Center - East" cluster:
-
Open
ysqlsh
by specifying the host IP address of127.0.0.1
, as follows:./bin/ysqlsh -h 127.0.0.1
-
Create the table
users
, as follows:CREATE TABLE users ( email varchar PRIMARY KEY, username varchar );
Create an identical table on your second cluster:
-
Open
ysqlsh
for "Data Center - West" by specifying the host IP address of127.0.0.2
, as follows:./bin/ysqlsh -h 127.0.0.2
-
Create the table
users
, as followsCREATE TABLE users ( email varchar(35) PRIMARY KEY, username varchar(20) );
Having two identical tables on your clusters allows you to set up xCluster replication across two data centers.
Configure unidirectional replication
To configure "Data Center - West" to be the target of data changes from the "Data Center - East" cluster, you need to use the yb-admin utility setup_universe_replication command. The syntax is as follows:
yb-admin -master_addresses <target-master-addresses> \
setup_universe_replication <source-universe_uuid> \
<source_master_addresses> <source-table-ids>
- target-master-addresses: a comma-separated list of the target YB-Master servers. For this simulation, you have one YB-Master server for the target, 127.0.0.2:7100.
- source-universe-uuid: a unique identifier for the source cluster. Look up the UUID in the source YB-Master UI (http://127.0.0.1:7000).
- source-master-addresses: a comma-separated list of the source YB-Master servers. For this simulation, you have one YB-Master server for the source, 127.0.0.1:7100.
- source-table-ids: A comma-separated list of table UUIDs. For this simulation, the
users
table; look up the UUID in the YB-Master UI (http://127.0.0.1:7000/tables).
Based on actual values you obtained from the YB-Master UI, run the yb-admin setup_universe_replication
command from your YugabyteDB home directory similar to the one shown in the following example:
./bin/yb-admin -master_addresses 127.0.0.2:7100 \
setup_universe_replication 7acd6399-657d-42dc-a90a-646869898c2d \
127.0.0.1:7100 000033e8000030008000000000004000
- target-master-addresses:
127.0.0.2:7100
- source-universe-uuid:
7acd6399-657d-42dc-a90a-646869898c2d
- source-master-addresses:
127.0.0.1:7100
- source-table-ids:
000033e8000030008000000000004000
You should see the following message:
Replication setup successfully
Verify unidirectional replication
To check replication, you can add data to the users
table on one cluster and see that data appear in the users
table on your second cluster.
-
Use the following commands to add data to the "Data Center - East" cluster, making sure you are pointing to the new source host:
./bin/ysqlsh -h 127.0.0.1
INSERT INTO users(email, username) VALUES ('hector@example.com', 'hector'), ('steve@example.com', 'steve');
-
On the target "Data Center - West" cluster, run the following commands to see that data has been replicated between clusters:
./bin/ysqlsh -h 127.0.0.2
SELECT * FROM users;
Expect the following output:
email | username ---------------------+---------- hector@example.com | hector steve@example.com | steve (2 rows)
Configure bidirectional replication
Bidirectional xCluster replication lets you insert data into the same table on either of the clusters and have the data changes added to the other cluster.
To configure bidirectional replication for the same table, you run the yb-admin
setup_universe_replication
command to make the "Data Center - East" cluster the target of the "Data Center - West" cluster. This time, the target is 127.0.0.1:7100, and the source is 127.0.0.2:7100.
Look up the source UUID in the source YB-Master UI (http://127.0.0.2:7000), and source table UUID at http://127.0.0.2:7000/tables.
Based on actual values you obtained from the YB-Master UI, run the yb-admin setup_universe_replication
command similar to the one shown in the following example:
./bin/yb-admin -master_addresses 127.0.0.1:7100 \
setup_universe_replication 0a315687-e9bd-430f-b6f4-ac831193a394 \
127.0.0.2:7100 000030a9000030008000000000004000
- target-master-addresses:
127.0.0.1:7100
- source-universe-uuid:
0a315687-e9bd-430f-b6f4-ac831193a394
- source-master-addresses:
127.0.0.2:7100
- source-table-ids:
000030a9000030008000000000004000
You should see the following message:
Replication setup successfully
Verify bidirectional replication
When the bidirectional replication has been configured, you can add data to the users
table on the "Data Center - West" cluster and see the data appear in the users
table on "Data Center - East" cluster.
-
Use the following commands to add data to the "Data Center - West" cluster, making sure you are pointing to the new source host:
./bin/ysqlsh -h 127.0.0.2
INSERT INTO users(email, username) VALUES ('neha@example.com', 'neha'), ('mikhail@example.com', 'mikhail');
-
On the new target cluster, run the following commands to see that data has been replicated between clusters:
./bin/ysqlsh -h 127.0.0.1
SELECT * FROM users;
You should see the following output:
email | username ---------------------+---------- hector@example.com | hector steve@example.com | steve neha@example.com | neha mikhail@example.com | mikhail (4 rows)
Add tables
You can add more tables to an existing replication using the yb-admin command alter_universe_replication
add_table
:
yb-admin -master_addresses <target-master-addresses> \
alter_universe_replication <source-universe_uuid> \
add_table <source-table-ids>
The following is an example command:
./bin/yb-admin -master_addresses 127.0.0.2:7100 \
alter_universe_replication 7acd6399-657d-42dc-a90a-646869898c2d \
add_table 000030a9000030008000000000004000
For details, see alter_universe_replication.
Clean up
You can shut down the local cluster by following the instructions provided in Destroy a local cluster.