Feat: Refactor CPU usage metrics handling for platform-specific logic

Separated CPU usage metric calculations into platform-specific files to improve code organization. `cpu_other.go` handles non-Linux platforms while `cpu_linux.go` adds additional metrics and handles Linux-specific logic. Updated main statistics processing to use the new functions.

Signed-off-by: Christian Roessner <[email protected]>

server/stats/cpu_linux.go

@@ -0,0 +1,59 @@
+// Copyright (C) 2024 Christian Rößner
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+//go:build linux
+
+package stats
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var cpuNiceUsage = promauto.NewGauge(prometheus.GaugeOpts{
+	Name: "cpu_nice_usage_percent",
+	Help: "CPU nice usage in percent",
+})
+
+var cpuIowaitUsage = promauto.NewGauge(prometheus.GaugeOpts{
+	Name: "cpu_iowait_usage_percent",
+	Help: "CPU iowait usage in percent",
+})
+
+var cpuIRQUsage = promauto.NewGauge(prometheus.GaugeOpts{
+	Name: "cpu_irq_usage_percent",
+	Help: "CPU irq usage in percent",
+})
+
+var cpuSoftIRQUsage = promauto.NewGauge(prometheus.GaugeOpts{
+	Name: "cpu_softirq_usage_percent",
+	Help: "CPU softirq usage in percent",
+})
+
+var cpuStealUsage = promauto.NewGauge(prometheus.GaugeOpts{
+	Name: "cpu_steal_usage_percent",
+	Help: "CPU steal usage in percent",
+})
+
+func setNewStats(oldCpu, newCpu *cpu.Stats, total float64) {
+	cpuUserUsage.Set(float64(newCpu.User-oldCpu.User) / total * 100)
+	cpuSystemUsage.Set(float64(newCpu.System-oldCpu.System) / total * 100)
+	cpuIdleUsage.Set(float64(newCpu.Idle-oldCpu.Idle) / total * 100)
+
+	cpuIowaitUsage.Set(float64(newCpu.Iowait-oldCpu.Iowait) / total * 100)
+	cpuIRQUsage.Set(float64(newCpu.IRQ-oldCpu.IRQ) / total * 100)
+	cpuSoftIRQUsage.Set(float64(newCpu.SoftIRQ-oldCpu.SoftIRQ) / total * 100)
+	cpuStealUsage.Set(float64(newCpu.Steal-oldCpu.Steal) / total * 100)
+}

server/stats/cpu_other.go

@@ -0,0 +1,28 @@
+// Copyright (C) 2024 Christian Rößner
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+//go:build !linux
+
+package stats
+
+import (
+	"github.com/mackerelio/go-osstat/cpu"
+)
+
+func setNewStats(oldCpu, newCpu *cpu.Stats, total float64) {
+	cpuUserUsage.Set(float64(newCpu.User-oldCpu.User) / total * 100)
+	cpuSystemUsage.Set(float64(newCpu.System-oldCpu.System) / total * 100)
+	cpuIdleUsage.Set(float64(newCpu.Idle-oldCpu.Idle) / total * 100)
+}

server/stats/statistics.go

@@ -264,9 +264,7 @@ func MeasureCPU(ctx context.Context) {
 
 			total := float64(newCpu.Total - oldCpu.Total)
 
-			cpuUserUsage.Set(float64(newCpu.User-oldCpu.User) / total * 100)
-			cpuSystemUsage.Set(float64(newCpu.System-oldCpu.System) / total * 100)
-			cpuIdleUsage.Set(float64(newCpu.Idle-oldCpu.Idle) / total * 100)
+			setNewStats(&oldCpu, newCpu, total)
 
 			oldCpu = *newCpu
 		}