Configure Fargate Spot tasks (#7)

To reduce costs we setup ECS to deploy Fargate Spot
tasks along with on demand task. The idea is to ensure
that there is at least one fargate on demand task for
stability while all other tasks are run with spot tasks
for cost efficiency.

src/service_stack.py

@@ -152,6 +152,17 @@ def _get_secret(scope: Construct, id: str, name: str) -> sm.Secret:
                     )
                 ],
             ),
+            # Ensure at least one on demand task and the remaining should be spot tasks
+            capacity_provider_strategies=[
+                ecs.CapacityProviderStrategy(
+                    capacity_provider="FARGATE",
+                    base=1,  # At least 1 task will be run by FARGATE
+                ),
+                ecs.CapacityProviderStrategy(
+                    capacity_provider="FARGATE_SPOT",
+                    weight=1,  # The remain task will be run by FARGATE_SPOT
+                ),
+            ],
         )
 
         # Setup AutoScaling policy