Disaster Recovery on AWS > Labs > Beginner Level > Amazon ElastiCache for Redis - Global Datastore

Amazon ElastiCache for Redis - Global Datastore

Objective

This exercise will show you the steps for using the Global Datastore mechanism for Amazon ElastiCache instances. If you want more information click here.

By the end of this exercise, you will be able to:

Create Amazon ElastiCache for Redis
Replicate Cluster to Secondary Region
Test Amazon ElastiCache across regions
Promote Secondary Region to Primary

Estimated Duration: 40 minutes

Approximate Cost: 10 USD

Execution

AWS Cloud9

Go to AWS Cloud9

Create AWS Cloud9 environment in Primary Region N. Virginia

For more instructions click here.

Install Redis CLI using Cloud9 Terminal

In order to execute Redis commands, install Redis CLI in your Cloud9 environment.

 # Install command-line JSON processor
 sudo yum install jq -y
 # Install dependencies
 sudo amazon-linux-extras install epel -y
 sudo yum install gcc jemalloc-devel openssl-devel tcl tcl-devel -y
 # Download the redis source code
 sudo wget http://download.redis.io/redis-stable.tar.gz
 sudo tar xvzf redis-stable.tar.gz
 cd redis-stable
 # Build Redis components
 sudo make BUILD_TLS=yes

Repeat steps 1 and 2 using the Secondary Region N. California

You’ll need the two AWS Cloud9 environments in order to access ElastiCache nodes from different regions.

Create an Amazon ElastiCache for Redis cluster

Using AWS Cloud9 terminal in N. Virginia, create a new Redis Cluster (cluster-primary) in the Primary Region.

aws elasticache create-replication-group \
 --replication-group-id cluster-primary \
 --replication-group-description "DR Workshop Labs" \
 --engine redis \
 --multi-az-enabled \
 --cache-node-type cache.r6g.large \
 --num-cache-clusters 2 \
 --region us-east-1

Please wait about 5 minutes to cluster be available.

Check the cluster status

aws elasticache describe-replication-groups \
 --replication-group-id cluster-primary \
 --region us-east-1 |\
 jq -r .ReplicationGroups[0].Status

Copy environment variables

# Export variables
export PRIMARY_ENDPOINT=$(aws elasticache describe-replication-groups --replication-group-id cluster-primary | jq -r '.ReplicationGroups[0].NodeGroups[0].PrimaryEndpoint.Address')
export PORT_NUMBER=$(aws elasticache describe-replication-groups --replication-group-id cluster-primary | jq -r '.ReplicationGroups[0].NodeGroups[0].PrimaryEndpoint.Port')
# Show variables values
echo $PRIMARY_ENDPOINT $PORT_NUMBER

Store keys on ElastiCache Cluster

Connect to Cluster

src/redis-cli -h $PRIMARY_ENDPOINT -p $PORT_NUMBER

Test the connection
```
 PING
```

Write key-value pairs

With the connection opened perform the REDIS command below:

 SET counter 100

 INCR counter

 INCRBY counter 10

 SET userid 5000

 KEYS *

 GET counter

 GET userid

 QUIT

Create a Global Datastore from Regional Cluster

Create a Global Datastore using the primary replication group.

aws elasticache create-global-replication-group \
 --global-replication-group-id-suffix multi-region \
 --primary-replication-group-id cluster-primary \
 --region us-east-1

Please wait about 5 minutes to cluster be available.

Create new cluster in the Secondary Region N. California and add to Global Datastore

 aws elasticache create-replication-group \
 --replication-group-id cluster-secondary \
 --replication-group-description "DR Workshop Labs" \
 --global-replication-group-id ldgnf-multi-region \
 --multi-az-enabled \
 --num-cache-clusters 2 \
 --region us-west-1

Each suffix identifies one region. The suffix “ldgnf” identifies the region N. Virginia and guarantees uniqueness of the global datastore name across multiple regions. See documentation for more details.

Check if both clusters are with Status “associated”

 aws elasticache describe-global-replication-groups \
  --global-replication-group-id ldgnf-multi-region \
  --show-member-info --region us-east-1 |\
  jq -r .GlobalReplicationGroups[0].Members

Please wait about 10-15 minutes to new cluster be associated to Global Datastore.

Test the Secondary Region cluster

Using the AWS Cloud9 in the secondary region N. California

# Export variables
export PRIMARY_ENDPOINT=$(aws elasticache describe-replication-groups --replication-group-id cluster-secondary --region us-west-1 | jq -r '.ReplicationGroups[0].NodeGroups[0].PrimaryEndpoint.Address')
export PORT_NUMBER=$(aws elasticache describe-replication-groups --replication-group-id cluster-secondary --region us-west-1 | jq -r '.ReplicationGroups[0].NodeGroups[0].PrimaryEndpoint.Port')
# Show variables values
echo $PRIMARY_ENDPOINT $PORT_NUMBER

Connect to Secondary Cluster

src/redis-cli -h $PRIMARY_ENDPOINT -p $PORT_NUMBER

Write key-value pairs

With the connection opened perform the REDIS command below:
```
 KEYS *
```
```
 GET counter
```
```
 GET userid
```
Try to create a new key-value pair
```
 SET new-key somevalue
```
The message: "(error) READONLY You can’t write against a read only replica” will be shown, because it’s not permitted to execute write operation on READONLY instances. This instance ROLE is SLAVE mode.

You can check the instance operation mode by ROLE attribute using the command below:
```
 INFO replication
```

Promote Secondary Cluster to Primary

Promote the cluster-secondary in N. California to primary role in the Global Datastore. Using the Cloud9 Terminal execute the command below:
```
aws elasticache failover-global-replication-group \
 --global-replication-group-id ldgnf-multi-region \
 --primary-region us-west-1 \
 --primary-replication-group-id cluster-secondary \
--region us-east-1
```
The failover operation on Global Datastore has an estimated RTO of less than 1 minute.
Using AWS Cloud9 Terminal in N. California connect to Redis again:
```
src/redis-cli -h $PRIMARY_ENDPOINT -p $PORT_NUMBER
```
Now, try to create a new key-value pair again:
```
 SET new-key somevalue
```
Now the write operations could be performed on cluster-secondary in N. California. The same command failover-global-replication-group could be used for failback operation*.

Cleaning up

Remove the cluster-primary from Global Datastore. After the failover command on last step, its Role is Secondary in this point.

 aws elasticache disassociate-global-replication-group \
  --global-replication-group-id ldgnf-multi-region \
  --replication-group-id cluster-primary \
  --replication-group-region us-east-1 \
  --region us-east-1

Wait until the cluster be disassociated.

Delete cluster-primary.

 aws elasticache delete-replication-group \
  --replication-group-id cluster-primary \
  --no-retain-primary-cluster \
  --region us-east-1

Delete Global Datastore.

 aws elasticache delete-global-replication-group \
  --global-replication-group-id ldgnf-multi-region \
  --retain-primary-replication-group \
  --region us-east-1

Check Global DataStore status.

 aws elasticache describe-global-replication-groups \
  --show-member-info \
  --region us-east-1

Delete cluster-secondary.

 aws elasticache delete-replication-group \
  --replication-group-id cluster-secondary \
  --no-retain-primary-cluster \
  --region us-west-1

Conclusion

With this exercise, it was possible to verify how use Global Datastore to replicate data of Amazon ElastiCache for Redis across regions. Global Datastore instances can be used in a strategy of the type Warm Standby, in order to implement disaster recovery capabilities improving the availability.

References: