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Dual region

Camunda 8 is compatible with a dual-region setup under certain limitations. This allows Camunda 8 to run in a mix of active-active and active-passive setups, resulting in an overall active-passive setup. The following will explore the concept, limitations, and considerations.

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You should get familiar with the topic, the limitations of the dual-region setup, and the general considerations on operating a dual-region setup.

Active-active and active-passive​

Active-active and active-passive are standard setups used in dual region configurations to ensure that applications remain available and operational in case of failures.

In an active-active setup, multiple application instances run simultaneously in different regions, actively handling user requests. This allows for better load balancing and fault tolerance, as traffic can spread across regions. If one region fails, the workload can shift to another without causing disruptions.

By contrast, an active-passive setup designates one region as the main or active region where all user requests are processed. The other region remains on standby until needed, only becoming active if the previously active region fails. This setup is easier to manage but may result in higher delays during failover events.

Disclaimer​

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  • Customers must develop and test operational procedures in non-production environments based on the framework steps outlined by Camunda before applying them in production setups.
  • Before advancing to production go-live, validating these procedures with Camunda is strongly recommended.
  • Customers are solely responsible for detecting any regional failures and implementing the necessary operational procedures.

Architecture​

The illustrated architecture consists of two regions. Each region houses a Kubernetes cluster in which Camunda 8 is deployed. Those two Kubernetes clusters are capable of communicating with each other.

One of the regions will be considered active and the other passive. User traffic must only reach the active region. We consider Region 0 (underlined in green) the active region and Region 1 the passive region. In this case, user traffic would only go to Region 0. Region 1 would be considered passive and used in case of the loss of the active region. Due to Zeebe's data replication, you can recover from an active region loss by utilizing the passive region without much downtime.

Zeebe stretches across the regions due to its use of the Raft protocol, allowing it to communicate and replicate data between all brokers. Zeebe exports data to two Elasticsearch instances, one in each region. Operate and Tasklist will import the previously exported data and run per region.

The currently supported Camunda 8 Self-Managed components are:

  • Zeebe (workflow engine)
  • Elasticsearch (database)
  • Operate
  • Tasklist

User traffic​

The overall system is active-passive, even though some components may be active-active. You will have to take care of the user traffic routing or DNS by yourself, and won't be considered further. Select one region as the actively serving region and route the user traffic there. In case of a total region failure, route the traffic to the passive region yourself.

Components​

Zeebe​

Zeebe, as a workflow engine, is fully active-active and replicates data between its brokers. Due to its replication logic, it can handle an entire region failure without data loss, but requires a proper partition and replication setup. Consider reading through the cluster technical concept to learn more about the Raft protocol.

Elasticsearch​

We treat Elasticsearch as an active-passive component. While it may be possible to deploy it in active-active mode and stretch across regions, it's not officially documented by Elasticsearch. Such a setup generally brings its own challenges we can't control and may negatively impact the performance of Zeebe.

We recommend the approach of one Elasticsearch per region and configuring Zeebe to export the Elasticsearch data in both regions.

Components​

Camunda components are active-passive components and in their current state not highly available as we're limited by the included exporters that would cause data issues when running multiple instances at the same time.

In every region, there can be only a single component instance running (for example in Region 0, 1 instance of Operate, 1 instance of Tasklist; same in Region 1).

This means that one instance will be actively serving traffic, while the other is on standby.

Operate​

In the event of a total active region loss, the following data will be lost:

  • Uncompleted batch operations
Tasklist​

In the event of a total active region loss, the following data will be lost:

  • Assignments of uncompleted tasks

Requirements​

  • Camunda 8
    • Minimum Helm chart version 9.3+
    • Minimum component images
      • Elasticsearch 8.9+
        • OpenSearch (both managed and self-managed) is not supported
      • Operate 8.5+
      • Tasklist 8.5+
      • Zeebe 8.5+
      • Zeebe Gateway 8.5+
  • Two Kubernetes clusters
    • OpenShift is not supported
    • The Kubernetes clusters need to be able to connect to each other (for example, via VPC peering)
    • Maximum round trip time (RTT) of 100ms between the two Kubernetes clusters
  • Open ports between the two Kubernetes clusters
    • 9200 for Elasticsearch for Zeebe to push data cross-region
    • 26500 for communication to the Zeebe Gateway from client/workers
    • 26501 for the Zeebe brokers and Zeebe Gateway communication
    • 26502 for the Zeebe brokers and Zeebe Gateway communication
  • Only specific combinations of Zeebe broker counts and replication factors are supported
    • clusterSize must be a multiple of 2 and a minimum of 4 to evenly distribute the brokers across the two regions.
    • replicationFactor must be 4 to ensure that the partitions are evenly distributed across the two regions.
    • partitionCount is not restricted and depends on your workload requirements, consider having a look at understanding sizing and scalability behavior.
      • For further information and visualization of the partition distribution, consider consulting the documentation on partitions.
  • The customers operating their Camunda 8 setup are responsible for detecting a regional failure and executing the operational procedure.

Limitations​

  • Camunda 8 must be installed with the Camunda Helm chart.
    • Alternative installation methods (with docker-compose installation, for example) are not supported.
  • Looking at the whole Camunda platform, it's active-passive, while some key components are active-active.
    • There's always one active and one passive region for serving active user traffic.
    • Serving traffic to both regions will result in a detachment of the components and users potentially observing different data in Operate and Tasklist.
  • Identity is not supported.
    • Multi-tenancy does not work.
    • Role Based Access Control (RBAC) does not work.
  • Optimize is not supported.
    • This is due to Optimize depending on Identity to work.
  • Connectors are not supported.
    • This is due to Connectors depending on Operate to work for inbound Connectors and potentially resulting in race condition.
  • During the failback procedure, there’s a small chance that some data will be lost in Elasticsearch affecting Operate and Tasklist.
    • This does not affect the processing of process instances in any way. The impact is that some information about the affected instances might not be visible in Operate and Tasklist.
    • This is further explained in the operational procedure during the relevant step.
  • Zeebe cluster scaling is not supported.
  • Web-Modeler is a standalone component and is not covered in this guide.
    • Modeling applications can operate independently outside of the automation clusters.
  • Kubernetes service meshes are currently unsupported, and we advise against their use for the setup.

Considerations​

Multi-region setups in itself bring their own complexity. The following items are such complexities and are not considered in our guides. You should familiarize yourself with those before deciding to go for a dual-region setup.

  • Managing multiple Kubernetes clusters and their deployments across regions
  • Monitoring and alerting
  • Increased costs of multiple clusters and cross-region traffic
  • Data consistency and synchronization challenges (for example, brought in by the increased latency)
    • Bursts of increased latency can already have an impact
  • Managing DNS and incoming traffic

Region loss​

In a dual-region setup, a loss of a region will invariably affect Camunda 8, regardless of whether it's the active or passive region.

This means the Zeebe stretch cluster will not have a quorum when half of its brokers are not reachable anymore and will stop processing any new data. This will also affect the components, as they cannot update or push new workflows. Essentially, this means the workflow engine will halt until the region failover procedure is complete.

The operational procedure looks in detail at short-term recovery from a region loss and how to long-term fully re-establish the lost region. The procedure works the same way for active or passive region loss since we don't consider traffic routing (DNS) in the scenario.

Active region loss​

The loss of the active region means:

  • The loss of previously mentioned data in Operate and Tasklist.
  • Traffic is routed to the active region, which now can't be served anymore.
  • The workflow engine will stop processing due to the loss of the quorum.

The following high-level steps need to be taken in case of the active region loss:

  1. Follow the operational procedure to temporarily recover from the region loss and unblock the workflow engine.
  2. Reroute traffic to the passive region that will now become the new active region.
  3. Due to the loss of data in Operate and Tasklist, you'll have to:
    1. Reassign uncompleted tasks in Tasklist.
    2. Recreate batch operations in Operate.
  4. Follow the operational procedure to recreate a new permanent region that will become your new passive region.

Passive region loss​

The loss of the passive region means the workflow engine will stop processing due to the loss of the quorum.

The following high-level steps need to be taken in case of passive region loss:

  • Follow the operational procedure to temporarily recover from the region loss and unblock the workflow engine.
  • Follow the operational procedure to recreate a new permanent region that will become your new passive region.

Unlike the active region loss, no data will be lost, nor will any traffic require rerouting.

Disaster Recovery​

Based on all the limitations and requirements, you can consider the Recovery Point Objective (RPO) and Recovery Time Objective (RTO) in case of a disaster recovery to help with the risk assessment.

The Recovery Point Objective (RPO) is the maximum tolerable data loss measured in time.

The Recovery Time Objective (RTO) is the time to restore services to a functional state.

For Zeebe the RPO is 0.

For Operate and Tasklist the RPO is close to 0 for critical data due to the previously mentioned small chance of data loss in Elasticsearch during the failback procedure.

The RTO can be considered for the failover and failback procedures, both resulting in a functional state.

  • failover has an RTO of 15-20 minutes to restore a functional state, excluding DNS considerations.
  • failback has an RTO of 25-30 + X minutes to restore a functional state. Where X is the time it takes to back up and restore Elasticsearch, which is highly dependent on the setup and chosen Elasticsearch backup type.
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The described minutes for the Recovery Time Objective are estimated and may differ due to the manual steps involved.

Guides​

  • Familiarize yourself with our AWS setup guide that showcases an example setup in AWS by utilizing the managed Elastic Kubernetes Service (EKS) and VPC peering for a dual-region setup with Terraform.
    • The concepts in the guide are mainly cloud-agnostic and the guide can be adopted to other cloud providers.
  • Familiarize yourself with the operational procedure to understand how to proceed in the case of a total region loss and how to prepare yourself to ensure smooth operations.