host-metrics: operator README

stack_orchestrator/data/stacks/host-metrics/README.md

@@ -7,6 +7,115 @@ it runs on. Writes to an InfluxDB 1.x endpoint of your choosing.
 
 Deploy one instance per machine you want monitored.
 
-## Quick deploy
+## What gets collected
 
-(Filled in by a later task.)
+| Input | Measurements (in InfluxDB) |
+|-------|----------------------------|
+| inputs.cpu (totalcpu only) | cpu (`cpu=cpu-total`) |
+| inputs.mem | mem |
+| inputs.swap | swap |
+| inputs.system | system (uptime, load1/5/15, n_users, n_cpus) |
+| inputs.processes | processes (running/sleeping/blocked/zombies) |
+| inputs.disk | disk (used/free/used_percent per mount) |
+| inputs.diskio | diskio (read/write bytes/ops per device) |
+| inputs.net | net (bytes/packets/err in/out per interface) |
+| inputs.zfs (opt-in via COLLECT_ZFS=true) | zfs (ARC stats, pool state) |
+
+All rows are tagged with `host` (kernel hostname, or `HOST_TAG` override).
+
+## Deploy
+
+### Create a spec
+
+```bash
+laconic-so --stack <path>/stack_orchestrator/data/stacks/host-metrics \
+    deploy init --output spec-host-metrics.yml
+```
+
+Edit `spec-host-metrics.yml` to look like:
+
+```yaml
+stack: <path>/stack_orchestrator/data/stacks/host-metrics
+deploy-to: compose
+credentials-files:
+  - ~/.credentials/host-metrics.env
+config:
+  INFLUXDB_URL: 'https://influxdb.example.com'
+  INFLUXDB_DB: 'host_metrics'          # default; override for a custom DB
+  HOST_TAG: 'validator-1'              # optional; defaults to kernel hostname
+  COLLECT_INTERVAL: '10s'              # telegraf collection + flush cadence
+  COLLECT_ZFS: 'false'                 # set to 'true' on ZFS hosts
+```
+
+`~/.credentials/host-metrics.env` must contain:
+
+```
+INFLUXDB_WRITE_USER=<writer-username>
+INFLUXDB_WRITE_PASSWORD=<writer-password>
+```
+
+These are issued by the InfluxDB admin (the monitoring host operator); they
+are the same writer-only credentials used by validators/RPCs to push agave
+metrics.
+
+### Create and start
+
+```bash
+laconic-so deployment create --spec-file spec-host-metrics.yml --deployment-dir ./deployment-host-metrics
+laconic-so deployment --dir ./deployment-host-metrics start
+```
+
+### Verify
+
+```bash
+docker logs $(docker ps -qf name=host-metrics) | head
+```
+
+Expected: telegraf prints its startup banner and `Loaded inputs: ...`. No
+errors about missing config or auth failures.
+
+Within ~20 seconds, the host's data appears in the InfluxDB endpoint's
+`host_metrics` database (or whichever DB you set in INFLUXDB_DB) and in
+any Grafana dashboards bound to that DB.
+
+## Configuration reference
+
+| Env | Required | Default | Notes |
+|-----|----------|---------|-------|
+| `INFLUXDB_URL` | yes | - | Full URL including scheme. Example: `https://influxdb.example.com`. |
+| `INFLUXDB_DB` | no | `host_metrics` | Target database. Must exist (writer is not granted CREATE). |
+| `INFLUXDB_WRITE_USER` | yes | - | Writer-only user. |
+| `INFLUXDB_WRITE_PASSWORD` | yes | - | Writer-only password. |
+| `COLLECT_INTERVAL` | no | `10s` | Telegraf collection and flush cadence. |
+| `HOST_TAG` | no | empty | Overrides the kernel hostname for the `host` tag on every row. Useful when a VM has a generic hostname. |
+| `COLLECT_ZFS` | no | `false` | Set to `true` to enable `inputs.zfs` (pool state + ARC stats). |
+
+## ZFS hosts
+
+`inputs.disk` already reports used/free per mount for any filesystem type
+including ZFS, so the disk-usage view works out of the box. Setting
+`COLLECT_ZFS=true` additionally enables `inputs.zfs` which reads
+`/proc/spl/kstat/zfs/...` and emits ARC hit ratio, ARC size, and per-pool
+health metrics. The bind mount of `/proc` provides the necessary
+visibility; no extra mounts are needed.
+
+If you set `COLLECT_ZFS=true` on a non-ZFS host, telegraf logs an error
+once per collection cycle and skips the input. Harmless but noisy; leave
+the toggle off on non-ZFS machines.
+
+## Troubleshooting
+
+| Symptom | Likely cause |
+|---------|-------------|
+| Container fails to start with `FATAL: INFLUXDB_URL is required but empty` | Missing required env. Check spec.yml + credentials file. |
+| Container starts, no rows appear in InfluxDB | Writer credentials wrong, or InfluxDB unreachable from this host's network. Check `docker logs <telegraf>` for `Post ... 401` / `connection refused`. |
+| Two hosts overwriting each other's series | Both use the same kernel hostname. Set distinct `HOST_TAG` values. |
+| `inputs.processes` reports only 1 process | `pid: host` missing from compose. Re-deploy. |
+
+## Caveats
+
+- Requires Docker with privileges to bind-mount `/`, `/proc`, `/sys`, and to
+  share the host PID namespace. Rootless Docker installations may refuse
+  `pid: host` and the `/` bind mount.
+- One deployment per host. Running two on the same machine writes
+  duplicate rows under the same `host` tag.