unmarshal camelcase matchLabels and matchExpressions in target allocator config

Author: davidhaja

.chloggen/3350-ta-matchlabels.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. collector, target allocator, auto-instrumentation, opamp, github action)
+component: target allocator
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Support camelcase matchLabels and matchExpressions in target allocator config"
+
+# One or more tracking issues related to the change
+issues: [3350]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

cmd/otel-allocator/config/config.go

@@ -21,14 +21,16 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"strings"
 	"time"
 
+	"dario.cat/mergo"
 	"github.com/go-logr/logr"
+	yaml "github.com/goccy/go-yaml"
 	"github.com/prometheus/common/model"
 	promconfig "github.com/prometheus/prometheus/config"
 	_ "github.com/prometheus/prometheus/discovery/install"
 	"github.com/spf13/pflag"
-	"gopkg.in/yaml.v2"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
@@ -75,6 +77,11 @@ type HTTPSServerConfig struct {
 	TLSKeyFilePath  string `yaml:"tls_key_file_path,omitempty"`
 }
 
+type LabeLSelectorPaths struct {
+	MatchLabelsPath      string
+	MatchExpressionsPath string
+}
+
 func LoadFromFile(file string, target *Config) error {
 	return unmarshal(target, file)
 }
@@ -148,14 +155,113 @@ func LoadFromCLI(target *Config, flagSet *pflag.FlagSet) error {
 	return nil
 }
 
+// Extract value from specific YAMLPath
+func readPath(p string, yamlFile []byte, f interface{}) error {
+	path, err := yaml.PathString(p)
+	if err != nil {
+		return err
+	}
+	if err := path.Read(strings.NewReader(string(yamlFile)), f); err != nil {
+		return err
+	}
+	return nil
+}
+
+func readLabelSelectorPaths(ps LabeLSelectorPaths, yamlFile []byte, f *metav1.LabelSelector) (bool, error) {
+	founderrs := 0
+
+	if err := readPath(ps.MatchLabelsPath, yamlFile, &f.MatchLabels); err != nil {
+		if !errors.Is(err, yaml.ErrNotFoundNode) {
+			return false, err
+		}
+		founderrs += 1
+	}
+	if err := readPath(ps.MatchExpressionsPath, yamlFile, &f.MatchExpressions); err != nil {
+		if !errors.Is(err, yaml.ErrNotFoundNode) {
+			return false, err
+		}
+		founderrs += 1
+	}
+
+	return founderrs < 2, nil
+}
+
+func flexibleLabelSelector(yamlFile []byte, fieldPathsMap map[*metav1.LabelSelector]LabeLSelectorPaths) error {
+	for f, ps := range fieldPathsMap {
+		tmpls := metav1.LabelSelector{}
+
+		found, err := readLabelSelectorPaths(ps, yamlFile, &tmpls)
+		if err != nil {
+			return err
+		}
+
+		if found {
+			if err := mergo.Merge(f, tmpls, mergo.WithOverride); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func flexibleCollectorSelector(yamlFile []byte, cfg *Config) error {
+	collectorSelectorFieldPathsMap := map[*metav1.LabelSelector]LabeLSelectorPaths{
+		cfg.CollectorSelector: {
+			MatchLabelsPath:      "$.collector_selector.matchlabels",
+			MatchExpressionsPath: "$.collector_selector.matchexpressions",
+		},
+	}
+
+	if err := flexibleLabelSelector(yamlFile, collectorSelectorFieldPathsMap); err != nil {
+		return err
+	}
+	return nil
+}
+
+func flexiblePrometheusCR(yamlFile []byte, cfg *Config) error {
+	prometheusCRFieldPathsMap := map[*metav1.LabelSelector]LabeLSelectorPaths{
+		cfg.PrometheusCR.PodMonitorSelector: {
+			MatchLabelsPath:      "$.prometheus_cr.pod_monitor_selector.matchlabels",
+			MatchExpressionsPath: "$.prometheus_cr.pod_monitor_selector.matchexpressions",
+		},
+		cfg.PrometheusCR.ServiceMonitorSelector: {
+			MatchLabelsPath:      "$.prometheus_cr.service_monitor_selector.matchlabels",
+			MatchExpressionsPath: "$.prometheus_cr.service_monitor_selector.matchexpressions",
+		},
+		cfg.PrometheusCR.ServiceMonitorNamespaceSelector: {
+			MatchLabelsPath:      "$.prometheus_cr.service_monitor_namespace_selector.matchlabels",
+			MatchExpressionsPath: "$.prometheus_cr.service_monitor_namespace_selector.matchexpressions",
+		},
+		cfg.PrometheusCR.PodMonitorNamespaceSelector: {
+			MatchLabelsPath:      "$.prometheus_cr.pod_monitor_namespace_selector.matchlabels",
+			MatchExpressionsPath: "$.prometheus_cr.pod_monitor_namespace_selector.matchexpressions",
+		},
+	}
+
+	if err := flexibleLabelSelector(yamlFile, prometheusCRFieldPathsMap); err != nil {
+		return err
+	}
+	return nil
+}
+
 func unmarshal(cfg *Config, configFile string) error {
 	yamlFile, err := os.ReadFile(configFile)
 	if err != nil {
 		return err
 	}
+
 	if err = yaml.Unmarshal(yamlFile, cfg); err != nil {
 		return fmt.Errorf("error unmarshaling YAML: %w", err)
 	}
+
+	if err := flexibleCollectorSelector(yamlFile, cfg); err != nil {
+		return err
+	}
+
+	if err := flexiblePrometheusCR(yamlFile, cfg); err != nil {
+		return err
+	}
+
 	return nil
 }