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

internal/metricAggregator/metricAggregator.go

@@ -10,6 +10,7 @@ package metricAggregator
 import (
 	"context"
 	"fmt"
+	"maps"
 	"math"
 	"os"
 	"strings"
@@ -121,9 +122,7 @@ func (c *metricAggregator) Init(output chan lp.CCMessage) error {
 
 func (c *metricAggregator) Eval(starttime time.Time, endtime time.Time, metrics []lp.CCMessage) {
 	vars := make(map[string]interface{})
-	for k, v := range c.constants {
-		vars[k] = v
-	}
+	maps.Copy(vars, c.constants)
 	vars["starttime"] = starttime
 	vars["endtime"] = endtime
 	for _, f := range c.functions {

internal/metricAggregator/metricAggregatorFunctions.go

@@ -11,10 +11,9 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
+	"slices"
 	"strings"
 
-	"golang.org/x/exp/slices"
-
 	topo "github.com/ClusterCockpit/cc-metric-collector/pkg/ccTopology"
 )
 
@@ -169,7 +168,7 @@ func medianfunc(args interface{}) (interface{}, error) {
 
 func lenfunc(args interface{}) (interface{}, error) {
 	var err error = nil
-	var length int = 0
+	length := 0
 	switch values := args.(type) {
 	case []float64:
 		length = len(values)
@@ -238,7 +237,7 @@ func matchfunc(args ...interface{}) (interface{}, error) {
 	case string:
 		switch total := args[1].(type) {
 		case string:
-			smatch := strings.Replace(match, "%", "\\", -1)
+			smatch := strings.ReplaceAll(match, "%", "\\")
 			regex, err := regexp.Compile(smatch)
 			if err != nil {
 				return false, err

internal/metricRouter/metricCache.go

@@ -51,7 +51,7 @@ type MetricCache interface {
 }
 
 func (c *metricCache) Init(output chan lp.CCMessage, ticker mct.MultiChanTicker, wg *sync.WaitGroup, numPeriods int) error {
-	var err error = nil
+	var err error
 	c.done = make(chan bool)
 	c.wg = wg
 	c.ticker = ticker
@@ -161,8 +161,8 @@ func (c *metricCache) DeleteAggregation(name string) error {
 // is the current one, index=1 the last interval and so on. Returns and empty array if a wrong index
 // is given (negative index, index larger than configured number of total intervals, ...)
 func (c *metricCache) GetPeriod(index int) (time.Time, time.Time, []lp.CCMessage) {
-	var start time.Time = time.Now()
-	var stop time.Time = time.Now()
+	start := time.Now()
+	stop := time.Now()
 	var metrics []lp.CCMessage
 	if index >= 0 && index < c.numPeriods {
 		pindex := c.curPeriod - index

internal/metricRouter/metricRouter.go

@@ -107,10 +107,8 @@ func (r *metricRouter) Init(ticker mct.MultiChanTicker, wg *sync.WaitGroup, rout
 		cclog.ComponentError("MetricRouter", err.Error())
 		return err
 	}
-	r.maxForward = 1
-	if r.config.MaxForward > r.maxForward {
-		r.maxForward = r.config.MaxForward
-	}
+	r.maxForward = max(1, r.config.MaxForward)
+
 	if r.config.NumCacheIntervals > 0 {
 		r.cache, err = NewCache(r.cache_input, r.ticker, &r.cachewg, r.config.NumCacheIntervals)
 		if err != nil {
@@ -118,50 +116,74 @@ func (r *metricRouter) Init(ticker mct.MultiChanTicker, wg *sync.WaitGroup, rout
 			return err
 		}
 		for _, agg := range r.config.IntervalAgg {
-			r.cache.AddAggregation(agg.Name, agg.Function, agg.Condition, agg.Tags, agg.Meta)
+			err = r.cache.AddAggregation(agg.Name, agg.Function, agg.Condition, agg.Tags, agg.Meta)
+			if err != nil {
+				return fmt.Errorf("MetricCache AddAggregation() failed: %w", err)
+			}
 		}
 	}
 	p, err := mp.NewMessageProcessor()
 	if err != nil {
-		return fmt.Errorf("initialization of message processor failed: %v", err.Error())
+		return fmt.Errorf("MessageProcessor NewMessageProcessor() failed: %w", err)
 	}
 	r.mp = p
 
 	if len(r.config.MessageProcessor) > 0 {
 		err = r.mp.FromConfigJSON(r.config.MessageProcessor)
 		if err != nil {
-			return fmt.Errorf("failed parsing JSON for message processor: %v", err.Error())
+			return fmt.Errorf("MessageProcessor FromConfigJSON() failed: %w", err)
 		}
 	}
 	for _, mname := range r.config.DropMetrics {
-		r.mp.AddDropMessagesByName(mname)
+		err = r.mp.AddDropMessagesByName(mname)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddDropMessagesByName() failed: %w", err)
+		}
 	}
 	for _, cond := range r.config.DropMetricsIf {
-		r.mp.AddDropMessagesByCondition(cond)
+		err = r.mp.AddDropMessagesByCondition(cond)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddDropMessagesByCondition() failed: %w", err)
+		}
 	}
 	for _, data := range r.config.AddTags {
 		cond := data.Condition
 		if cond == "*" {
 			cond = "true"
 		}
-		r.mp.AddAddTagsByCondition(cond, data.Key, data.Value)
+		err = r.mp.AddAddTagsByCondition(cond, data.Key, data.Value)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddAddTagsByCondition() failed: %w", err)
+		}
 	}
 	for _, data := range r.config.DelTags {
 		cond := data.Condition
 		if cond == "*" {
 			cond = "true"
 		}
-		r.mp.AddDeleteTagsByCondition(cond, data.Key, data.Value)
+		err = r.mp.AddDeleteTagsByCondition(cond, data.Key, data.Value)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddDeleteTagsByCondition() failed: %w", err)
+		}
 	}
 	for oldname, newname := range r.config.RenameMetrics {
-		r.mp.AddRenameMetricByName(oldname, newname)
+		err = r.mp.AddRenameMetricByName(oldname, newname)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddRenameMetricByName() failed: %w", err)
+		}
 	}
 	for metricName, prefix := range r.config.ChangeUnitPrefix {
-		r.mp.AddChangeUnitPrefix(fmt.Sprintf("name == '%s'", metricName), prefix)
+		err = r.mp.AddChangeUnitPrefix(fmt.Sprintf("name == '%s'", metricName), prefix)
+		if err != nil {
+			return fmt.Errorf("MessageProcessor AddChangeUnitPrefix() failed: %w", err)
+		}
 	}
 	r.mp.SetNormalizeUnits(r.config.NormalizeUnits)
 
-	r.mp.AddAddTagsByCondition("true", r.config.HostnameTagName, r.hostname)
+	err = r.mp.AddAddTagsByCondition("true", r.config.HostnameTagName, r.hostname)
+	if err != nil {
+		return fmt.Errorf("MessageProcessor AddAddTagsByCondition() failed: %w", err)
+	}
 
 	// r.config.dropMetrics = make(map[string]bool)
 	// for _, mname := range r.config.DropMetrics {