jschoubben
7553af6c5a
Everything is blocked on what a node presents to prove which node it is. This builds the other direction, which is not blocked: what a node believes. identity is the second of the seven contexts. It holds an Ed25519 signing key the control plane generates once, whose public half now travels in every enrolment token. A node believes a declaration because it carries a signature that key made -- pinning only the broker would make the control plane's authority transitive, and since the host applies whatever the link delivers, a compromised broker forging declarations is the whole machine. Establishing the key is idempotent, and it has to be: a second key generated by a restart is a mesh where every node holds the wrong public half, so every declaration is refused by every node with nothing visibly wrong. The guarantee is a partial unique index plus a read-back, not the check before the insert -- six processes racing to establish all agree on one key, and there is a test that runs them. Tokens are now one line of base64 carrying three of their four parts. The missing two are the broker's address and its certificate fingerprint, both step 5 of the bootstrap. The command prints the token and names what is missing rather than emitting something that looks usable. The second context also tests a claim this repository had made and never checked: that a context reaches only its own store. Two databases, two credentials, no setting that reaches both. Running migrate with one stops and names the grant it lacks -- verified, not asserted. Assembling a token needs a node record from one and a key from the other, and neither reads the other's store; the process holding both grants asks each for its part. 45 tests, none skipped. Fault injection found one test whose property is enforced somewhere other than where I injected -- idempotency comes from the database constraint, not from the early return, which is what the code comment already said.
8.6 KiB
mesh-control
Tier 2 of Novox Mesh — the control plane. Everything that needs to know about more than one node.
That is the whole test, and it draws the line the host cannot: the host applies and does not decide, because deciding needs knowledge one machine does not have. Which nodes should run the store, which peers belong in an overlay, whether a node has been unreachable for a week — nobody on a single machine can answer any of them.
The reasoning lives in novox/hq; this repository carries no argument that is not settled there.
What it is not
- Not the thing that changes machines. It decides; the host applies. It never reaches into a node except through the host, over the link, in a bounded vocabulary.
- Not a database. There is no mesh database. Each context owns its own store and nothing outside a context touches it — including nodes, which hold no credential to any of them.
- Not privileged. It has no more access to a machine than a declaration can express.
What exists today
One context of seven, and one of the things it will do.
inventory |
node records and enrolment tokens — built, as far as identity |
identity |
the control plane's own signing key — built, and no further |
config, connectivity, provisioning, delivery, observability |
not built |
| the interface every surface speaks to | not built; its shape is not decided |
mesh-control migrate bring each context's schema up to date
mesh-control node add <name> create a node record
mesh-control node list the nodes this mesh knows about
mesh-control token issue --node <name> a one-time right to join, for an existing record
mesh-control token issue --new <name> create the record and issue for it
mesh-control identity show this control plane's signing key
mesh-control version what this binary is
migrate is step 3 of the substrate bootstrap — the step the first node cannot get past, run
against a database raised moments earlier from the bundle the host carries.
Tokens, and what they are missing
A token is a one-time right to join, issued for a node record — which is where re-enrolment is decided, since what an identity binds to is settled when the token is made rather than when it is presented.
What is built: the secret is 256 bits from the system's random source, shown once, and stored only as a hash, so a copy of this database is not a set of working credentials. It is usable exactly once and only before it expires, and both are read from the row rather than from a status something would have had to write. Issuing again for the same node invalidates the outstanding one — two live tokens are two machines able to join as the same node.
Redemption is a single statement that both finds a live token and spends it, so eight concurrent attempts on one secret produce exactly one winner. There is a test that runs them.
A token now carries three of its four parts, and is one line of base64 a person can copy. The signing key is real: an Ed25519 key this control plane generates once and keeps, whose public half travels in every token. A node believes a declaration because it carries a signature that key made — and pinning only the broker would not do, because it would make the control plane's authority transitive, so a compromised broker could forge declarations, and since the host applies whatever the link delivers that is the whole machine.
Still missing: the broker's address and its certificate fingerprint. Both are step 5 of the
substrate bootstrap and neither exists. token issue prints the token and names what is
missing, rather than producing something that looks complete and cannot be used.
Two contexts, and the rule between them is real
identity is the second context and it exists partly to test a claim this repository had made and
never checked: that a context reaches only its own store. It holds MESH_STORE_IDENTITY;
inventory holds MESH_STORE_INVENTORY; there is no setting that reaches both and no way to ask
for one. Run migrate with only one and it stops, naming the grant it does not have.
A token needs a node record from one and a signing key from the other. Neither reads the other's store — the process holding both grants asks each for its part.
Where this stops, and why there
At identity. A node's own identity is the next thing needed and its cryptographic form is not decided anywhere: whether a node holds a keypair whose public half the mesh keeps, or something else. Modelling it would have meant guessing, in a migration — which is the most expensive place in this system to guess, because a schema that ran is finished and the only way back is another migration.
So the node table holds what a node record is — a name, when it was made, what the machine last reported about itself, when it was last heard from — and stops before what a node presents.
Reaching a store
A context is granted only what it exclusively owns. No shared writes, no read-only role on another context's store, and no connection string that reaches more than one.
That is a rule about credentials, so it is built as one. There is no mesh-wide connection setting and no way to ask for one:
MESH_STORE_INVENTORY=postgres://…/inventory
A process granted inventory holds that variable and no other. Reaching another context's store
is not a matter of restraint — it has no address for it and no credential to present. And it is
how the rule is checked: what a context can reach is visible in the declaration that runs it,
as the list of variables it was given.
Each context's database is named after the context. There is deliberately no database named for the mesh as a whole.
Migrations
Numbered, embedded in the binary, applied in order, each in a transaction with the row recording it. The applying is four lines; the rest is refusals, and the refusals are the point:
| it stops when | because |
|---|---|
| a migration that ran has since been edited | the database holds the old version, the repository holds the new one, and nothing holds the difference |
| a migration is numbered below one that already ran | usually two branches taking the same next number — applying it now runs the schema in an order nobody tested |
| two migrations share a number | order is the entire guarantee, and two files with one number have none |
| a file in the directory is not a valid migration name | a misnamed migration would otherwise never run and nothing would say so |
| a migration is empty | it records that something happened and changes nothing, which cannot be told from a mistake |
All of them stop rather than warn. At the moment any of them is true, nobody knows what the database contains, and there is no correct guess about a schema.
Running it again does nothing. Two copies running at once take an advisory lock, so a restart during a slow migration does not become two runners racing.
Building
make build the binary
make image the container image
make check gofmt, vet, and every test against a real PostgreSQL
make check raises a throwaway PostgreSQL in a container and takes it down afterwards, including
when the tests fail. Without one the tests that need a database skip and say so rather than
passing quietly — make test is the honest subset, not the gate.
Tests run against a real database rather than a fake because what is being tested is the database's behaviour: that DDL is transactional, that an advisory lock serialises, that a checksum mismatch is caught against a record PostgreSQL actually kept. A fake would assert that the fake behaves as expected.
Every test here has been confirmed to fail when the behaviour it defends is removed. Two did not, when first written, and both are now commented with what they were missing.
The image
FROM scratch, holding one statically linked binary and nothing else — no shell, no package
manager, no libc, no CA certificates.
Not a size optimisation. The bundle a host carries pins this image by digest, and it is fetched and run on a machine where no mesh exists to check anything and a person is expected to have read the bundle and believed it. Everything in the image is something that person would have to audit.
Where the reasoning lives
| what the control plane is | novox/hq ADR 0006 |
| what it takes to run one, and why Go | novox/hq ADR 0006 |
| a context owns its store, exclusively | novox/hq ADR 0008 |
| schema changes are numbered migrations | novox/hq ADR 0013 |
| a test defends a decision | novox/hq ADR 0017 |