Both of the things ADR 0141's insight named as remaining are built. A Go
toolchain based on a new mesh-tools-go module, so the compiler is named
and not pinned; and ${version} in any value of a resource that uses an
archive or a bundle.
Measured rather than asserted: the mesh built the host through its own
toolchain, published it to its own registry, and the bundle fetched back
out is a statically linked stripped binary that runs and says it is the
host.
The cost was larger again than 0141's note said. Three more things in the
path assumed one language or one shape — an entrypoint became a .ts file
whatever the language, the output directory was the compiler's to create,
and a bundle was refused if it named what it is built from — and a fourth
was in the base image, which is Alpine where the first Dockerfile ran
apt-get. That last one is issue 136 in an image, and the build refused
rather than a module failing later.
The version in a path is the digest, not the commit: two builds of one
commit are the same bytes, so a content-addressed version keeps the path
an unchanged build already had.
Still nothing delivers a version to a machine. The host module declares no
resources, so the bundle sits in the registry and no machine is asked to
take it. 0141 carries the insight and 142 the account.
The record claimed a version reaches a machine as an ordinary archive with
nothing new needed. Two things it needs do not exist: no toolchain can compile
the host (the list is typescript and python, and the control plane, also Go, is
built as an image from a Dockerfile instead), and nothing interpolates a built
version into a resource path, so nothing can ask for .../versions/<version>/.
The decision, the options weighed and every consequence stand — the host half is
merged and tested. What was understated was the cost, so it is corrected in place
and dated rather than superseded.
The supervision was already right — a clean exit means the host stood aside and
the launcher runs what is on disk, failures are counted, and a rollback happens
at the limit. Two things made it dead code: nothing told the running host a
successor was waiting, and the rollback resolved its known-good version through
pacman, which no machine here uses and which two of three operating systems do
not have.
Keeping a version rather than a path was the clue. Versions live side by side in
directories named for them; the newest runs; the running one stands aside between
reconciles; a reconcile that completes records itself and retires what is older
than its predecessor; rollback starts that predecessor. No new resource kind and
nothing new on the bus — an archive already fetches by digest, and the path
written is never the path executing.
Answers issue 142.
jschoubben