Jochen: "I thought we did not want to run the host under a systemd/openrc/init
loop, but instead had our own host-init program?" -- and that was right. I had
moved the give-up logic out of unit files and left RESTART in them, with the
launcher exec'ing the host and disappearing. So init still decided when the
host came back, which is the arrangement 0061 exists to remove.
The launcher now stays and supervises: starts the host as a child, waits,
decides. Init is asked for one thing, run this at boot. There is an OpenRC
script beside the systemd unit now, four lines each, which is the point --
a second init is transcription rather than a port.
The cost of not exec'ing is signals. A supervisor that exits while its child
runs leaves the host to be killed rather than to stop, and an apply interrupted
that way is the half-configured machine this project is about. So SIGTERM is
trapped, passed down, and waited on.
Two bugs, both found by the tests rather than by review:
A clean exit was counted as a failure. The host exits cleanly to stand aside
for a new binary after an upgrade (0057), so a host that upgraded itself three
times rolled itself back having worked perfectly every time. The counter now
counts CONSECUTIVE FAILURES, incremented after the wait rather than before the
start.
And when rolling back I reset the counter file but not the variable, so the
next failure counted from the old value -- the rolled-back version got one
attempt instead of three.
Also: the host now clears the counter when it completes a reconcile, at the
same moment it records known-good and for the same reason. Without it the count
only climbs, and a node up for months rolls itself back on its third ordinary
restart -- a healthy machine undone by its own recovery.
One test expectation was tightened rather than fixed: "resets the counter after
rolling back" asserted exactly 0, which was true only under the old
count-before-start semantics. It now asserts the property -- below the limit --
since 1 is correct after a rollback plus one failure.
32 launcher tests, all confirmed to bite.
ADR 0061. Recovery was the most systemd-specific part of the host, and it is
the part that must work on a machine where nothing else does -- which made
unit-file syntax a poor place for it, because syntax cannot be tested and the
one time it runs is the one time nobody can afford it wrong.
So StartLimitBurst and OnFailure move into a launcher script that init starts
instead of the host. The unit drops to start-at-boot and restart-on-exit, which
OpenRC, runit, s6 and an Android init.rc can all express. Everything 0059
decided is kept: two watchdogs, roll back once, recovery is local, the rollback
shares no code with the host.
The counter is the whole mechanism, so it is what the tests are mostly about.
Three real problems came out of writing them:
A counter file holding "1 2" became "12" -- `tr -d [:space:]` concatenates
rather than rejecting -- which is past the limit, so a HEALTHY node rolled
itself back. Now it reads the first field and insists on a plain integer.
The corrupt-counter test used "not-a-number", which shell arithmetic happens to
evaluate to 0, so it passed with the guard removed and proved nothing. Replaced
with values that discriminate: "5x" errors under set -e and kills the launcher,
and "0x10" is read as HEX 16 -- past the limit, so again a healthy node rolls
back.
And the test harness itself was wrong. With `set -e` and a bare launcher call,
removing a guard killed the script at the first corrupt case and silently
skipped everything after -- reporting a full pass over tests that never ran.
Every launcher call now records its failure instead of aborting. Same class as
the placebo assertion found last time, and the reason to keep injecting faults
rather than trusting green.
Both scripts run in `make check`. 27 launcher tests, 9 rollback tests, all
confirmed to bite.
jschoubben