novox/hq 04-ISSUES/022. A credential was keyed by provision, consumer
node and provider node, so "who is asking" was answered by naming a
host. The node this mesh exists to take over runs eight modules against
one database server.
The symptom had two halves and only one was loud. The provider refused,
naming the modules and explaining they would share one credential, which
reads as a decision rather than a limit. The consumer did not refuse: it
resolved cleanly, wrote one module's credential file and left the others
absent — a service that starts and cannot authenticate, with nothing
saying why. That is 021 again on a different axis.
Three modules wanting one database produced one need, carrying whichever
module mentioned it first, because the resolution walk is a work-list
over names. The fan-out now happens in one place, after the walk. The
record path already did this correctly and said why: a consumer here is
a module on a machine. It is the same rule.
Downstream: the secret's key gains the consuming module, the grant file
is named after both halves, needs are matched by provision and module
rather than provision alone, and the provisioners name the role and the
access key after the module. The refusal in ContributionsTo is gone
because there is nothing left to refuse.
Worth stating plainly: without that refusal, gitea's login would have
opened keycloak's database. From the provisioner's side it created
exactly what it was asked to create.
Existing secrets are discarded rather than backfilled. They cannot say
which module they were for, and a secret is remade and delivered to both
ends on the next push — so this costs one rotation and invents nothing.
Also guards the role name against PostgreSQL's 63-byte truncation, which
is a notice rather than an error and would reintroduce exactly this
collision at a length nobody tests.
Three faults injected — the fan-out removed, needs matched by name
alone, the grant file named after the machine — each caught.
Provisions were named after roles: provides "database", requires
"database". Nothing distinguished engines, so a module written against
PostgreSQL could be matched to a provider of SQL Server, resolve as
satisfied, deploy, and fail on its first query — with nothing
connecting that error back to a match made elsewhere by something that
believed it had done its job.
The failure is in the direction that hides. Refusing on ambiguity
exists precisely so this does not happen, and the generic name walked
around it: with one provider of each name nothing is ambiguous, so
nothing is asked.
How it got in: every resolver test had exactly one provider per name,
so no mismatch was expressible and none was caught. The fixtures agreed
with the design — the same fault as the imagined test output in
04-ISSUES/005, at the level of a name.
Refused rather than documented, because the old naming *was* the
documented convention. Providing database/db/sql/sql-database is now a
parse error naming what to write instead.
The rule is about coupling, not specificity everywhere: route and
resolver stay role-named, because a consumer genuinely cannot tell
which proxy answered. novox/hq ADR 0027.
Knowing that a machine needs the anchor's database is useless to the
program that needs it unless the program is told. It knew; nothing was
written anywhere it could read.
Two fields, mirroring contributes/receives in the other direction:
serves: {database: {port: 5432, driver: postgres}} on the provider
binds: {database: /etc/app/database.json} on the consumer
The provider says what a consumer needs to know; the mesh adds the half
only it has — which machine, and what that machine is called on the
private network. The file says, in itself, that it carries no credential
and why. A missing field looks like a bug; a stated absence looks like a
boundary.
Binding something answered on this machine writes nothing. A file saying
"it is on this node" is a fact nobody needs and one more thing to keep
true.
And two machines that share no private network are refused rather than
wired together. An app here and a database there with no path between
them is a mesh that reports itself configured and does not work — the
failure surfaces as a connection timing out, which is the slowest place
to find it. This is checkable now only because the network became
something a machine is given rather than something it has by having an
address.
One fault, found by running it: working out who is on the private network
resolved the mesh, and resolving the mesh asks who is on the private
network. It hung for two minutes. The comment above the function said not
to do that and the function did it anyway; it now resolves each node
locally, which is the right answer to the question regardless — whether a
machine is on the network depends on what it was assigned, not on what it
takes from others.
Two different things were both written `requires`. A shell, a display
server and a private network have to be on the machine that needs them.
A database does not — it runs somewhere and is reached over the network.
Both were answered the same way, so requiring a database installed
PostgreSQL on every machine that ran a web application.
What a module provides now carries a scope, the same idea claims already
use, written short in the ordinary case:
"provides": ["shell"]
"provides": [{"name": "database", "scope": "mesh"}]
A mesh-scoped requirement is answered by finding the node already running
it — never by installing it here. Choosing a machine to put a database on
is a decision with consequences, and nothing resolving a web application
should make it silently. With nothing anywhere it refuses and says which
module to assign; with two it refuses and says how to choose.
Choosing is `pin <node> <provision> <from>`, kept per node because that
is the granularity the choice has. A pin at a machine that does not
provide it refuses rather than falling back — a fallback would quietly
move somebody's data. One provider does not overrule a pin either.
Resolving a node now needs to know what the others offer, and working
that out needs them resolved, so it is two passes: the first answers only
what each node offers, the second answers everything. Nothing is ever
declared from the first.
A node's plan says what it takes from elsewhere. It is the only part of a
set that stops working when a different machine goes away, and nothing
else in that output would have said so. It is also where a credential
will hang once there is a mechanism for handing one back.
One test found passing for the wrong reason: it read pins through a join
on the provider, which hides a dangling row whether or not it was cleaned
up. It counts rows now, and bites when the cascade is removed.
jschoubben