From dd52c89918be7ae6f344229a024d38f844607ab4 Mon Sep 17 00:00:00 2001
From: Dan Fuhry <dan@fuhry.com>
Date: Tue, 16 Jan 2024 23:21:55 -0500
Subject: [PATCH] apcups_exporter: handle apcupsd restarts/downtime; add
 systemd unit

---
 go.mod                                        |  1 +
 go.sum                                        |  2 ++
 metrics/apcups_exporter/main.go               | 36 +++++++++++++++----
 .../systemd/apcupsd-exporter.service          | 11 ++++++
 4 files changed, 44 insertions(+), 6 deletions(-)
 create mode 100644 metrics/apcups_exporter/systemd/apcupsd-exporter.service

diff --git a/go.mod b/go.mod
index ad4233c..13a3f50 100644
--- a/go.mod
+++ b/go.mod
@@ -43,6 +43,7 @@ require (
 	github.com/BurntSushi/toml v1.2.1 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
 	github.com/denverdino/aliyungo v0.0.0-20190125010748-a747050bb1ba // indirect
 	github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c // indirect
diff --git a/go.sum b/go.sum
index c156bf5..434c6da 100644
--- a/go.sum
+++ b/go.sum
@@ -98,6 +98,8 @@ github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3Ee
 github.com/coreos/go-systemd v0.0.0-20180511133405-39ca1b05acc7/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20190620071333-e64a0ec8b42a/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
+github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf h1:iW4rZ826su+pqaw19uhpSCzhj44qo35pNgKFGqzDKkU=
+github.com/coreos/go-systemd v0.0.0-20191104093116-d3cd4ed1dbcf/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/coreos/go-systemd/v22 v22.4.0 h1:y9YHcjnjynCd/DVbg5j9L/33jQM3MxJlbj/zWskzfGU=
 github.com/coreos/go-systemd/v22 v22.4.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
diff --git a/metrics/apcups_exporter/main.go b/metrics/apcups_exporter/main.go
index 0fa6b6e..d4ccbd9 100644
--- a/metrics/apcups_exporter/main.go
+++ b/metrics/apcups_exporter/main.go
@@ -4,10 +4,13 @@ import (
 	"context"
 	"flag"
 	"os/signal"
+	"sync"
 	"syscall"
 	"time"
 
+	"github.com/coreos/go-systemd/daemon"
 	"github.com/mdlayher/apcupsd"
+
 	"go.fuhry.dev/runtime/metrics/metricbus/mbclient"
 	"go.fuhry.dev/runtime/utils/log"
 )
@@ -19,16 +22,20 @@ type apcMetrics struct {
 }
 
 func main() {
+	var apcConn *apcupsd.Client
+	var err error
+	var sdNotifyOnce sync.Once
+
 	ctx, _ := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	flag.Parse()
 
 	svc := mbclient.NewService(ctx)
 
-	apcupsd, err := apcupsd.Dial("tcp", "127.0.0.1:3551")
-	if err != nil {
-		log.Panic(err)
-	}
-	defer apcupsd.Close()
+	defer (func() {
+		if apcConn != nil {
+			apcConn.Close()
+		}
+	})()
 
 	metrics := apcMetrics{
 		lineVoltage:      svc.DefineGauge("apcups_line_voltage", "AC mains line voltage"),
@@ -48,13 +55,30 @@ func main() {
 	for {
 		select {
 		case <-ticker.C:
-			status, err := apcupsd.Status()
+			if apcConn == nil {
+				apcConn, err = apcupsd.Dial("tcp", "127.0.0.1:3551")
+				if err != nil {
+					log.Default().Errorf("error getting status from apcupsd: %v", err)
+					continue
+				}
+			}
+			status, err := apcConn.Status()
 			if err != nil {
 				log.Default().Errorf("error getting status from apcupsd: %v", err)
+				apcConn.Close()
+
+				apcConn = nil
 				continue
 			}
 			log.Default().V(1).Infof("UPS status: state=%s, line voltage: %.1f, load %% %.1f, seconds left %.0f, charge pct %.1f",
 				status.Status, status.LineVoltage, status.LoadPercent, status.TimeLeft.Seconds(), status.BatteryChargePercent)
+			if status.LoadPercent == 0.0 && status.BatteryChargePercent == 0.0 {
+				log.Default().V(1).Error("refusing to log impossible apcups state")
+				continue
+			}
+			sdNotifyOnce.Do(func() {
+				daemon.SdNotify(false, daemon.SdNotifyReady)
+			})
 			metrics.lineVoltage.Set(status.LineVoltage)
 			metrics.loadPercentage.Set(status.LoadPercent)
 			metrics.secondsLeft.Set(status.TimeLeft.Seconds())
diff --git a/metrics/apcups_exporter/systemd/apcupsd-exporter.service b/metrics/apcups_exporter/systemd/apcupsd-exporter.service
new file mode 100644
index 0000000..b815ead
--- /dev/null
+++ b/metrics/apcups_exporter/systemd/apcupsd-exporter.service
@@ -0,0 +1,11 @@
+[Unit]
+Description=Export stats from apcupsd via metric-collector
+Requires=apcupsd.service
+
+[Service]
+Type=notify
+User=daemon
+ExecStart=/usr/bin/apcupsd-exporter
+
+[Install]
+WantedBy=default.target
-- 
2.50.1