Golangci lint fixes (#195)

* Add golangci-lin as make target
* Fix: could omit type ... from declaration; it will be inferred from the right-hand side (staticcheck)
* Fix func intArrayContains is unused (unused)
* Fix: could use strings.ReplaceAll instead (staticcheck)
* Fix: could expand call to math.Pow (staticcheck)
* Fix: could use tagged switch on `...` (staticcheck)
* Fix: Error return value of `...` is not checked (errcheck)
* Fix: ineffectual assignment to err (ineffassign)
* Fix: There is no need to wait for command completion
* Add cpustat, diskstat and schedstat config
* Use slices to exclude metrics
* Replaced stringArrayContains by slices.Contains
* Replace m[k]=v loop with maps.Copy
* Use module slices from the standard library. Remove use of golang.org/x/exp/slices
* Use SplitSeq and max to modernize code

collectors/schedstatMetric.go

@@ -11,7 +11,6 @@ import (
 	"bufio"
 	"encoding/json"
 	"fmt"
-	"math"
 	"os"
 	"strconv"
 	"strings"
@@ -47,37 +46,37 @@ type SchedstatCollector struct {
 // Called once by the collector manager
 // All tags, meta data tags and metrics that do not change over the runtime should be set here
 func (m *SchedstatCollector) Init(config json.RawMessage) error {
-	var err error = nil
 	// Always set the name early in Init() to use it in cclog.Component* functions
 	m.name = "SchedstatCollector"
 	// This is for later use, also call it early
-	m.setup()
+	if err := m.setup(); err != nil {
+		return fmt.Errorf("%s Init(): setup() call failed: %w", m.name, err)
+	}
 	// Tell whether the collector should be run in parallel with others (reading files, ...)
 	// or it should be run serially, mostly for collectors acutally doing measurements
 	// because they should not measure the execution of the other collectors
 	m.parallel = true
 	// Define meta information sent with each metric
 	// (Can also be dynamic or this is the basic set with extension through AddMeta())
-	m.meta = map[string]string{"source": m.name, "group": "SCHEDSTAT"}
+	m.meta = map[string]string{
+		"source": m.name,
+		"group":  "SCHEDSTAT",
+	}
 
 	// Read in the JSON configuration
 	if len(config) > 0 {
-		err = json.Unmarshal(config, &m.config)
-		if err != nil {
-			cclog.ComponentError(m.name, "Error reading config:", err.Error())
-			return err
+		if err := json.Unmarshal(config, &m.config); err != nil {
+			return fmt.Errorf("%s Init(): Error reading config: %w", m.name, err)
 		}
 	}
 
 	// Check input file
-	file, err := os.Open(string(SCHEDSTATFILE))
+	file, err := os.Open(SCHEDSTATFILE)
 	if err != nil {
-		cclog.ComponentError(m.name, err.Error())
+		return fmt.Errorf("%s Init(): Failed opening scheduler statistics file \"%s\": %w", m.name, SCHEDSTATFILE, err)
 	}
-	defer file.Close()
 
 	// Pre-generate tags for all CPUs
-	num_cpus := 0
 	m.cputags = make(map[string]map[string]string)
 	m.olddata = make(map[string]map[string]int64)
 	scanner := bufio.NewScanner(file)
@@ -89,11 +88,19 @@ func (m *SchedstatCollector) Init(config json.RawMessage) error {
 			cpu, _ := strconv.Atoi(cpustr)
 			running, _ := strconv.ParseInt(linefields[7], 10, 64)
 			waiting, _ := strconv.ParseInt(linefields[8], 10, 64)
-			m.cputags[linefields[0]] = map[string]string{"type": "hwthread", "type-id": fmt.Sprintf("%d", cpu)}
-			m.olddata[linefields[0]] = map[string]int64{"running": running, "waiting": waiting}
-			num_cpus++
+			m.cputags[linefields[0]] = map[string]string{
+				"type":    "hwthread",
+				"type-id": fmt.Sprintf("%d", cpu),
+			}
+			m.olddata[linefields[0]] = map[string]int64{
+				"running": running,
+				"waiting": waiting,
+			}
 		}
 	}
+	if err := file.Close(); err != nil {
+		return fmt.Errorf("%s Init(): Failed closing scheduler statistics file \"%s\": %w", m.name, SCHEDSTATFILE, err)
+	}
 
 	// Save current timestamp
 	m.lastTimestamp = time.Now()
@@ -109,8 +116,8 @@ func (m *SchedstatCollector) ParseProcLine(linefields []string, tags map[string]
 	diff_running := running - m.olddata[linefields[0]]["running"]
 	diff_waiting := waiting - m.olddata[linefields[0]]["waiting"]
 
-	var l_running float64 = float64(diff_running) / tsdelta.Seconds() / (math.Pow(1000, 3))
-	var l_waiting float64 = float64(diff_waiting) / tsdelta.Seconds() / (math.Pow(1000, 3))
+	l_running := float64(diff_running) / tsdelta.Seconds() / 1000_000_000
+	l_waiting := float64(diff_waiting) / tsdelta.Seconds() / 1000_000_000
 
 	m.olddata[linefields[0]]["running"] = running
 	m.olddata[linefields[0]]["waiting"] = waiting
@@ -134,11 +141,19 @@ func (m *SchedstatCollector) Read(interval time.Duration, output chan lp.CCMessa
 	now := time.Now()
 	tsdelta := now.Sub(m.lastTimestamp)
 
-	file, err := os.Open(string(SCHEDSTATFILE))
+	file, err := os.Open(SCHEDSTATFILE)
 	if err != nil {
-		cclog.ComponentError(m.name, err.Error())
+		cclog.ComponentError(
+			m.name,
+			fmt.Sprintf("Read(): Failed to open file '%s': %v", SCHEDSTATFILE, err))
 	}
-	defer file.Close()
+	defer func() {
+		if err := file.Close(); err != nil {
+			cclog.ComponentError(
+				m.name,
+				fmt.Sprintf("Read(): Failed to close file '%s': %v", SCHEDSTATFILE, err))
+		}
+	}()
 
 	scanner := bufio.NewScanner(file)
 	for scanner.Scan() {