Initial docs commit

2016-08-18 21:37:52 -07:00
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+
+A high level view of the internals of Fission.
+
+Components
+==========
+
+Language-neutral components:
+
+ * Controller
+ * Container Pool Manager
+ * Container Specializer
+ * Router
+
+Language-specific components:
+
+ * Language Build Container
+ * Language Run Container
+
+
+Controller
+----------
+
+Function and Trigger CRUD APIs.  APIs to watch for changes are also
+included (useful for other components that cache state).
+
+See api/swagger.json for API details.
+
+This is the only stateful component.  It needs to be configured with a
+URL to an etcd cluster and a path to a persistent volume.  The volume
+will be used to store the functions' source code.
+
+Etcd is used as the DB.
+
+
+Container Pool Manager 
+----------------------
+
+Manage pool of generic containers.
+
+Probably use K8s RCs.  Can we Use labels to move pods from one rc to
+another?  What about jobs?
+
+Container Specializer
+---------------------
+
+Inputs: a running generic language run container, a user function,
+optionally an http trigger URL.
+
+Calls Language Run Container and sets up Router to point to it.
+
+
+Router
+------
+
+- Cache trigger -> container instance mapping; implement cache miss and expiration.
+
+- Invoke Specializer, setup up k8s API 
+
+- Forward requests
+
+The Router is stateless -- it can be scaled or killed at any time.
+
+There's a lot of functionality overlap with K8S Ingress Controllers.
+We should clearly use Ingress and Ingress Controllers in some way.
+It's not exactly clear at the moment how -- should make a whole new
+Ingress Controller perhaps based on the contrib/nginx
+
+
+Autoscaler
+----------
+
+This autoscales the language run containers that are backing a
+trigger.
+
+What metrics this is based on is TBD.
+
+- Number of requests/sec
+- "Backlog" -- number of outstanding requests not yet started -- how to measure this?
+- Change in turn-around time?
+
+
+Language Build Container
+------------------------
+
+* The Language Build Container is a container that is invoked for a
+  build.  It takes one user-created function and outputs something
+  that can be run by the corresponding Language Run Container.
+
+* The Build Container must implement the Language Build Container
+  interface.
+
+
+Language Run Container
+----------------------
+
+* The Language Run Container is the container in which user functions
+  run.
+
+* The Run Container is started without the user function.  It must
+  start as a "Generic Container".  It must implement the
+  "specialization interface".  In short, it must implement an HTTP
+  server that can receive a piece of code, verify its signature, and
+  map it to an HTTP endpoint.  See
+  Documentation/specs/LanguageRunContainerSpec.md for details.
+
+
+