c1672218b1
systemd's default OOMPolicy=stop ends the whole unit when the kernel kills any process in it; set continue, as hive-subagent-daemon does. Module-eval case asserts it.
94 lines
3.9 KiB
Nix
94 lines
3.9 KiB
Nix
# `checks.module-eval-agent-memory` — see ./lib.nix for the shared
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# rationale (why this suite exists, naming convention, "evaluates
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# not executes").
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{
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pkgs,
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lib,
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self,
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nixosSystem,
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}:
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let
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inherit
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(import ./lib.nix {
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inherit
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pkgs
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lib
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self
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nixosSystem
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;
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})
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agent
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runGroup
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agentHarness
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;
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# The memory-pressure pair. `claudeMemoryMaxBytes` is the container's own
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# cap, rendered per agent by meta.rs — the capped arm is the one every
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# real deploy gets, the uncapped arm is a hive that set `infinity` or a
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# RAM percentage and so hands the module no byte count to size against.
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agentCapped = agent { claudeMemoryMaxBytes = 8589934592; };
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agentUncapped = agent { };
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agentBashDaemon = machine: machine.systemd.services.hive-bash-daemon;
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agentSubagentDaemon = machine: machine.systemd.services.hive-subagent-daemon;
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cases = [
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{
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# Two thirds of the container's cap, and a SOFT ceiling: the daemon's
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# cgroup holds every nested claude, so `MemoryHigh=` throttles the
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# subagent set as a whole before the kernel picks a victim, while the
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# absent `MemoryMax=` is what still lets one subagent use more than
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# its share on a container that has the memory free. A hard cap here
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# would trade the silent kill for a guaranteed wall, which is the
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# shape this deliberately does not have.
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name = "the subagent daemon throttles at two thirds of the container's memory";
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ok =
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let
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c = (agentSubagentDaemon agentCapped).serviceConfig;
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in
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c.MemoryHigh == "5726623061" && !(c ? MemoryMax);
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}
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{
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# What makes the case above able to fail. With no byte count for the
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# container there is no fraction to take, and a hardcoded fallback
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# would be a number about some other hive's machine — so the unit
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# renders no ceiling at all rather than a fabricated one.
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name = "an agent with no byte-valued memory cap renders no subagent ceiling";
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ok = !((agentSubagentDaemon agentUncapped).serviceConfig ? MemoryHigh);
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}
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{
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# The sign is the whole property, and it is easy to write backwards:
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# a HIGHER OOMScoreAdjust is a MORE likely victim. So the subagent
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# daemon must be strictly above zero and the harness strictly below
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# it — swap the two and the kernel takes the agent's own turn first,
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# which is worse than setting nothing at all. Both nested `claude`
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# processes inherit their unit's value, so ordering the units orders
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# the sessions. Held as an inequality rather than two constants: what
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# must not drift is the order, not the magnitudes.
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name = "the OOM killer prefers a subagent over the agent's own session";
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ok =
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let
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sub = (agentSubagentDaemon agentUncapped).serviceConfig.OOMScoreAdjust;
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own = (agentHarness agentUncapped).serviceConfig.OOMScoreAdjust;
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in
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sub > 0 && own < 0 && sub > own;
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}
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{
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# The pair the case above only makes sense with: preferring this unit
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# as the victim is an improvement only if losing one subagent isn't
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# losing all of them. systemd's default `stop` would take the daemon
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# and every sibling session down with whichever process the kernel
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# chose, which is the blast radius that made the preference a bad
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# trade in the first place.
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name = "one subagent losing the OOM draw does not stop the daemon";
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ok = (agentSubagentDaemon agentUncapped).serviceConfig.OOMPolicy == "continue";
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}
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{
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# Each bash task is a process in the daemon's cgroup; under `stop` one
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# OOM-killed task would end every running sibling task.
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name = "one bash task losing the OOM draw does not stop the daemon";
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ok = (agentBashDaemon agentUncapped).serviceConfig.OOMPolicy or null == "continue";
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}
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];
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in
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runGroup "agent-memory" cases
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