Building Microservices: Designing Fine-Grained Systems

by Sam Newman

In another pattern from Release It!, Nygard introduces the concept of a bulkhead as a way to isolate yourself from failure. In shipping, a bulkhead is a part of the ship that can be sealed off to protect the rest of the ship. So if the ship springs a leak, you can close the bulkhead doors. You lose part of the ship, but the rest of it remains intact. In software architecture terms, there are lots of different bulkheads we can consider. Returning to my own experience, we actually missed the chance to implement a bulkhead. We should have used different connection pools for each downstream connection. That way, if one connection pool gets exhausted, the other connections aren’t impacted, as we see in Figure 11-3. This would ensure that if a downstream service started behaving slowly in the future, only that one connection pool would be impacted, allowing other calls to proceed as normal.

Bulkhead