Service vs. library: It's inner source, not inner deployment
Teams in a DevOps environment may be reluctant to work across team boundaries on common code bases due to ambiguity over who will be responsible for responding to service downtime. The solution is to realize that often it's possible to either deploy the same service in independent environments with separate escalation chains in the event of service downtime or factor a lot of shared code out into one library and collaborate on that.
When teams are working in a DevOps environment developers are responsible for a feature end-to-end: From the customer down to deployment, maintenance and support. This poses a challenge when working across team boundaries: Escalation chains may not be the same for errors happening in either team. Coupling source code and deployment leaves the teams with the question of who is responsible for on-call support in the event of errors. As a result teams are reluctant to join forces even if there is significant overlap in requirements.
Teams are working in a micro-services environment.
They are organised in full functional DevOps teams: Each team is responsible for their contributions end-to-end, including maintenance, on-call and customer support.
A team is tasked with providing a service to their downstream customers that is fairly similar to an existing service built by another team.
Organisational escalation paths may be different for each of the teams.
Members of each team may be unwilling to answer on-call support for errors that do not affect their own downstream customers.
Severity levels for the same types of errors may be different across team boundaries due to different SLA definitions per team/customer relationship.
Decouple responsibility for source code from deployment: Both teams work to identify exactly where there is overlap and synergies.
Only shared source code is kept as part of the InnerSource project with shared responsiblity.
Decouple configuration and deployment pipelines from actual business logic. Establish a second deployment of the service for the second team.
Treat the common base as a library that is used by both teams with shared code ownership.
Teams are willing to collaborate, benefitting from sharing the work of implementing the business logic.
A service that originally was built specifically to work in one environment is converted into a more general solution based on a specific business requirement.
Both teams get to know their respective escalation policy and deployment setup, potentially identifying improvements for their own setup.
The likelihood that changes are needed and made in the shared source code increases, leading to more frequent opportunities to refine, improve and optimise the implementation.
Related to this pattern is the Thirty day warranty pattern that takes a different approach to solving the forces described above.
Thank you Tobias Gesellchen for review internal to Europace AG.