Issue 117: a module's own code is a container in one record and a process in another #110

Merged
jschoubben merged 3 commits from issue/117-a-modules-own-code-is-a-container-and-a-process into main 2026-09-26 12:14:38 +00:00
3 changed files with 388 additions and 0 deletions
@@ -0,0 +1,86 @@
---
status: open
opened: 2026-09-24
located-in: [mesh-controller module.json, mesh-host internal/apply]
fixed-by:
amended-design:
---
# 114 — Should the controller run as a container, or as a process the host supervises directly?
## What was observed
On the control-node, 2026-09-24, over a long session of operating the mesh through
`mesh-controller`'s CLI (build, push, plan, status, module moved). Every mutating step reached the
binary the same way: `docker exec mesh-controller /mesh-controller <command>` — because
`mesh-controller`'s own manifest declares its one resource as:
```json
{ "id": "server", "type": "container", "name": "mesh-controller", "network": "host", "args": ["serve"] }
```
Two things about that declaration are worth naming together, because neither is a problem on its
own and the combination is what raises the question:
- **`network: host`.** The controller does not use container network isolation, which is the
property a `container` resource type usually buys over a `process` one. It runs with the node's
own network namespace either way.
- **It is the mesh's single point of coordination.** [`03-DESIGN/01-to-be/06-the-controller.md`](../../03-DESIGN/01-to-be/06-the-controller.md)
is explicit: "one node runs it, and nothing takes over" — no election, no quorum, no failover;
recovery is restore, not failover.
[ADR 0005](../../02-DECISIONS/0005-the-node-host.md) gives the host — the one thing tier 0 requires
to be a real system daemon — exactly this reasoning for refusing to run in a container: *"installing
the container runtime is a step of the bootstrap, so a host inside a container would need the thing
it exists to install."* The controller is one tier up and does not install the runtime, but it
shares the profile that argument turns on: something the rest of the mesh's operation depends on,
sharing fate with a runtime that is not itself.
## Why it matters beyond this instance
Practically, tonight: every controller interaction was raw shell into a container (`docker exec`),
not a first-class surface — no logs command beyond `docker logs`, no `systemctl status`, and a
session permission classifier that (correctly) treats arbitrary shell into a container as needing
sign-off every time, unlike an ordinary supervised process. That friction is a symptom, not the
issue itself.
The actual question is whether `type: container` is buying the controller anything here besides
image-based delivery and a restart policy — both of which [ADR 0005](../../02-DECISIONS/0005-the-node-host.md)'s
launcher pattern already describes as buildable directly into the host's own supervision (restart on
exit, count consecutive failures, roll back after too many, halt after that), for the host's own
unit. If the controller were declared `type: process` instead — still built and versioned through
the same delivery pipeline, just executed on the node and supervised by the host the way the host
supervises itself — it would stop sharing fate with the container runtime's health (restarts,
upgrades, disk pressure evicting containers) for the one piece of software whose absence the rest of
the mesh is designed to tolerate but nothing is designed to *want*.
This is squarely a question, not a claim that today's shape is wrong: [ADR 0006](../../02-DECISIONS/0006-the-substrate-and-the-control-plane.md)
already tolerates the controller being down by construction (nodes reconcile from their own
last-applied state), which may make the container-runtime coupling moot in practice. Nobody has
checked.
## Open questions
- Does `mesh-host`'s `process` resource type already support the restart/failure-counting semantics
[ADR 0005](../../02-DECISIONS/0005-the-node-host.md) describes for the host's own launcher well
enough for something this central — or would this need host-side work first?
- With `network: host` already in use, what does `type: container` provide the controller today that
`type: process` would not?
- Is there a real circularity risk — the controller's own health depending on the container runtime
it (indirectly, via the host) manages — or does "one node runs it, nothing takes over" already make
a controller outage tolerable regardless of which resource type it is?
- If the answer is "keep it a container," what does that answer, precisely, that this issue asked —
so the next person who notices the same asymmetry finds it answered rather than open again?
## The general case
[Issue 117](../117-a-modules-own-code-is-a-container-and-a-process/00-report.md) is the same
question asked of every module rather than of the controller: a module's own code is a `container`
in [ADR 0047](../../02-DECISIONS/0047-a-module-runs-its-code-as-its-own-process-with-its-own-account.md)
and a `process` in the to-be design, and no record moves it. Its
[diagnosis](../117-a-modules-own-code-is-a-container-and-a-process/01-diagnosis.md) answers the
first open question above: the host's `process` shape is built, applied and tested, including the
restart and run-to-completion semantics — so this would not need host-side work first.
The two do not collapse into one. The controller is not a code-carrying sidecar, and `network: host`
is what makes the asymmetry visible here and nowhere else.
@@ -0,0 +1,101 @@
---
status: located
opened: 2026-09-25
located-in: [hq, mesh-catalog modules/showcase, mesh-sdk src/tools/index.ts, mesh-tools]
fixed-by:
amended-design:
---
# 117 — A module's own code is a container in one record and a process in another
## What was observed
Asked what the "sidecar" is — the second container a code-carrying module runs beside its
service — and whether a supervised process would do instead. Reading the records to answer it,
the repository answers both ways, and nothing reconciles them.
| record | status | what runs a module's own code |
|---|---|---|
| [ADR 0047](../../02-DECISIONS/0047-a-module-runs-its-code-as-its-own-process-with-its-own-account.md) | **accepted**, 2026-09-04 | "a **container**, the tool runtime carrying that module's compiled code" — one module, one process, one account; events and tools in that same process, "not a second one to scope and seal" |
| [`01-to-be/18-building-a-module.md`](../../03-DESIGN/01-to-be/18-building-a-module.md) | proposed, 2026-09-21 | a resource type table in which `container` is "an image" and **`process`** is "**its own code**, in three modes", whose default mode is "a unit restarted when it exits", supervised by the machine |
| [`01-to-be/20-writing-a-module.md`](../../03-DESIGN/01-to-be/20-writing-a-module.md) | proposed, 2026-09-21 | one module declaring **four** `process` resources — events, tools, provisioner, a scheduled ingest — each with its own `run` argv, and the sentence "it is why these are `process` rather than four containers" |
Three disagreements, not one:
1. **Container or unit.** ADR 0047 chose a container and said why: a node-wide runtime loading
every module's code could not hold a per-module account, so the runtime is per-module. The
design docs choose a supervised unit running an argv and give no reason, because they do not
record that they are choosing.
2. **One process or several.** ADR 0047's "one module, one process, one account" is the whole
content of its second and third sections. The worked guide declares four for one module and
presents four as the point.
3. **Whether the record was consulted at all.** Neither design doc names ADR 0047 in
`decisions:`. No record supersedes or extends it on this. **The string `process` as a resource
type appears in no decision record** — the shape exists only in two `proposed` design docs.
Meanwhile the thing as built is the container. [ADR 0029](../../02-DECISIONS/0029-a-network-is-a-shape-because-an-action-cannot-be-undone.md)
records that "anything that is a service plus a sidecar currently has to publish a port to talk
to itself," which is one of the things the host's `network` shape was added for.
[Issue 113's diagnosis](../113-the-object-stores-images-were-withdrawn-upstream/01-diagnosis.md)
found a catalogue module declaring "two container resources," the second a runtime sidecar
"pinned at an all-zeros digest, meaning nothing was ever published for it."
[Issue 095](../095-a-module-assigned-after-genesis-has-no-broker-account/00-report.md) is a
sidecar crash-looping on a credential while its service served correctly.
[ADR 0093](../../02-DECISIONS/0093-a-fixture-that-runs-a-modules-runtime-carries-its-name.md)
records that a bed wanting "a sidecar without its server raises the server."
### And the word is in no glossary
"Sidecar" appears sixteen times across five records — two decisions and three issues. It is
absent from [`00-META/glossary.md`](../../00-META/glossary.md), and absent from every document
under [`03-DESIGN/`](../../03-DESIGN/), in both layers. ADR 0047, which creates the thing, never
uses the word; it says "runtime process" and "runtime container". The glossary's own rule is that
"a new name for an existing thing lands here first, in the same change that introduces it in
code," and the page exists because "the terms kept drifting in conversation." A reader asking
what the sidecar is has nowhere in the design layer to look, which is how this was found.
## Why it matters beyond this instance
- **A module author reading the current guide writes a `process`; the catalogue as built declares
a `container`.** [`20-writing-a-module.md`](../../03-DESIGN/01-to-be/20-writing-a-module.md) is
a worked guide with a manifest in it. Whichever of the two is wrong, somebody follows it.
- **The cost of the container shape is paid in four places and totalled in none.** A published
image per code-carrying module, a network so a module can reach itself, a bed that cannot run a
runtime without raising the server it manages, and a credential failure that presents as the
module's own bug. Each record argues its own piece is worth paying. No record puts them beside
the alternative.
- **Both shapes carry a cost the other does not, and neither is written down.** A container
carries its own interpreter; a `process` declaring `run: ["node", "index.js"]` needs an
interpreter present on the machine, which is the machine dependency the statically linked host
([ADR 0005](../../02-DECISIONS/0005-the-node-host.md)) exists to avoid. And `run` is an argv,
where [ADR 0005](../../02-DECISIONS/0005-the-node-host.md) refuses `action` because the link may
not carry a command — a refusal [`18-building-a-module.md`](../../03-DESIGN/01-to-be/18-building-a-module.md)
restates on the same page that it introduces `process`.
- **This is the repository's own named failure mode, in its own records.** `cycle.py` enforces
that a to-be doc names *at least one* decision. Both docs do, so both pass, while introducing a
resource type no decision records and contradicting an accepted one. The rule is "no design
without a decision"; the check is "no design without *a* decision." An unenforced rule is
indistinguishable from a wrong one, and these two documents are what that gap looks like when
something walks through it.
## Open questions
- Which is the decision — container or supervised unit? If the design docs are right, ADR 0047
needs superseding rather than quietly outliving. If ADR 0047 is right, two proposed documents
and a worked manifest describe a resource type that does not exist.
- Is one account per module satisfied by a per-module *unit* as well as a per-module *container*?
ADR 0047's argument rules out a node-wide runtime sharing one account. It does not appear to
rule out a unit holding one scoped credential, and nothing has said so either way.
- If several processes for one module are right, what holds the accounts? ADR 0047 refused "a
second one to scope and seal" for events beside tools. Four processes are four somethings.
- How does a `process` get its interpreter, and does declaring one reintroduce the machine
dependency the host is built to avoid?
- Is `run` an argv the link may carry, given `action` is refused for being one? If the answer is
that a `process` reconciles and an `action` does not, that distinction is not written down.
- What is the thing called, and where does the design layer describe it? Whichever shape wins, no
document in either layer currently says a code-carrying module runs a second thing beside its
service.
- **How would this have been caught?** A decision and a design doc disagreeing on a resource type
is mechanically checkable: the resource types a design doc names are a closed set, and every
member of it either appears in a decision or does not. Whether that check is worth writing is
part of this issue, not settled by it.
@@ -0,0 +1,201 @@
# Diagnosis — 117
## Which trees were searched, 2026-09-25
Named first, because [issue 113](../113-the-object-stores-images-were-withdrawn-upstream/01-diagnosis.md)
is the record of reporting absence in one repository as absence in the mesh.
| Searched | At |
|---|---|
| `mesh-host`, `mesh-catalog`, `mesh-tools`, `mesh-sdk`, `mesh-controller` | `main`, fresh shallow clones |
| `hq` | `main`, and the two branches named under finding 7 |
**Not searched:** the private migration repository; the open pull requests on the catalogue and
the controller; any branch of a code repository other than `main`. A statement below about "the
catalogue" is a statement about its `main`.
## The report's central question is answered: the shape exists
`mesh-host` `internal/declaration/declaration.go` defines `TypeProcess Type = "process"`.
`internal/apply/process.go` applies it — it writes the unit, writes the timer for a scheduled one,
and gates what follows a run-once one. It has tests of its own in both packages. The resource
carries a bundle `source` with a `digest`, a `run` argv, `env` and `env-file`, a `user`,
`restart-on`, and the `run-once` and `schedule` modifiers.
So the report's alternative — "if ADR 0047 is right, two proposed documents and a worked manifest
describe a resource type that does not exist" — is **disproven**. It exists, it is implemented, it
is tested, and the host's vocabulary is now **twelve** shapes rather than the nine
[ADR 0029](../../02-DECISIONS/0029-a-network-is-a-shape-because-an-action-cannot-be-undone.md)
counted.
## The enforcement ADR 0029 asked for is intact, and it recorded this gap rather than closing it
ADR 0029 said "the vocabulary is nine, and the count moves with a record. The test that asserts it
names this one." That test exists — `internal/declaration/declaration_test.go` asserts the count is
twelve and fails with the reason rather than a number. Above the assertion, a paragraph per
addition names what made it one:
| shape | the test names |
|---|---|
| `network`, ninth | ADR 0029 |
| `access`, tenth | ADR 0051 |
| **the eleventh** | **`03-DESIGN/01-to-be/18-building-a-module.md`** — a design document, `status: proposed` |
| `opening`, twelfth | ADR 0100 |
The eleventh is this one. The test still calls it `daemon`, the code calls it `TypeProcess`, and
its paragraph is the only one that names a design document where the others name a decision.
Independently: in `declaration.go`, `TypeProcess` is the **only** shape in the vocabulary whose doc
comment cites no ADR — `network` cites 0029, `access` 0051, `opening` 0100, `user` and the refusal
of `action` cite 0005.
**So ADR 0029's mechanism worked exactly as designed and was not enough.** It requires every
addition to name something. It does not require that something to be a decision, and the one
addition that named a proposed design document instead is the one this issue is about.
### A correction to this trail, recorded because it was one grep from being a finding
The first search here was for `len(Vocabulary())` and found nothing, and the working conclusion for
two steps was that no count assertion existed any more — which would have been written up as "the
mechanism ADR 0029 relied on is gone." It is not gone. The test binds the slice to a local variable
first, so the assertion reads `len(speaks) != 12`. The claim was wrong, it was caught by reading the
file rather than by grepping it, and the shape of the error is the same one issue 113 recorded: a
negative search result read as a fact about the world.
## The argument the report asked for already exists, in a test comment
The report asked why a container rather than a supervised process, and said the reasoning was not
written down. It is — in `declaration_test.go`, as the eleventh shape's paragraph:
> Running code of one's own meant a `container` and therefore an image; running a script meant a
> `service` and a unit somebody else had to install. One intent — run this and keep it running —
> expressed two unrelated ways, with the hosting chosen before anything could be declared. […] It
> is a full-host shape rather than a portable one: it needs a process supervisor to install into.
> It does NOT need a container runtime, which is the point — only software that genuinely needs
> isolation asks for a container.
That is a decision's Context and Consequences, in a Go comment, in another repository. Nothing in
`02-DECISIONS/` contains it. `TypeProcess`'s own doc comment adds the rest — that three modes beat
three kinds, and that a first draft added a `daemon` for the long-running case alone.
## The catalogue is containers, and the one exception is the reference module
71 modules on `main`. Counting the `type` of every declared resource:
| `container` | `process` |
|---|---|
| 115 | **3** |
All three `process` resources are in **one** module: `showcase` — the module
[`20-writing-a-module.md`](../../03-DESIGN/01-to-be/20-writing-a-module.md) is a worked guide for.
### And in that module, the tools do not run
`showcase` declares its migrate, server and reporting steps as `process`. Its fourth resource, the
one for tools, is a **`container`** — and its image is the module's `helper` artifact, which the
same manifest declares as `kind: upstream` from a bare distribution base. Its command is
`sleep infinity`. It mounts the broker credential and sets the variable naming it, and runs nothing.
Meanwhile the module's `code` bundle declares six entrypoints. Three are run by the three `process`
resources. The tools entrypoint and the provisioner entrypoint are **run by no resource in the
manifest.**
Two consequences worth stating separately:
- **The worked guide does not match the module it documents.** The guide shows four `process`
resources, the fourth being `{"id": "tools", "type": "process"}`. The module has three and a
container.
- **This is the condition ADR 0047 was written to end, in a new shape.** That record's Context says
the conversion "produced tools and events that, as it stands, never execute," and its first
Consequence is that they become runnable. In the reference module they do not execute again —
not for want of a runtime this time, but because nothing declares one that runs them.
## The harness has no per-module boundary, and nothing refuses a second module
This is where ADR 0047's isolation argument is load-bearing, so it was checked rather than assumed.
- `mesh-sdk` `src/tools/index.ts`: `serveTools` iterates `collectTools()` over a module-level
registration array and serves **every registered module's** tools over the **one** `broker` it
was handed.
- `mesh-tools` `src/main.ts`: the modules to load come from one variable as a **comma-separated
list**, and the runtime sets its module and node identity from the **single** credential.
- `mesh-sdk` `src/events/index.ts`: an emitted event's `x-source` is stamped from that single
module identity.
Put together: load two modules into one runtime and everything the second emits is attributed to
the first, because there is one credential and the identity comes from it. That is precisely the
failure ADR 0047 predicted — "able to emit as any of them" — reached by a different route, since
the credential is correct and there is only one of it for two modules. **Nothing in either
repository refuses the second module**, and no test asserts that a runtime serves one.
### Ruled out, in fairness to the implementation
- **The serving key conforms.** ADR 0047 replaced a single `tools.invoke` dispatch with a per-tool
key, and the SDK does that: a tool is served on `<module>.<tool>` with the account scoped
`serve.<module>.*`. The superseded `tools.invoke` survives only in **prose** — the doc comment
directly above the conforming code, and the `mesh-tools` README, which also describes the runtime
as per-node. The code is ahead of its own documentation.
- **The credential shape conforms.** The sealed per-module credential file is preferred in code, and
the plain URL is documented as the bootstrap case before a module has an account — not the
ordinary path.
So the account is the right shape and the key is the right shape. It is the **process boundary**
that is declared nowhere and enforced by nothing.
## An unmerged report already asks the narrow version of this
Branch `issue/113-controller-container-or-process`, one commit, 2026-09-24, adds a report titled
**"Should the controller run as a container, or as a process the host supervises directly?"** with
`located-in: [mesh-controller module.json, mesh-host internal/apply]`. Its observation is that the
controller is declared a `container` with `network: host` — so container network isolation, the
property that resource type usually buys, is not in use — and it asks what `type: container` buys
that `type: process` would not.
It was unmerged and numbered 113, which is taken. A sibling branch,
`issue/113-record-the-repin-and-fold-114`, is why `114` was free.
**That report and this one are the instance and the general condition**, and they do not conflict:
it asks about one module that is not a code-carrying sidecar at all, and reaches the same question
from the opposite end. So it lands in this change as
[issue 114](../114-should-the-controller-be-a-container-or-a-process/00-report.md), its commit and
authorship intact, with a section pointing here — rather than being folded in and losing the
`network: host` observation, which is its own and is not reproduced above.
This diagnosis answers its first open question. The host's `process` shape does support what
[ADR 0005](../../02-DECISIONS/0005-the-node-host.md) describes for the host's own launcher — the
unit, the timer, restart, and run-to-completion gating are implemented and tested — so that report
does not need host-side work before it can be decided.
## What is located, and what is not
**Located — and it is not a code defect.** The implementation and the design layer agree with each
other; the **decision record is what is missing**, and the accepted record that occupies its place
says the other thing. ADR 0047 is `accepted`, cited by the module protocol, and unsuperseded, while
the host it describes has had a purpose-built shape for a module's own code since the eleventh
vocabulary entry.
| Owner | What is theirs |
|---|---|
| `hq` | the missing record for the `process` shape; ADR 0047 left standing; the worked guide that does not match the module |
| `mesh-catalog modules/showcase` | tools and provisioner entrypoints that no resource runs; a tools container that sleeps |
| `mesh-sdk src/tools/index.ts` | several modules served over one credential, unrefused and untested; a doc comment describing a superseded dispatch |
| `mesh-tools` | a README describing a per-node multi-module runtime the code no longer prefers |
**Not located, and deliberately open:** whether `process` or `container` is *right* for a module's
own code. This diagnosis establishes that the question was answered in practice and never recorded
— not which answer is correct. The arguments on both sides now exist in writing; they exist in a
test comment and a proposed design document, and one of them contradicts an accepted decision.
## What would close it
1. A decision record for the `process` shape, carrying the argument currently in
`declaration_test.go`, and saying what becomes of ADR 0047 — superseded in whole, or in the part
that names a container.
2. `18-building-a-module.md` and `20-writing-a-module.md` naming that record in `decisions:`, and
the worked manifest agreeing with the module.
3. The eleventh shape's paragraph in the vocabulary test naming a decision, like the other three.
4. **How the rule is checked, since a rule states how it is checked:** every shape in the host's
vocabulary names a decision, asserted where the count is already asserted — which turns "no
design without a decision" into something stronger than "no design without *a* decision" for
the one vocabulary where each entry is a security decision.
5. Whether a runtime may serve more than one module answered either way, and asserted — a refusal
if not, a test that two modules' events keep their own source if so.