- https://martinfowler.com/articles/richardsonMaturityModel.html
- The 3 levels of REST maturity - level 3 requires HATEOAS and is a prerequisite for proper REST
- https://spring.io/understanding/HATEOAS - explains HATEOAS simply
- http://www.springboottutorial.com/spring-boot-vs-spring-mvc-vs-spring - simple explanations
- PCF is a set of apps installed on VMs run in public or private clouds
- It abstracts away the underlying IaaS across multiple cloud providers by focusing on their common denominator -- VMs
- By doing this it provides a PaaS for rapid cloud development -- dev against PCF, deploy onto any CSP where we installed PCF
- Ex: an AWS or Azure cloud in a certain geographic region may have a set of VMs on it leased by a company
- The company installs PCF onto these VMs
- The company goes into PCF and establishes orgs and spaces
- Orgs: logical groupings of compute resources
- Spaces: within orgs, ex: dev, qa, prod spaces (custom names) -- we create spaces within orgs
- Apps live in spaces, spaces live in orgs, orgs live in a PCF instance
- Apps and services are not shared between spaces -- they are bound to a specific space
- This makes for cleaner installs, no shared data/state
- Each app in PCF can have one or more services bound to it
- This injects some runtime environment variables into the app during the provisioning process
- These in turn configure PCF to autoconfigure some components (beans in Spring Boot) into the app
- PCF consists of over 15 specialized apps, originally written in Ruby then rewritten in Go
- Diego Brain service allocates resources within the PCF
- CF Router facilitates routing and service registry within PCF
- The Cloud Controller exposes a REST interface -- can interact with it programmatically via the CLI
cfcommand - The UAA is an OAuth2 server within PCF
- Client request flow:
- Client submits request
- Request first hits a load balancer -- usually F5 load balancer
- F5 distributes request to a chosen GoRouter
- GoRouter in turn acts as load balancer for a set of container apps
- GoRouter monitors health of the container, if it is maxing memory/etc and autoscaling is set up the GoRouter can spin up a new container by coordinating with Diego Brain to access a VM from the VM pool
- Other PCF services such as Health Monitor facilitate service orchestration
- Use
cf pushin the home dir of the app - What this does
- CLI sends request to Cloud Controller to create the app
- CLI uploads the app to the Blob Store
- CLI sends requests to Diego Cell which allocates reources & starts the app
- It also checks for buildpacks appropriate to the app
- These provide runtime support for the app
- It determines which buildpacks to use by scanning the app directories and looking for certain signatures
- e.g. if it detects python code it uses the python buildpack, etc
- We can also specify which one to use in case PCF can't determine which to use
- Can view app instance health - running, memory, space, etc.
- Loggregator is a log viewer that shows consolidated logs from all app container instances