node-metrics

A small collector + TUI pair for watching Prometheus host metrics as a live terminal graph, over NATS JetStream.

Prometheus --poll--> collector --publish--> NATS JetStream <--read-only-- tui

• collector polls a Prometheus instance for each host in a scrape job, and publishes readings to a JetStream stream (history) and a KV bucket (latest value + host directory + live republish).
• tui never talks to Prometheus. It lists currently-reporting hosts from the KV, backfills a window of history from the stream, then switches to a live subscription. Hosts and metrics can be switched at runtime.

Adding a host requires no code change, just a Prometheus scrape config change. Adding a metric is one new entry in internal/registry.

Install

go install github.com/jw4/node-metrics/cmd/collector@latest
go install github.com/jw4/node-metrics/cmd/tui@latest

Or run the collector as a container: ghcr.io/jw4/node-metrics-collector.

Collector

Configured entirely by environment variables:

Variable	Default
NODE_METRICS_PROM_URL	http://kube-prometheus-stack-prometheus.monitoring.svc.cluster.local:9090
NODE_METRICS_NATS_URL	nats://nats.nats-prime.svc.cluster.local:4222
NODE_METRICS_NATS_CREDS	(required) path to a .creds file
NODE_METRICS_NATS_TLS_CA	(optional) path to a root CA cert
NODE_METRICS_JOB	node-exporter-external
NODE_METRICS_INTERVAL	60s
NODE_METRICS_MAX_AGE	168h (7d), JetStream stream retention
NODE_METRICS_MAX_BYTES	512MiB, JetStream stream size limit
NODE_METRICS_KV_TTL	5m
NODE_METRICS_HEALTHZ_ADDR	:8080, serves /healthz and /readyz

TUI

go install's binary is named tui (Go names it after the package directory, not the module):

tui -creds tui.creds -nats-url tls://nats.example.com:4222 -tls-ca ca.crt

Flag	Default	Meaning
-nats-url	nats://localhost:4222	NATS endpoint
-creds	(required)	path to a .creds file
-tls-ca	(empty)	root CA cert; required unless connecting in-cluster
-metric	cpu_temp	metric to display
-window	1h	backfill window on start / host switch
-log-file	(empty)	log connection/backfill errors here (bubbletea owns stderr)

Keys: tab/arrows switch hosts.

Requirements

A NATS server with JetStream enabled, and a stream + KV bucket the collector creates on first run. Both binaries connect with NKey/JWT credentials (.creds), set up an account and users however you manage NATS auth.

License

MIT, see LICENSE.