Extends the existing CheckIn RPC with a one-shot AgentCommand
(restart only -- stop/uninstall need real per-platform OS
service-manager integration and stay deliberately out of scope),
delivered at-most-once: cleared the instant it's handed to the agent
in a response, since a restarting agent's process is gone before it
could ever confirm receipt. On restart, the agent flushes whatever's
buffered, aborts its source task, and exits cleanly, relying entirely
on the host's own service manager to bring it back up.
Issuing a command is gated at RoleAdmin (stricter than config
editing's RoleEditor) and logged into the same audit_log table Phase
7's AI interactions use, via a new agent_command event type.
A real bug was found and fixed during live verification: the first
implementation tried to atomically read-and-clear pending_command in
a single INSERT...ON CONFLICT statement using a sibling CTE
referenced only from RETURNING, on the assumption that Postgres
evaluates every part of a WITH query against one pre-statement
snapshot. That's wrong specifically for FOR UPDATE, which always
reads the latest row version including one written earlier in the
same statement -- confirmed empirically (a restart command was
always coming back empty even when genuinely pending, so the agent
never received it). Fixed by splitting into two real, ordered
statements inside one explicit transaction.
See /docs/agent-management-design.md's "Lifecycle commands" section.
Extends the heartbeat mechanism with a second gRPC service on the same
mTLS channel (AgentControl.CheckIn, agent-initiated on the existing
heartbeat ticker -- still push-only, no inbound port on any agent) so
an agent reports its running config and can pick up an operator-set
override. A new web UI section (/agents) lists every agent that's
checked in, shows its reported config, and lets an operator edit a
narrow, deliberately-scoped subset remotely: batch/heartbeat tuning,
and (journald sources only) the unit filter.
TLS material and the ingest endpoint are never reportable or remotely
editable, by proto shape rather than a validation rule -- a bad or
malicious edit there could permanently strand an agent or redirect
where its logs go, unlike every other editable field, which only
degrades behavior.
An override lives only in the agent's memory (agent.toml is never
rewritten) and re-syncs on the agent's own schedule; changing the
journald filter aborts and respawns the source task since there's no
other way to change what's being tailed. Building the hot-reload path
surfaced a real, independent, pre-existing bug: shutdown was using
poll_timeout(), which only drains once flush_interval has elapsed,
silently dropping anything buffered more recently on every graceful
shutdown that landed between flushes -- fixed with a new unconditional
Batcher::flush_all(), now used at both shutdown and hot-reload.
Verified live end-to-end against a real stack: an edited heartbeat
interval changed a running agent's actual send cadence within one
check-in cycle (confirmed by the real timestamps landing in
ClickHouse), and an edited journald filter triggered a real source
restart, both reflected back in the next reported-config snapshot.
See /docs/agent-management-design.md.
jcoffey-dev