Merge pull request #610 from nlgotz/ng/consul-target-name

feat: Templated names and tags for Consul targets

Author: karimra

docs/user_guide/targets/target_discovery/consul_discovery.md

@@ -23,6 +23,28 @@ loader:
         password: admin
 ```
 
+### Templating with Consul
+
+It is possible to set the target name to something other than the Consul Service ID using the `name` field under the config. The target name can be customized using [Go Templates](https://golang.org/pkg/text/template/).
+
+In addition to setting the target name, it is also possible to use Go Templates on `event-tags` as well.
+
+The templates use the Service under Consul, so access to things like `ID`, `Tags`, `Meta`, etc. are all available.
+
+```yaml
+loader:
+  type: consul
+  services:
+    - name: cluster1-gnmi-server
+      config:
+        name: "{{.Meta.device}}"
+        event-tags:
+            location: "{{.Meta.site_name}}"
+            model: "{{.Meta.device_type}}"
+            tag-1: "{{.Meta.tag_1}}"
+            boring-static-tag: "hello"
+```
+
 ### Configuration
 
 ```yaml

pkg/config/loader.go

@@ -50,7 +50,6 @@ func (c *Config) GetLoader() error {
 					}
 					return os.ExpandEnv(v)
 				})
-				fmt.Printf("LOADER: %+v\n", c.Loader)
 				return nil
 			}
 		}

pkg/loaders/consul_loader/consul_loader.go

@@ -9,6 +9,7 @@
 package consul_loader
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -17,7 +18,9 @@ import (
 	"log"
 	"net"
 	"strconv"
+	"strings"
 	"sync"
+	"text/template"
 	"time"
 
 	"gopkg.in/yaml.v2"
@@ -110,6 +113,8 @@ type serviceDef struct {
 	Config map[string]interface{} `mapstructure:"config,omitempty" json:"config,omitempty"`
 
 	tags map[string]struct{}
+	targetNameTemplate *template.Template
+	targetTagsTemplate map[string]*template.Template
 }
 
 func (c *consulLoader) Init(ctx context.Context, cfg map[string]interface{}, logger *log.Logger, opts ...loaders.Option) error {
@@ -403,7 +408,54 @@ SRV:
 			tc.Address = se.Node.Address
 		}
 		tc.Address = net.JoinHostPort(tc.Address, strconv.Itoa(se.Service.Port))
+		
+		var buffer bytes.Buffer
+
 		tc.Name = se.Service.ID
+
+		if configName, ok := sd.Config["name"].(string); ok {
+			nameTemplate, err := template.New("targetName").Option("missingkey=zero").Parse(configName)
+			if err != nil {
+				c.logger.Println("Could not parse nameTemplate")
+			}
+			sd.targetNameTemplate = nameTemplate
+			
+			buffer.Reset()
+			err = sd.targetNameTemplate.Execute(&buffer, se.Service)
+			if err != nil {
+				c.logger.Println("Could not execute nameTemplate")
+				continue
+			}
+			tc.Name = buffer.String()
+		}
+
+		// Create Event tags from Consul via templates
+		if configEventTags, ok := sd.Config["event-tags"].(map[string]interface{}); ok {
+			// Allow to use join function in tags
+			templateFunctions := template.FuncMap{"join": strings.Join}
+
+			sd.targetTagsTemplate = make(map[string]*template.Template)
+			for tagName, tagTemplateString := range configEventTags {
+				tagTemplate, err := template.New(tagName).Funcs(templateFunctions).Option("missingkey=zero").Parse(fmt.Sprintf("%v",tagTemplateString))
+				if err != nil {
+					c.logger.Println("Could not parse tagTemplate:", tagName)
+					continue
+				}
+				sd.targetTagsTemplate[tagName] = tagTemplate
+			}
+
+			eventTags := make(map[string]string)
+			for tagName, tagTemplate := range sd.targetTagsTemplate {
+				buffer.Reset()
+				err := tagTemplate.Execute(&buffer, se.Service)
+				if err != nil {
+					c.logger.Println("Could not execute tagTemplate:", tagName)
+					return nil, err
+				}
+				eventTags[tagName] = buffer.String()
+			}
+			tc.EventTags = eventTags
+		}
 		return tc, nil
 	}