Three additions, all written by trying to write a real database module
and finding out what could not be said.
A module may mirror an image it did not write. Naming an upstream
reference directly needs every machine to reach a public registry and
pins to a tag somebody else can move.
A module may need a secret of its own — a superuser password is not FOR
anybody, so the mechanism that hands credentials to consumers cannot
express it. Per node, so three machines have three passwords.
And the provisioner watches, which is what lets it be a module rather
than a binary somebody places. It polls rather than watching the
filesystem, because the host writes atomically and a watch on a replaced
path silently stops working.
One assignment now gets a working database provider: two directories, two
pinned containers, a sealed password and the grants manifest.
Two additions to the module-repository design, both from building it.
A build machine has its own credential and it is not a node's: read the
build queue, write the mesh exchange, nothing else. A node's queue
carries that node's declarations.
The answer goes through the exchange and never the default one, because
permission there is per exchange rather than per queue — anything allowed
to use it can publish into any node's queue. The price is that every
asker sees every result and filters by correlation, which is cheap
against a builder never needing that permission.
And every result is kept, failures included, because one that leaves no
trace is indistinguishable from a build nobody asked for. That is what a
builds view reads; the board page is corrected to say so.
A build is work, not state, and that is why it does not travel as a
declaration: as one it would either rebuild on every reconcile or carry
"and I already did this", which is state about an event rather than about
a machine. So it has its own queue and the answer comes back correlated.
Three properties recorded because they are decisions: acknowledge only
once the answer is away, one build at a time, and a failure is a result
rather than silence.
And the board page is corrected. A build result today is answered to
whoever asked and kept nowhere, so a builds view has nothing to read. A
record of past builds is the missing piece, not the builder.
Designed with no reference to what came before, which was asked for. The
system this replaces has features — several deployable units inside one
module — and they are deliberately absent.
That closes something ADR 0001 has been carrying as an open prerequisite.
It lists "named features with per-node opt-in" as required, or "every
independently deployable unit becomes a module again and the count
returns". The premise was right and the remedy already exists in another
form: several modules, assignment per node, and a module with
requirements and no files of its own. `networking` is exactly that. The
count does not return because what made it return — a module is
expensive, so put several things in one — is gone. A module here is a
manifest and usually nothing else.
The manifest in a repository names artifacts; the manifest the mesh holds
names digests. Two documents, because a digest is not knowable until
something is built and a repository carrying one is wrong the moment
anybody edits anything.
The builder runs on a node. Building needs a container runtime and a
working tree, and what the control plane may send a machine is bounded by
the declaration language. A control plane holding a container socket
would be the one component that can do anything anywhere.
And the host's vocabulary grew from six shapes to eight — user and
archive — with the reasoning for each and for the refusals that came with
them. The count is asserted by a test precisely because every addition
widens what a compromised control plane can express.
jschoubben