func AppendMetricRelabelConfig()

in otelcollector/shared/configmap/mp/prometheus-config-merger.go [137:205]
52 lines of code
12 McCabe index (conditional complexity)

func AppendMetricRelabelConfig(yamlConfigFile, keepListRegex string) error {
	fmt.Printf("Starting to append keep list regex or minimal ingestion regex to %s\n", yamlConfigFile)

	content, err := os.ReadFile(yamlConfigFile)
	if err != nil {
		return fmt.Errorf("error reading config file %s: %v. The keep list regex will not be used", yamlConfigFile, err)
	}

	var config map[string]interface{}
	if err := yaml.Unmarshal(content, &config); err != nil {
		return fmt.Errorf("error unmarshalling YAML for %s: %v. The keep list regex will not be used", yamlConfigFile, err)
	}

	keepListMetricRelabelConfig := map[string]interface{}{
		"source_labels": []interface{}{"__name__"},
		"action":        "keep",
		"regex":         keepListRegex,
	}

	if scrapeConfigs, ok := config["scrape_configs"].([]interface{}); ok {
		for i, scfg := range scrapeConfigs {
			// Ensure scfg is a map with string keys
			if scfgMap, ok := scfg.(map[interface{}]interface{}); ok {
				// Convert to map[string]interface{}
				stringScfgMap := make(map[string]interface{})
				for k, v := range scfgMap {
					if key, ok := k.(string); ok {
						stringScfgMap[key] = v
					} else {
						return fmt.Errorf("encountered non-string key in scrape config map: %v", k)
					}
				}

				// Update or add metric_relabel_configs
				if metricRelabelCfgs, ok := stringScfgMap["metric_relabel_configs"].([]interface{}); ok {
					stringScfgMap["metric_relabel_configs"] = append(metricRelabelCfgs, keepListMetricRelabelConfig)
				} else {
					stringScfgMap["metric_relabel_configs"] = []interface{}{keepListMetricRelabelConfig}
				}

				// Convert back to map[interface{}]interface{} for YAML marshalling
				interfaceScfgMap := make(map[interface{}]interface{})
				for k, v := range stringScfgMap {
					interfaceScfgMap[k] = v
				}

				// Update the scrape_configs list
				scrapeConfigs[i] = interfaceScfgMap
			}
		}

		// Write updated scrape_configs back to config
		config["scrape_configs"] = scrapeConfigs
	} else {
		fmt.Println("No 'scrape_configs' found in the YAML. Skipping updates.")
		return nil
	}

	cfgYamlWithMetricRelabelConfig, err := yaml.Marshal(config)
	if err != nil {
		return fmt.Errorf("error marshalling YAML for %s: %v. The keep list regex will not be used", yamlConfigFile, err)
	}

	if err := os.WriteFile(yamlConfigFile, cfgYamlWithMetricRelabelConfig, os.ModePerm); err != nil {
		return fmt.Errorf("error writing to file %s: %v. The keep list regex will not be used", yamlConfigFile, err)
	}

	return nil
}