Add consul_key function to integrate concul with hcl2 tempaltes. (#10119)

* Add consul_key function to integrate concul with hcl2 tempaltes.
* sidebar nav

common/template/funcs.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"sync"
 
+	consulapi "github.com/hashicorp/consul/api"
 	vaultapi "github.com/hashicorp/vault/api"
 )
 
@@ -61,3 +62,27 @@ func Vault(path string, key string) (string, error) {
 	}
 	return "", errors.New("Vault path does not contain the requested key")
 }
+
+func Consul(k string) (string, error) {
+	consulConfig := consulapi.DefaultConfig()
+	client, err := consulapi.NewClient(consulConfig)
+	if err != nil {
+		return "", fmt.Errorf("error getting consul client: %s", err)
+	}
+
+	q := &consulapi.QueryOptions{}
+	kv, _, err := client.KV().Get(k, q)
+	if err != nil {
+		return "", fmt.Errorf("error reading consul key: %s", err)
+	}
+	if kv == nil {
+		return "", fmt.Errorf("key does not exist at the given path: %s", k)
+	}
+
+	value := string(kv.Value)
+	if value == "" {
+		return "", fmt.Errorf("value is empty at path %s", k)
+	}
+
+	return value, nil
+}

hcl2template/function/Consul.go

@@ -0,0 +1,25 @@
+package function
+
+import (
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/function"
+
+	commontpl "github.com/hashicorp/packer/common/template"
+)
+
+// ConsulFunc constructs a function that retrieves KV secrets from HC vault
+var ConsulFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "key",
+			Type: cty.String,
+		},
+	},
+	Type: function.StaticReturnType(cty.String),
+	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
+		key := args[0].AsString()
+		val, err := commontpl.Consul(key)
+
+		return cty.StringVal(val), err
+	},
+})

hcl2template/functions.go

@@ -46,6 +46,7 @@ func Functions(basedir string) map[string]function.Function {
 		"coalescelist":    stdlib.CoalesceListFunc,
 		"compact":         stdlib.CompactFunc,
 		"concat":          stdlib.ConcatFunc,
+		"consul_key":      pkrfunction.ConsulFunc,
 		"contains":        stdlib.ContainsFunc,
 		"convert":         typeexpr.ConvertFunc,
 		"csvdecode":       stdlib.CSVDecodeFunc,

template/interpolate/funcs.go

@@ -10,7 +10,6 @@ import (
 	"text/template"
 	"time"
 
-	consulapi "github.com/hashicorp/consul/api"
 	commontpl "github.com/hashicorp/packer/common/template"
 	"github.com/hashicorp/packer/common/uuid"
 	"github.com/hashicorp/packer/helper/common"
@@ -250,34 +249,14 @@ func funcGenPackerVersion(ctx *Context) interface{} {
 }
 
 func funcGenConsul(ctx *Context) interface{} {
-	return func(k string) (string, error) {
+	return func(key string) (string, error) {
 		if !ctx.EnableEnv {
 			// The error message doesn't have to be that detailed since
 			// semantic checks should catch this.
 			return "", errors.New("consul_key is not allowed here")
 		}
 
-		consulConfig := consulapi.DefaultConfig()
-		client, err := consulapi.NewClient(consulConfig)
-		if err != nil {
-			return "", fmt.Errorf("error getting consul client: %s", err)
-		}
-
-		q := &consulapi.QueryOptions{}
-		kv, _, err := client.KV().Get(k, q)
-		if err != nil {
-			return "", fmt.Errorf("error reading consul key: %s", err)
-		}
-		if kv == nil {
-			return "", fmt.Errorf("key does not exist at the given path: %s", k)
-		}
-
-		value := string(kv.Value)
-		if value == "" {
-			return "", fmt.Errorf("value is empty at path %s", k)
-		}
-
-		return value, nil
+		return commontpl.Consul(key)
 	}
 }
 

website/data/docs-navigation.js

@@ -33,6 +33,7 @@ export default [
             category: 'contextual',
             content: [
               'vault',
+              'consul',
             ],
           },
           {

website/pages/docs/from-1.5/functions/contextual/consul.mdx

@@ -0,0 +1,42 @@
+---
+layout: docs
+page_title: consul - Functions - Configuration Language
+sidebar_title: consul
+description: The consul function retrieves secrets from HashiCorp consul KV stores.
+---
+
+
+# `consul_key` Function
+
+[Consul](https://www.consul.io) keys can be used within your template using the
+`consul_key` function.
+
+You can either use this function in a locals block or directly inline where you
+want to use the value.
+
+```hcl
+locals {
+  my_version = "${consul_key("myservice/version")}"
+}
+
+source "null" "first-example" {
+  communicator = "none"
+}
+
+build {
+  name = "my-build-name"
+  sources = ["null.first-example"]
+
+  provisioner "shell-local" {
+    environment_vars = ["TESTVAR=${build.PackerRunUUID}"]
+    inline = ["echo my_version is '${local.my_version}'",
+              "echo version is '${consul_key("myservice/version")}'."]
+  }
+}
+```
+
+This will load the key stored at the path `myservice/version` from consul.
+
+The configuration for consul (address, tokens, ...) must be specified as
+environment variables, as specified in the
+[Documentation](https://www.consul.io/docs/commands#environment-variables).