Software Architecture

Fitness Functions for Governance

Applying the Flatten Components decomposition pattern involves a fair amount of subjectivity. For example, should code from leaf nodes be consolidated into the root namespace, or should code in a root namespace be moved into leaf nodes? That said, the following fitness function can assist in automating the governance of keeping components flat (only in leaf nodes).
Fitness function: No source code should reside in a root namespace
This automated holistic fitness function can be triggered on deployment through a CI/CD pipeline to locate orphaned classes—classes that reside in a root namespace. Use of this fitness function helps keep components flat when undergoing a monolithic migration, especially when performing ongoing maintenance to the monolithic application during the migration effort. Example 5-6 shows the pseudocode that alerts an architect when orphaned classes appear anywhere in the codebase.
Example 5-6. Pseudocode for finding code in root namespaces
# Walk the directory structure, creating namespaces for each complete path

LIST

component_list

=

identify_components

(
root_directory
)


# Send an alert if a non-leaf node in any component contains source files

FOREACH

component

IN

component_list

{

LIST

component_node_list

=

get_nodes

(
component
)

FOREACH

node

IN

component_node_list

{

IF

contains_code

(
node
)

AND

NOT

last_node

(
component_node_list
)

{

send_alert
(
component
)

}

}

}