Found by testing removal, which is the half nobody tests.
A grant was emitted for every secret the mesh held, whether or not the
machine still asked for it. So a consumer that was unassigned kept
appearing in its provider's manifest — and the provisioner's rule about
removing what nobody asks for can only fire if the mesh stops asking. The
login would have stayed live for ever, and nothing would have said so.
Skipped where the declaration is built rather than where grants are
gathered, so the rule holds whoever gathers them. No credential file is
written for a withdrawn consumer either, or the provisioner would find a
file its manifest does not mention and have to guess what that means.
The secret itself is deliberately kept. It is sealed and unusable to the
mesh, and a machine that comes back gets what it had — what withdraws the
login is the manifest, which is the thing that reconciles.
Two things, both found by trying to write a real postgres module and
discovering it could not be said.
A database has a superuser password, a broker an administrator, a
registry an account. None of them is *for* anybody — they are not the
credential a consumer is given, and the mechanism that hands those out
has a consumer in the middle of it. So a module may declare what it needs
and where to put it, and the mesh generates one per node, seals it, and
reads it no more than it reads any other.
Per node, deliberately: a module running on three machines has three
passwords. One in the manifest instead would put the same secret on every
machine that ever runs it, in a file anybody can read, for ever. Made
once and kept, or a running database would be handed a password it was
not started with; remade when the machine's sealing key changes, like
everything else sealed here.
A need declared and not made is refused rather than skipped, because a
module whose own credential is silently absent starts, fails to
authenticate, and the reason is three layers from the machine reporting
it.
And the provisioner can watch. That is what lets it be a module rather
than a binary somebody places: run once, it needs invoking after every
declaration by a timer or a unit wired to a file; watching, it is an
ordinary long-running service the host already supervises. It polls
rather than watching the filesystem, because the host writes atomically —
the file is replaced, so a watch on the path stops seeing anything after
the first replacement, and a watcher that silently stops working is worse
than a poll. Credentials are compared by digest and never held: this runs
for as long as the machine is up.
resolve.go had grown to 796 lines doing four jobs: working out what a
machine should run, applying settings, collecting contributions, and
placing credentials. They answer different questions — the first is
"what", the rest are "what does that look like as resources" — and one
file doing both is how a thing starts becoming the kernel everything
imports.
Prompted by looking at why HAL's shared library became unmaintainable.
Measured while here, and the shape is the inverse of that one: the large
packages import nothing internal, and only inventory and link compose. A
change to module resolution cannot reach connectivity, because
connectivity does not import it.
jschoubben