Camunda 8 - Enabling "Four Eyes" Review Process

Photo by Jason Goodman / Unsplash

A few weeks ago, there was a post on the Camunda forum that asked how you block access to a task if the user completes a prior task. This was a business need that we encountered in other BPM systems so we decided to include it in our Apex Designer Camunda 8 Library as well.

Business Scenario

A lot of business processes require multi-level reviews. In tax preparation it is common to have a 3 step process: Prepare, Review 1 and Review 2. This is sometimes called a “four eyes” review process. Here is a simplified form of a Prepare Return process:

Prepare Return Process
  • Prepare: The preparer prepares the tax return and submits it for reviews.
  • Review 1: A reviewer reviews the submitted return and submits it for a peer-review.
  • Review 2: Another reviewer reviews the reviewed return and approves it.

Managing Task Assignments

The bottom swimlane is titled "Reviewer". To implement this in Camunda, we add a Candidate Group of "Reviewer" to the activities Review 1 and Review 2. This ensures that only users with the "Reviewer" role can perform those review activities.

Review 1 Assignment

The Problem

Let's say that we have 2 reviewers - Tom and Ann - responsible for reviewing a tax return. When a user prepares a tax return and submits it, a Review 1 task is created. Both reviewers can see the task in their My Tasks view:

Review 1 task in Tom's inbox
Review 1 task in Ann's inbox

Either Tom or Ann can claim the task and review it. Let's say Tom performs the first review, which creates a task for Review 2. This new task will show up in My Tasks view of both the reviewers:

Review 2 task in Tom's inbox
Review 2 task in Ann's inbox

There is nothing preventing the Tom from reviewing it again. This violates the "four eyes" review.

The Solution

We handle this scenario by adding a custom header named “excludeUsersFromActivities”. It contains a list of activity ids. Users who completed those activities can not claim the task.


In the above example, any user who performed Review 1 shouldn't be allowed to review it again. So in the header of Review 2 activity, we added the key excludeUsersFromActivities with a value of Task_Review 1.

Solution in Action

Now let's submit another task for review, which will show up in the My Tasks view of both the reviewers:

Review 1 task in Tom's inbox
Review 1 task in Ann's inbox

The return is first reviewed by Tom, which creates the Review 2 task. The header “excludeUsersFromActivities” will ensure that the 2nd review task is not available for Tom.

Tom's inbox does not contain the new Review 2 task
Ann's task list does contain the new Review 2 task

Try it Yourself

The "excludeUsersFromActivities" handling is included in version 0.1.10 of the Camunda 8 Library in Apex Designer. You can read more about how Apex Designer works with Camunda 8 and how to try it yourself in this blog post.

Ashish Gupta

Ashish Gupta