Enhanced flexibility in Consul Catalog configuration

provider/consul/consul_catalog.go

@@ -1,6 +1,7 @@
 package consul
 
 import (
+	"bytes"
 	"errors"
 	"sort"
 	"strconv"
@@ -31,7 +32,9 @@ type CatalogProvider struct {
 	Endpoint              string `description:"Consul server endpoint"`
 	Domain                string `description:"Default domain used"`
 	Prefix                string `description:"Prefix used for Consul catalog tags"`
+	FrontEndRule          string `description:"Frontend rule used for Consul services"`
 	client                *api.Client
+	frontEndRuleTemplate  *template.Template
 }
 
 type serviceUpdate struct {
@@ -137,9 +140,9 @@ func (p *CatalogProvider) healthyNodes(service string) (catalogUpdate, error) {
 	}
 
 	nodes := fun.Filter(func(node *api.ServiceEntry) bool {
-		constraintTags := p.getContraintTags(node.Service.Tags)
+		constraintTags := p.getConstraintTags(node.Service.Tags)
 		ok, failingConstraint := p.MatchConstraints(constraintTags)
-		if ok == false && failingConstraint != nil {
+		if !ok && failingConstraint != nil {
 			log.Debugf("Service %v pruned by '%v' constraint", service, failingConstraint.String())
 		}
 		return ok
@@ -162,6 +165,13 @@ func (p *CatalogProvider) healthyNodes(service string) (catalogUpdate, error) {
 	}, nil
 }
 
+func (p *CatalogProvider) getPrefixedName(name string) string {
+	if len(p.Prefix) > 0 {
+		return p.Prefix + "." + name
+	}
+	return name
+}
+
 func (p *CatalogProvider) getEntryPoints(list string) []string {
 	return strings.Split(list, ",")
 }
@@ -172,10 +182,35 @@ func (p *CatalogProvider) getBackend(node *api.ServiceEntry) string {
 
 func (p *CatalogProvider) getFrontendRule(service serviceUpdate) string {
 	customFrontendRule := p.getAttribute("frontend.rule", service.Attributes, "")
-	if customFrontendRule != "" {
-		return customFrontendRule
+	if customFrontendRule == "" {
+		customFrontendRule = p.FrontEndRule
 	}
-	return "Host:" + service.ServiceName + "." + p.Domain
+
+	t := p.frontEndRuleTemplate
+	t, err := t.Parse(customFrontendRule)
+	if err != nil {
+		log.Errorf("failed to parse Consul Catalog custom frontend rule: %s", err)
+		return ""
+	}
+
+	templateObjects := struct {
+		ServiceName string
+		Domain      string
+		Attributes  []string
+	}{
+		ServiceName: service.ServiceName,
+		Domain:      p.Domain,
+		Attributes:  service.Attributes,
+	}
+
+	var buffer bytes.Buffer
+	err = t.Execute(&buffer, templateObjects)
+	if err != nil {
+		log.Errorf("failed to execute Consul Catalog custom frontend rule template: %s", err)
+		return ""
+	}
+
+	return buffer.String()
 }
 
 func (p *CatalogProvider) getBackendAddress(node *api.ServiceEntry) string {
@@ -201,22 +236,42 @@ func (p *CatalogProvider) getBackendName(node *api.ServiceEntry, index int) stri
 }
 
 func (p *CatalogProvider) getAttribute(name string, tags []string, defaultValue string) string {
+	return p.getTag(p.getPrefixedName(name), tags, defaultValue)
+}
+
+func (p *CatalogProvider) hasTag(name string, tags []string) bool {
+	// Very-very unlikely that a Consul tag would ever start with '=!='
+	tag := p.getTag(name, tags, "=!=")
+	return tag != "=!="
+}
+
+func (p *CatalogProvider) getTag(name string, tags []string, defaultValue string) string {
 	for _, tag := range tags {
-		if strings.Index(strings.ToLower(tag), p.Prefix+".") == 0 {
-			if kv := strings.SplitN(tag[len(p.Prefix+"."):], "=", 2); len(kv) == 2 && strings.ToLower(kv[0]) == strings.ToLower(name) {
-				return kv[1]
+		// Given the nature of Consul tags, which could be either singular markers, or key=value pairs, we check if the consul tag starts with 'name'
+		if strings.Index(strings.ToLower(tag), strings.ToLower(name)) == 0 {
+			// In case, where a tag might be a key=value, try to split it by the first '='
+			// - If the first element (which would always be there, even if the tag is a singular marker without '=' in it
+			if kv := strings.SplitN(tag, "=", 2); strings.ToLower(kv[0]) == strings.ToLower(name) {
+				// If the returned result is a key=value pair, return the 'value' component
+				if len(kv) == 2 {
+					return kv[1]
+				}
+				// If the returned result is a singular marker, return the 'key' component
+				return kv[0]
 			}
 		}
 	}
 	return defaultValue
 }
 
-func (p *CatalogProvider) getContraintTags(tags []string) []string {
+func (p *CatalogProvider) getConstraintTags(tags []string) []string {
 	var list []string
 
 	for _, tag := range tags {
-		if strings.Index(strings.ToLower(tag), p.Prefix+".tags=") == 0 {
-			splitedTags := strings.Split(tag[len(p.Prefix+".tags="):], ",")
+		// If 'AllTagsConstraintFiltering' is disabled, we look for a Consul tag named 'traefik.tags' (unless different 'prefix' is configured)
+		if strings.Index(strings.ToLower(tag), p.getPrefixedName("tags=")) == 0 {
+			// If 'traefik.tags=' tag is found, take the tag value and split by ',' adding the result to the list to be returned
+			splitedTags := strings.Split(tag[len(p.getPrefixedName("tags=")):], ",")
 			list = append(list, splitedTags...)
 		}
 	}
@@ -231,6 +286,8 @@ func (p *CatalogProvider) buildConfig(catalog []catalogUpdate) *types.Configurat
 		"getBackendName":       p.getBackendName,
 		"getBackendAddress":    p.getBackendAddress,
 		"getAttribute":         p.getAttribute,
+		"getTag":               p.getTag,
+		"hasTag":               p.hasTag,
 		"getEntryPoints":       p.getEntryPoints,
 		"hasMaxconnAttributes": p.hasMaxconnAttributes,
 	}
@@ -326,6 +383,16 @@ func (p *CatalogProvider) watch(configurationChan chan<- types.ConfigMessage, st
 	}
 }
 
+func (p *CatalogProvider) setupFrontEndTemplate() {
+	var FuncMap = template.FuncMap{
+		"getAttribute": p.getAttribute,
+		"getTag":       p.getTag,
+		"hasTag":       p.hasTag,
+	}
+	t := template.New("consul catalog frontend rule").Funcs(FuncMap)
+	p.frontEndRuleTemplate = t
+}
+
 // Provide allows the consul catalog provider to provide configurations to traefik
 // using the given configuration channel.
 func (p *CatalogProvider) Provide(configurationChan chan<- types.ConfigMessage, pool *safe.Pool, constraints types.Constraints) error {
@@ -337,6 +404,7 @@ func (p *CatalogProvider) Provide(configurationChan chan<- types.ConfigMessage,
 	}
 	p.client = client
 	p.Constraints = append(p.Constraints, constraints...)
+	p.setupFrontEndTemplate()
 
 	pool.Go(func(stop chan bool) {
 		notify := func(err error, time time.Duration) {