Change: start sketch for implementation

1 files changed, 22 insertions, 1 deletions

diff --git a/contractor.md b/contractor.md
index f5bc869..d960a7b 100644
--- a/contractor.md
+++ b/contractor.md
@@ -9,6 +9,11 @@ author: "Lars Wirzenius"
 This document is in its very early stages, as is the whole Contractor
 project.
 
+## Open questions
+
+* How should the command line tool communicate with the manager
+  processes in the outer VM?
+
 # Introduction
 
 A continuous integration engine (CI) takes the source code for a
@@ -158,7 +163,10 @@ This high-level design is chosen for the following reasons:
 * it allows the build to happen in any operating system
   (**AnyBuildOS**)
 * the Contractor is a VM and running it doesn't require root
-  privileges; it has root inside the VM if needed (**NoRoot**)
+  privileges; it has root inside the VM if needed; all the complexity
+  of setting things up so the builder VM works correctly are contained
+  the outer VM, and the user need do only minimal configuration
+  (**NoRoot**)
 * the command line tool for using the Contractor can be made to be as
   easy as any build tool so that developer actually use it by default
   (**DefaultBuilder**)
@@ -197,6 +205,19 @@ The architecture leads to a build process that would work like this:
 * command line tool reports to the developer build success or failure
   and where build log and build artifacts are
 
+## Implementation sketch
+
+The outer VM runs Debian stable, and has libvirt to run guest VMs. The
+host and the outer VM are configured to support nested VMs, if the
+host hardware supports it. The outer VM has its networking configured
+so that it can connect to hosts outside itself, but the inner VM can
+only connect to services inside the outer VM. The services provided to
+the inner VM are an artifact store, and an HTTP proxy. (That's the
+only protocol I know of right now; more can be added if need be.)
+
+The artifact store is mounted to the outer VM using 9p. A web service
+in the outer VM serves the files to the inner VM. The developer can
+access the artifact store via their local file system.
 
 # Acceptance criteria