novox/hq ADR 0141 and 04-ISSUES/142. A version was being delivered to a
machine and nothing started it: the launcher on these machines predates
the versions mechanism and runs the fixed binary path, so the delivery was
correct and inert.
Delivered as a FILE resource, not as part of an archive, and the
difference is the whole reason this is safe. A file is written atomically —
temp file in the same directory, then rename — so the running launcher
keeps the inode it was started from and the next start picks up the new
one. An archive writes in place with truncate, which would cut the file a
running shell is reading halfway through.
The manifest therefore carries a second copy of the script, and a test
refuses any difference between it and packaging/nox-mesh-host-launch.
Proven by drifting one and watching it fail. Two copies of a script is a
bad thing to accept, and the alternative was writing over a running
supervisor.
Together the two resources complete the loop: the version lands, the
running host stands aside because it sees one delivered, and the launcher
that starts next is the one that looks in versions/ and picks the newest
by arrival.
nox-mesh-host, not mesh-host. The command directory is cmd/mesh-host and
the launcher looks inside a delivered version for nox-mesh-host — the name
this is installed at and the name in its unit. The first delivery landed
the package's name, reported success, and would have been invisible.
novox/hq ADR 0141 and 04-ISSUES/142. The host half of the delivery has
been built and tested since 0141 and has never had a version to work on:
versions side by side, the newest runs, the running one stands aside
between reconciles, rollback picks a directory. This is the declaration
that gives it one.
One archive, unpacked to /usr/lib/nox-mesh-host/versions/${version}. The
version resolves to the artifact's digest, so an unchanged build lands at
the path it already had and re-composing a declaration moves nothing.
Not circular: the host applying this is a different version from the one
being written, and neither writes over the other — the kernel refuses to
truncate a running executable, which is the reason the path carries the
version rather than a link pointing at "current".
**The launcher is deliberately not delivered here.** The one on these
machines predates the versions mechanism and runs the fixed binary path,
so a delivered version is inert until it is replaced — and replacing it
from the mesh means writing over a running shell script, which sh reads
incrementally. That wants a designed swap rather than a file resource, and
it is the last piece rather than this one.
novox/hq 04-ISSUES/142 and ADR 0142. Nothing delivered the host because
nothing could compile it, and nothing could compile it partly because the
host was not a thing the mesh builds at all — it had no manifest.
One bundle in Go, for arch, built from cmd/mesh-host. A system is
required for a compiled artifact because a binary is pinned at link time
so a host refuses to touch a machine it was not built for (ADR 0005), and
`arch` is what all four of this mesh's machines report themselves to be.
Another system is another artifact and another build, which is what ADR
0142 means by one per target.
No resources yet. What places a version into a directory named for it
needs an archive resource whose path carries the version, and nothing
interpolates one — the second half of 0141's insight, and the next piece.
jschoubben