I encountered this issue on an upgrade of IAM, it wasn't covered in the documentation.

Kong is prompting to have the postgres DB structure updated to match the newer version of Kong. I solved it by changing the docker-compose.yml to contain the following config to run 'kong migrations up', then started the container:

  iam-migrations:      image:${ISC_IAM_IMAGE}      command:kongmigrationsup      depends_on:        -db      environment:        KONG_DATABASE:postgres        KONG_PG_DATABASE:${KONG_PG_DATABASE:-iam}        KONG_PG_HOST:db        KONG_PG_PASSWORD:${KONG_PG_PASSWORD:-iam}        KONG_PG_USER:${KONG_PG_USER:-iam}        KONG_CASSANDRA_CONTACT_POINTS:db        KONG_PLUGINS:bundled,jwt-crafter        ISC_IRIS_URL:${ISC_IRIS_URL}      restart:on-failure      links:        - db:db