Supertubes

Kafka disaster recovery on Kubernetes using MirrorMaker2

Supertubes offers multiple disaster recovery methods for Apache Kafka.

This section describes how to configure MirrorMaker2 with Supertubes to back up a Kafka cluster to a remote Kafka cluster running on a separate Kubernetes cluster, and how to recover the lost Kafka cluster. This disaster recovery solution uses a MirrorMaker2 active/active, active/passive topology setup.

Note: Supertubes and MirrorMaker2 supports other scenarios as well, such as fan-out, aggregation, or cluster migration. If you want to use Supertubes in one of these scenarios, contact us for details.

How it works 🔗︎

MirrorMaker2 uses the Connect framework to replicate topics between Kafka clusters.

Both topics and consumer groups are replicated
Topic configuration and ACLs are replicated
Cross-cluster offsets are synchronized
Partitioning is preserved

Supertubes is using MirrorMaker2 to set up cross-cluster replication between remote Kafka clusters and recover a lost Kafka cluster from a remote Kafka cluster. It deploys a MirrorMaker2 instance for each Kafka cluster into the same namespace where the Kafka cluster resides. The MirrorMaker2 instance acts as a:

Producer targeting the Kafka cluster running on the same Kubernetes cluster and namespace (it is recommended to have MirrorMaker2 deployed close to the target Kafka cluster)
Consumer for the remote Kafka clusters

Cross-cluster replication

Prepare the MirrorMaker2 descriptor 🔗︎

Supertubes expects a descriptor file in yaml or json format that describes the topology of the Kafka clusters and the MirrorMaker2 replication topology in the following format.

# list of Kubernetes config file paths of clusters hosting our Kafka clusters that we want to make MM2 deployments aware of
kubernetesConfigs:
- # path-to-the-kubeconfig
- # path-to-the-kubeconfig
…
# list of Kafka clusters to make MM2 deployments aware of
kafkaClusters:
- namespace: # kubernetes namespace hosting the Kafka cluster, defaults to 'kafka'
  name: # Kafka cluster name, defaults to 'kafka'
  kubernetesConfigContext: # name of Kubernetes configuration context as defined in the kubeconfig files which references the Kubernetes cluster hosting the Kafka cluster. If not specified, the default context is used.
  alias: # kafka cluster alias by which MM2 refers to this Kafka cluster as (e.g. kafka1). If not provided it defaults to '${kubernetesConfigContext}_${namespace}_${name}'
  internalListenerName: # name of the internal listener which local MM2 instances access this Kafka cluster through
  externalListenerName: # name of the external listener which remote MM2 instances access this Kafka cluster through
mirrorMaker2Spec:
  kafkaHeapOpts: # heap opts setting for MirrorMaker2, defaults to -Xms256M -Xmx2G
  resources:
  nodeSelector:
  tolerations:
  affinity:

mirrorMaker2Properties: |
  # replication topologies and flows, mm2 config, etc.

  # two way replication between 3 Kafka clusters
  kafka1->kafka2.enabled=true
  kafka1->kafka3.enabled=true

  kafka2->kafka1.enabled=true
  kafka2->kafka3.enabled=true

  kafka3->kafka1.enabled=true
  kafka3->kafka2.enabled=true

Supertubes automatically generates the MirrorMaker2 configuration for each MirrorMaker2 instance (MirrorMaker2 has its proprietary configuration format). Supertubes maintains the Kafka servers section of the file, while the replication flows and other MirrorMaker2 settings are populated from the mirrorMaker2Properties provided by the user. The generated MirrorMaker2 configuration file looks like:

# maintained by supertubes
clusters: kafka1, kafka2, kafka3, ...

kafka1.bootstrap.servers=... # internal kafka bootstrap servers URL if MM2 is on the same Kubernetes cluster as Kafka cluster, otherwise external kafka bootstrap servers URL
kafka2.bootstrap.servers=... # internal kafka bootstrap servers URL if MM2 is on the same Kubernetes cluster as Kafka cluster, otherwise external kafka bootstrap servers URL
kafka3.bootstrap.servers=... # internal kafka bootstrap servers URL if MM2 is on the same Kubernetes cluster as Kafka cluster, otherwise external kafka bootstrap servers URL

# user provided mm2 settings
kafka1->kafka2.enabled=true
kafka1->kafka3.enabled=true

kafka2->kafka1.enabled=true
kafka2->kafka3.enabled=true

kafka3->kafka1.enabled=true
kafka3->kafka2.enabled=true

Note: Keep the replication flow settings the same across all MirrorMaker2 instances to avoid omitting topics from cross-cluster replication.

In the example above, MirrorMaker2 will replicate topics from kafka1 to kafka2 and the other way around:

topics from kafka1 are replicated to kafka2 as kafka1.{topic-name}, similarly
topics from kafka2 are replicated to kafka1 as kafka2.{topic-name}.

As an example, if we have a topic named topic1 on both Kafka clusters, then:

kafka1 will have topic1 and kafka2.topic1, and
kafka2 will have topic1 and kafka2.topic1, respectively.

Bidirectional cross-cluster replication happens similarly between kafka2 <-> kafka3 and kafka1 <-> kafka3.

supertubes mm2 deploy -f <path-to-mm2-deployment-descriptor>

Configure Supertubes and MirrorMaker2 🔗︎

Create two Kubernetes clusters, for example, named as example-k8s-cluster-1 and example-k8s-cluster-2.
Install Supertubes on both Kubernetes clusters.
1. Provide a common root certificate for the Istio deployments. To ensure that the Kafka clusters are accessed through TLS, Supertubes automatically sets up an Istio service mesh, and runs Kafka inside the mesh on each Kubernetes cluster. That way, Istio handles TLS at the networking layer.
```
supertubes install --root-cert=root-cert.pem --ca-cert=ca-cert.pem --ca-key=ca-key.pem -a --no-demo-cluster -c {example-k8s-cluster-1-kubeconfig.yaml}
```
  If you don’t have root and intermediate CA certificates at hand, you can use this tool to generate self-signed certificates quickly.
2. Repeat the previous step for the other cluster.

Create Kafka clusters on both Kubernetes clusters

supertubes cluster create --namespace kafka -c {example-k8s-cluster-1-kubeconfig.yaml} -f https://raw.githubusercontent.com/banzaicloud/koperator/master/config/samples/kafkacluster-with-istio.yaml

supertubes cluster create --namespace kafka -c {example-k8s-cluster-2-kubeconfig.yaml} -f https://raw.githubusercontent.com/banzaicloud/koperator/master/config/samples/kafkacluster-with-istio.yaml

Wait until the Kafka clusters becomes operational:

supertubes cluster get --namespace kafka --kafka-cluster kafka -c {example-k8s-cluster-1-kubeconfig.yaml}
Namespace  Name   State           Image                         Alerts  Cruise Control Topic Status  Rolling Upgrade Errors  Rolling Upgrade Last Success
kafka      kafka  ClusterRunning  banzaicloud/kafka:2.13-2.4.0  0       CruiseControlTopicReady      0                       2020-03-04 14:07:36

Enable cross-cluster replication with MirrorMaker2. In the MirrorMaker2 descriptor file, you have to reference the Kafka clusters. For example, the one running on example-k8s-cluster-1 as kafka1 and the one running on example-k8s-cluster-2 as kafka2.

supertubes mm2 deploy -f -<<EOF
# list of Kubernetes config file paths of clusters hosting our Kafka clusters that we want to make MM2 deployments aware of
kubernetesConfigs:
  - {example-k8s-cluster-1-kubeconfig.yaml}
  - {example-k8s-cluster-2-kubeconfig.yaml}

# list of Kafka clusters to make MM2 deployments aware of
kafkaClusters:
  - namespace: kafka
    name: kafka
    kubernetesConfigContext: kubernetes-admin@example-k8s-cluster-1  # the context from {example-k8s-cluster-1-kubeconfig.yaml}
    alias: kafka1 # name MM2 refers to this Kafka cluster to
    internalListenerName: internal # name of the Kafka cluster internal listener local MM2 instance to use
    externalListenerName: external # name of the Kafka cluster external listener remote MM2 instances to use
  - namespace: kafka
    name: kafka
    kubernetesConfigContext: kubernetes-admin@example-k8s-cluster-2 # the context from {example-k8s-cluster-2-kubeconfig.yaml}
    alias: kafka2 # name MM2 refers to this Kafka cluster to
    internalListenerName: internal # name of the Kafka cluster internal listener local MM2 instance to use
    externalListenerName: external # name of the Kafka cluster external listener remote MM2 instances to use

mirrorMaker2Properties: |-
  # replication topologies and flows, mm2 config, etc.
  kafka1->kafka2.enabled=true
  kafka2->kafka1.enabled=true

    # we don't have ACLs set so skip replicating them
  sync.topic.acls.enabled=false
EOF

Create some Kafka topics.

Create a topic named testtopic on both Kafka clusters, for example:

supertubes cluster topic create --namespace kafka --kafka-cluster kafka -c {example-k8s-cluster-1-kubeconfig.yaml} -f -<<EOF
apiVersion: kafka.banzaicloud.io/v1alpha1
kind: KafkaTopic
metadata:
  name: testtopic
spec:
  name: testtopic
  partitions: 3
  replicationFactor: 2
  config:
    "retention.ms": "28800000"
    "cleanup.policy": "delete"
EOF

Repeat the previous step on the other Kafka cluster.

Generate client certificates. The Kafka clusters run inside an Istio service mesh with TLS enabled. This means you need a client certificate to write messages to your topic. To get a client certificate, run:
```
supertubes istio certificate generate-client-certificate -c {example-k8s-cluster-1-kubeconfig.yaml} > cert-data.json
```
The returned JSON contains the following fields in base64-encoded format:
- client-cert.pem: the client certificate
- client-key.pem: the client key
- ca-cert.pem: the CA certificate
- root-cert.pem: the root certificate
- cert-chain.pem: the certificate chain containing root and CA certificate

Find the public addresses through which the Kafka cluster is exposed on both Kubernetes cluster:

kubectl get svc -n kafka kafka-meshgateway
NAME                TYPE           CLUSTER-IP      EXTERNAL-IP                                                                PORT(S)                                                           AGE
kafka-meshgateway   LoadBalancer   10.10.171.247   a7c265ab846c14f8fa082773fee7c0da-2063154997.eu-north-1.elb.amazonaws.com   19090:31645/TCP,19091:32240/TCP,19092:32483/TCP,29092:30681/TCP   61m

kubectl get svc -n kafka kafka-meshgateway
NAME                TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)                                                           AGE
kafka-meshgateway   LoadBalancer   10.10.161.160   51.124.19.105   19090:32651/TCP,19091:31402/TCP,19092:30403/TCP,29092:31586/TCP   57m

Write messages to testtopic on both clusters. Use kafkacat to produce and consume messages from/to our testtopic topic.

kafkacat -b a7c265ab846c14f8fa082773fee7c0da-2063154997.eu-north-1.elb.amazonaws.com:29092 -X security.protocol=SSL -X ssl.ca.location=cert_chain.pem -X ssl.certificate.location=client.pem -X ssl.key.location=client.key -P -t testtopic

kafka1: message 1
kafka1: message 2

kafkacat -b 51.124.19.105:29092 -X security.protocol=SSL -X ssl.ca.location=cert_chain.pem -X ssl.certificate.location=client.pem -X ssl.key.location=client.key -P -t testtopic

kafka2: message 1
kafka2: message 2

Check replicated messages. Verify that MirrorMaker replicated messages from testtopic from kafka1 to kafka2 under kafka2.testtopic topic:

kafkacat -b a7c265ab846c14f8fa082773fee7c0da-2063154997.eu-north-1.elb.amazonaws.com:29092 -X security.protocol=SSL -X ssl.ca.location=cert_chain.pem -X ssl.certificate.location=client.pem -X ssl.key.location=client.key -C -t kafka2.testtopic -c2
kafka2: message 1
kafka2: message 2

kafkacat -b 51.124.19.105:29092 -X security.protocol=SSL -X ssl.ca.location=cert_chain.pem -X ssl.certificate.location=client.pem -X ssl.key.location=client.key -C -t kafka1.testtopic -c2
kafka1: message 2
kafka1: message 1

The summary of what you are seeing is:

+-- kafka1
|   +-- testtopic
|       +-- kafka1: message 1
|       +-- kafka1: message 2
|   +-- kafka2.testtopic
|       +-- kafka2: message 1
|       +-- kafka2: message 2
+-- kafka2
|   +-- testtopic
|       +-- kafka2: message 1
|       +-- kafka2: message 2
|   +-- kafka1.testtopic
|       +-- kafka1: message 1
|       +-- kafka1: message 2

Recover a lost Kafka cluster 🔗︎

In the event of losing one of the Kubernetes clusters that hosts your Kafka cluster, complete the following steps.

While the new cluster is provisioned, direct the client applications (consumers and producers) to the remaining Kafka clusters.
Create a new Kubernetes cluster, for example, example-k8s-cluster-new.
Wait until the new Kubernetes cluster is ready.

Install Supertubes on the new cluster.

supertubes install --root-cert=root-cert.pem --ca-cert=ca-cert.pem --ca-key=ca-key.pem -a --no-demo-cluster -c {example-k8s-cluster-new-kubeconfig.yaml}

Create a new Kafka cluster to replace the lost one. In the following examples and in the MirrorMaker2 descriptor, we will refer to this new Kafka cluster as kafka1-new.

supertubes cluster create --namespace kafka -c {example-k8s-cluster-new-kubeconfig.yaml} -f https://raw.githubusercontent.com/banzaicloud/koperator/master/config/samples/kafkacluster-with-istio.yaml

Wait until the Kafka clusters becomes operational

supertubes cluster get --namespace kafka --kafka-cluster kafka -c {example-k8s-cluster-new-kubeconfig.yaml}
Namespace  Name   State           Image                         Alerts  Cruise Control Topic Status  Rolling Upgrade Errors  Rolling Upgrade Last Success
kafka      kafka  ClusterRunning  banzaicloud/kafka:2.13-2.4.0  0       CruiseControlTopicReady      0                       2020-03-04 16:42:34

Create a topic named testtopic in the new Kafka cluster.

supertubes cluster topic create --namespace kafka --kafka-cluster kafka -c {example-k8s-cluster-new-kubeconfig.yaml} -f -<<EOF
apiVersion: kafka.banzaicloud.io/v1alpha1
kind: KafkaTopic
metadata:
  name: testtopic
spec:
  name: testtopic
  partitions: 3
  replicationFactor: 2
  config:
    "retention.ms": "28800000"
    "cleanup.policy": "delete"
EOF

Create a new alias for the new Kafka cluster. The new (replacement) Kafka cluster must get a new alias and should not reuse the alias of the lost Kafka cluster, because MirrorMaker2 doesn’t replicate topics that are prefixed with the name of a cluster alias.

Update the MirrorMaker2 topology descriptor file to reflect the new Kubernetes cluster and Kafka cluster alias (kafka1-new) as well.

supertubes mm2 deploy -f -<<EOF
# list of Kubernetes config file paths of clusters hosting our Kafka clusters that we want to make MM2 deployments aware of
kubernetesConfigs:
  - {example-k8s-cluster-new-kubeconfig.yaml}
  - {example-k8s-cluster-2-kubeconfig.yaml}

# list of Kafka clusters to make MM2 deployments aware of
kafkaClusters:
  - namespace: kafka
    name: kafka
    kubernetesConfigContext: kubernetes-admin@example-k8s-cluster-new
    alias: kafka1-new # name MM2 refers to this Kafka cluster to
    internalListenerName: internal # name of the Kafka cluster internal listener local MM2 instance to use
    externalListenerName: external # name of the Kafka cluster external listener remote MM2 instances to use
  - namespace: kafka
    name: kafka
    kubernetesConfigContext: kubernetes-admin@example-k8s-cluster-2
    alias: kafka2 # name MM2 refers to this Kafka cluster to
    internalListenerName: internal # name of the Kafka cluster internal listener local MM2 instance to use
    externalListenerName: external # name of the Kafka cluster external listener remote MM2 instances to use

mirrorMaker2Properties: |-
  # replication topologies and flows, mm2 config, etc.
  kafka1-new->kafka2.enabled=true
  kafka2->kafka1-new.enabled=true

  sync.topic.acls.enabled=false
EOF

Run the following command with the modified descriptor file:

$ supertubes mm2 deploy -f <path-to-mm2-deployment-descriptor>

Wait until Supertubes updates all MirrorMaker2 instances.
The new Kafka cluster starts catching up from the other clusters.

Verify that all messages from the lost kafka1 cluster are replicated from the backup kafka2 cluster to the newly created kafka1-new replacement Kafka cluster.

kubectl get svc -n kafka kafka-meshgateway
NAME                TYPE           CLUSTER-IP      EXTERNAL-IP                                                               PORT(S)                                                           AGE
kafka-meshgateway   LoadBalancer   10.10.235.122   abee2dfdb54dc485e8449b776a649377-1677360459.eu-west-1.elb.amazonaws.com   19090:30870/TCP,19091:32756/TCP,19092:30961/TCP,29092:31455/TCP   25m

kafkacat -b abee2dfdb54dc485e8449b776a649377-1677360459.eu-west-1.elb.amazonaws.com:29092 -X security.protocol=SSL -X ssl.ca.location=cert_chain.pem -X ssl.certificate.location=client.pem -X ssl.key.location=client.key -P -t testtopic

kafka1-new: message 1
kafka1-new: message 2