Replicating data from CDP PvC Base cluster to Data Hub cluster with SRM deployed in Data Hub cluster

You can set up and configure an instance of SRM running in a Data Hub cluster to replicate data between the Data Hub cluster and a CDP PvC Base cluster. In addition, you can use SMM to monitor the replication process. Review the following example to learn how this can be set up.

Consider the following replication scenario:

In this scenario, data is replicated from a CDP PvC Base cluster to a Data Hub cluster by an SRM instance that is deployed in the Data Hub cluster.

The CDP PvC Base cluster has Kafka deployed on it. It is a secure cluster that has TLS/SSL encryption enabled and uses PLAIN authentication. In addition, it uses Ranger for authorization.

The Data Hub cluster is provisioned with the one of the default Streams Messaging cluster definitions.

This example scenario does not go into detail on how to set up the clusters and assumes the following:

A Data Hub cluster provisioned with the Streams Messaging Light Duty or Heavy Duty cluster definition is available.
For more information, see Creating your first Streams Messaging cluster in the CDF for Data Hub library. Alternatively, you can also review the cloud provider specific cluster creation instructions available in the Cloudera Data Hub library.
A CDP PvC Base cluster with Kafka is available. This cluster has TLS/SSL encryption enabled, uses PLAIN authentication, and has Ranger for authorization. For more information, see the CDP Private Cloud Base Installation Guide.
Network connectivity and DNS resolution are established between the clusters.

Obtain PLAIN credentials for SRM.
The credentials of a PLAIN user that can access the CDP PvC Base cluster are required. These credentials are supplied to SRM in a later step. In this example [***PLAIN USER***] and [***PLAIN USER PASSWORD***] is used to refer to these credentials.
note
Typically, Kerberos cannot be easily configured to span across an on-premise and a public cloud environment. Therefore, these instructions assume that these environments use authentication methods that are easy to interoperate in such hybrid environments like LDAP or PAM authentication. For more information on how you can configure your Kafka service to use LDAP or PAM, see Kafka Authentication.
Add Ranger permissions for the PLAIN user in the CDP PvC cluster:

You must ensure that the PLAIN user you obtained has correct permissions assigned to it in Ranger. Otherwise, SRM will not be able to access Kafka resources on the CDP PvC Base cluster.
1. Access the Cloudera Manager instance of your CDP PvC Base cluster.
2. Go to Ranger > Ranger Admin Web UI.
3. Log in to the Ranger Console (Ranger Admin Web UI).
4. Add the [***PLAIN USER***] to the following policies:
  - All - consumergroup
  - All - topic
  - All - transactionalid
  - All - cluster
  - All - delegationtoken
Acquire the CDP PvC Base cluster truststore and add it to the Data Hub cluster:
The actions you need to take differ depending on how TLS is set up in the CDP PvC Base cluster:
- Auto TLS
- Manual TLS
Obtain the certificate of the Cloudera Manager root Certificate Authority and its password.
The Certificate Authority certificate and its password can be obtained using the Cloudera Manager API. The following steps describe how you can retrieve the certificate and password using the Cloudera Manager API Explorer. Alternatively, you can also retrieve the certificate and password by calling the appropriate endpoints in your browser window or using curl.

Access the Cloudera Manager instance of your CDP PvC Base cluster.

Go to Support > API Explorer.

Find CertManagerResource.

Select the /certs/truststore GET operation and click Try it out.

Enter the truststore type.

Click Execute.

Click Download file under Responses.
The downloaded file is your certificate.

Select the /certs/truststorePassword GET operation and click Try it out.

Click Execute.
The password is displayed under Responses.

Run the following command to create the truststore:
keytool \ -importcert \ -storetype JKS \ -noprompt \ -keystore cdppvc-truststore.jks \ -storepass ***PASSWORD*** \ -alias cdppvc-cm-ca \ -file ***PATH TO CM CA CERTIFICATE***
Note down the password, it is needed in a later step.

Copy the cdpdc-truststore.jks file to a common location on all the hosts in your CDP Data Hub cluster.
Cloudera recommends that you use the following location: /opt/cloudera/security/cdppvc-truststore.jks.

Set the correct file permissions.
Use 751 for the directory and 444 for the truststore file.
Note down the CDP PvC Base cluster's truststore location and password, these should be known to you.

Copy the truststore file to a common location on all the hosts in your CDP Data Hub cluster.
Cloudera recommends that you use the following location: /opt/cloudera/security/truststore.jks.

Set the correct file permissions.
Use 751 for the directory and 444 for the truststore file.
Configure the SRM properties in the Data Hub cluster:
1. Access the Cloudera Manager instance of your Data Hub cluster.
2. Go to Streams Replication Manager > Configuration and configure the following properties:
  - Streams Replication Manager Cluster alias: datahub, cdppvc
  - Streams Replication Manager Driver Target Cluster: datahub, cdppvc
    note
    This property must either contain all aliases or left blank. Leaving the property blank has the same effect as adding all aliases.
  - Streams Replication Manager Service Target Cluster: datahub
  - Streams Replication Manager's Replication Configs:
    important
    Passwords that you set in this property are stored in plaintext.
```
#Bootstrap servers:
cdppvc.bootstrap.servers=[***MY-CDP-PVC-CLUSTER-HOST-1.COM:9093***],[***MY-CDP-PVC-CLUSTER-HOST-2:9093***]
datahub.bootstrap.servers=[***MY-DATAHUB-CLUSTER-HOST-1.COM:9093***],[***MY-DATAHUB-CLUSTER-HOST-2.COM:9093***]

#Replications:
cdppvc->datahub.enabled=true

#Security properties for the CDP PvC Base cluster:
cdppvc.security.protocol=SASL_SSL
cdppvc.sasl.mechanism=PLAIN
cdppvc.sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="[***PLAIN USER***]" password="[***PLAIN USER PASSWORD***]";
cdppvc.ssl.truststore.location=/opt/cloudera/security/cdppvc-truststore.jks
cdppvc.ssl.truststore.password=***PASSWORD***

#Use the FQDN when specifying cluster hosts.
#The terminating semicolon in the [***ALIAS***].sasl.jaas.config property must be included in the configuration.
#The value of the [***ALIAS***].ssl.truststore.location is the location where you copied the truststore in a previous step.
#The [***ALIAS***].ssl.truststore.password property must be specified. Otherwise, the configuration might get overriden by the service ssl.truststore.password property.
```
    note
    This configuration does not specify the security properties required by SRM to connect to the co-located Kafka cluster (the cluster SRM is deployed in). This is because these properties are automatically passed by Cloudera Manager to SRM in the background.
    note
    The configuration of the security properties with the cdppvc. prefix depend on the security configuration of the CDP PvC Base cluster. This specific example is for a cluster that has TLS/SSL encryption and PLAIN authentication enabled. You need to change these configurations based on the setup of your CDP PvC Base cluster.
3. Click Save.
4. Restart SRM.
5. Deploy client configuration for SRM.

Start data replication topics using the srm-control tool:

SSH as an administrator to any of the SRM hosts in the Data Hub cluster.
```
ssh [***USER***]@[***MY-DATAHUB-CLUSTER.COM***]
```

Create a configuration file for the srm-control tool.

The srm-control tool behaves as a Kafka client and requires configuration that is similar to any Kafka client. The configuration file is specified with the --config option when you run the tool. The configuration file must include cluster alias definitions, as well as properties related to connection information and security. Cluster aliases are defined a single time, connection and security properties are defined separately for each alias (cluster). In this example the file is named srm.properties.

#Bootstrap servers:
cdppvc.bootstrap.servers=[***MY-CDP-PVC-CLUSTER-HOST-1.COM:9093***],[***MY-CDP-PVC-CLUSTER-HOST-2:9093***]
datahub.bootstrap.servers=[***MY-DATAHUB-CLUSTER-HOST-1.COM:9093***],[***MY-DATAHUB-CLUSTER-HOST-1.COM:9093***]

#CDP PVC Base cluster’s security properties:
cdppvc.security.protocol=SASL_SSL
cdppvc.sasl.mechanism=PLAIN
cdppvc.sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="[***PLAIN USER***]" password="[***PLAIN USER PASSWORD***]";
cdppvc.ssl.truststore.location=/opt/cloudera/security/cdppvc-truststore.jks
cdppvc.ssl.truststore.password=[***PASSWORD***]

#Data Hub cluster's security properties:
datahub.security.protocol=SASL_SSL
datahub.sasl.mechanism=GSSAPI
datahub.sasl.kerberos.service.name=kafka
datahub.sasl.jaas.config=com.sun.security.auth.module.Krb5LoginModule required useKeyTab=true keyTab="[***PATH TO KEYTAB FILE***]" storeKey=true useTicketCache=false principal="[***MY KERBEROS PRINCIPAL****]";
datahub.ssl.truststore.location=/opt/cloudera/security/datahub-truststore.jks
datahub.ssl.truststore.password=[***PASSWORD***]

#Use the FQDN when specifying the cluster hosts.
#The terminating semicolon in the [***ALIAS***].sasl.jaas.config properties must be included in the configuration.
#The value of the cdpdc.ssl.truststore.location property is the location where you copied the truststore in a previous step.

Use the srm-control tool with the topics subcommand to add topics to the allow list:

srm-control --config ./srm.properties topics --source cdppvc --target datahub --add [***TOPIC NAME***]

Use the srm-control tool with the groups subcommand to groups to the allow list:

srm-control --config ./srm.properties groups --source cdppvc --target datahub --add ".*"

Monitor the replication process.
Access the SMM UI in the Data Hub cluster and go to the Cluster Replications page. The replications you set up will be visible on this page.
note
If the topics or groups you added for replication are newly created, they might not be immediately visible. This is due to how frequently SRM checks for newly created topics and consumer groups. By default, this is set to 10 minutes, but can be configured with the Refresh Topics Interval Seconds and Refresh Groups Interval Seconds SRM properties. If at first your topics do not appear, wait a few minutes and refresh the page.