Relations between components

Overview

Component and span relations show the relationship between components in StackState. For example, the image below shows a relation running from a parent to a child component, that child also then has another component as a child component:

Service Name: Parent Component
|
---> Service Name: Child Component
     |
     ---> Service Name: Child 2 Component

An example of the above displayed in StackState will show up as follows:

These relations are based on the parent and child structure. A relationship is drawn from a parent component to a child component.

This means that:

• Service Name: Child Component has the parent ID set as Service Name: Parent Component

• Service Name: Child 2 Component has the parent ID set as Service Name: Child Component

Health state propagation

In StackState, the health state of a component will propagate upwards through the dependency tree. This means that in the following situation:

Service Name: Parent Component
|
---> Service Name: Child Component [400 Status]
     |
     ---> Service Name: Child 2 Component

The following components will have a propagated CRITICAL state:

Service Name: Parent Component [Propagated 400 Status]
|
---> Service Name: Child Component [400 Status]
     |
     ---> Service Name: Child 2 Component

A visual example of this in the StackState UI will be as follows:

So remember to create your parent and children spans in the correct order as it may affect the propagation of health state.

➡️ Learn more about health state propagation

Relations when merging

Relations are retained when merging components; this allows you to create a parent component, create a child component for this parent and then merge that child component with an existing component. This will then create a relationship between the pre-existing component that the child component merged with and the parent component. For example, here we have the three components as described above:

If we then merge our middle component Service Name: Child Component with the existing healthy Lambda component otel-example-custom-instrumentation-dev-create-custom-component in the bottom right corner:

• The middle component will disappear (merged with the Lambda component)

• The Lambda component will have relations to the first and third components (inherited relation mappings from the middle component).

Multiple children

It's also good to know that a single parent can have multiple children. This allows you to build a tree with branches of relations, for example:

Service Name: Parent Component
|
---> Service Name: Child Component
|
---> Service Name: Child 2 Component