implement header_upstream directive for #4, docs

README.md

@@ -51,6 +51,7 @@ awslambda <path-prefix> {
     name_append        string to append to function name
     single             name of a single lambda function to invoke
     strip_path_prefix  If true, path and function name are stripped from the path
+    header_upstream    header-name header-value
 }
 ```
 
@@ -64,6 +65,13 @@ awslambda <path-prefix> {
 *   **name_append** is an optional string to append to the function name parsed from the URL before invoking the Lambda.
 *   **single** is an optional function name. If set, function name is not parsed from the URI path.
 *   **strip_path_prefix** If 'true', path and function name is stripped from the path sent as request metadata to the Lambda function. (default=false)
+*   **header_upstream** Inject "header" key-value pairs into the upstream request json. Supports usage of [caddyfile placeholders](https://caddyserver.com/docs/placeholders). Can be used multiple times. Comes handy with frameworks like express. Example:
+   ```
+   header_upstream X-API-Secret super1337secretapikey
+   header_upstream X-Forwarded-For {remote}
+   header_upstream X-Forwarded-Host {hostonly}
+   header_upstream X-Forwarded-Proto {scheme}
+   ```
 
 Function names are parsed from the portion of request path following the path-prefix in the
 directive based on this convention: `[path-prefix]/[function-name]/[extra-path-info]` unless `single` attribute is set.
@@ -277,6 +285,7 @@ recompile caddy with the plugin installed:
 
 ```bash
 go get github.com/mholt/caddy/caddy
+go get github.com/caddyserver/builds
 cd $GOPATH/src/github.com/mholt/caddy/caddy
 ```
 

config.go

@@ -10,6 +10,7 @@ import (
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/lambda"
 	"github.com/mholt/caddy"
+	"github.com/mholt/caddy/caddyhttp/httpserver"
 )
 
 // Config specifies configuration for a single awslambda block
@@ -55,6 +56,9 @@ type Config struct {
 	// the RequestMeta.Path would be /foo
 	StripPathPrefix bool
 
+	// headers to set in the upstream "headers" array - caddy placeholders work here
+	UpstreamHeaders map[string][]string
+
 	invoker Invoker
 }
 
@@ -151,6 +155,18 @@ func (c *Config) MaybeToInvokeInput(r *http.Request) (*lambda.InvokeInput, error
 		req.Meta.Path = c.stripPathPrefix(req.Meta.Path, funcName)
 	}
 
+	// inject upstream headers defined with the header_upstream directive into req.Meta.Headers
+	// uses caddy's integrated replacer for placeholder replacement (https://caddyserver.com/docs/placeholders)
+	replInt := r.Context().Value(httpserver.ReplacerCtxKey)
+	replacer := replInt.(httpserver.Replacer)
+	for k, v := range c.UpstreamHeaders {
+		newValue := make([]string, len(v))
+		for i, v := range v {
+			newValue[i] = replacer.Replace(v)
+		}
+		req.Meta.Headers[strings.ToLower(k)] = newValue
+	}
+
 	payload, err := json.Marshal(req)
 	if err != nil {
 		return nil, err
@@ -240,6 +256,12 @@ func ParseConfigs(c *caddy.Controller) ([]*Config, error) {
 		case "exclude":
 			conf.Exclude = append(conf.Exclude, val)
 			conf.Exclude = append(conf.Exclude, c.RemainingArgs()...)
+		case "header_upstream":
+			if conf.UpstreamHeaders == nil {
+				conf.UpstreamHeaders = make(map[string][]string)
+			}
+			value := strings.Join(c.RemainingArgs(), " ")
+			conf.UpstreamHeaders[val] = []string{value}
 		default:
 			last = val
 		}

config_test.go

@@ -2,6 +2,7 @@ package awslambda
 
 import (
 	"bytes"
+	"context"
 	"io"
 	"net/http"
 	"reflect"
@@ -11,6 +12,7 @@ import (
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/service/lambda"
 	"github.com/mholt/caddy"
+	"github.com/mholt/caddy/caddyhttp/httpserver"
 )
 
 func TestAcceptsFunction(t *testing.T) {
@@ -120,6 +122,7 @@ func TestParseConfigs(t *testing.T) {
     name_append    _suffix_here
     single             my-single-func
     strip_path_prefix  on
+    header_upstream    x-real-ip {remote}
 }`,
 			[]*Config{
 				&Config{
@@ -134,6 +137,9 @@ func TestParseConfigs(t *testing.T) {
 					NameAppend:      "_suffix_here",
 					Single:          "my-single-func",
 					StripPathPrefix: true,
+					UpstreamHeaders: map[string][]string{
+						"x-real-ip": []string{"{remote}"},
+					},
 				},
 			},
 		},
@@ -207,6 +213,10 @@ func TestMaybeToInvokeInput(t *testing.T) {
 		NamePrepend: "before-",
 		NameAppend:  "-after",
 		Qualifier:   "prod",
+		UpstreamHeaders: map[string][]string{
+			"x-real-proto":  []string{"{proto}"},
+			"x-real-method": []string{"{method}"},
+		},
 	}
 	input, err := c.MaybeToInvokeInput(r1)
 	if err != nil {
@@ -220,6 +230,8 @@ func TestMaybeToInvokeInput(t *testing.T) {
 	if err != nil {
 		t.Fatalf("NewRequest returned err: %v", err)
 	}
+	req.Meta.Headers["x-real-proto"] = []string{"HTTP/1.1"}
+	req.Meta.Headers["x-real-method"] = []string{"PUT"}
 	expected := lambda.InvokeInput{
 		FunctionName: &funcName,
 		Qualifier:    &c.Qualifier,
@@ -290,5 +302,8 @@ func mustNewRequest(method, path string, body io.Reader) *http.Request {
 	if err != nil {
 		panic(err)
 	}
+	replacer := httpserver.NewReplacer(req, nil, "")
+	newContext := context.WithValue(req.Context(), httpserver.ReplacerCtxKey, replacer)
+	req = req.WithContext(newContext)
 	return req
 }

lambda_test.go

@@ -19,10 +19,7 @@ func TestInvokeOK(t *testing.T) {
 		},
 	}
 	h := initHandler(invoker)
-	r, err := http.NewRequest("POST", "/lambda-test/foo", bytes.NewBufferString("hi"))
-	if err != nil {
-		t.Fatalf("Failed to create request: %v", err)
-	}
+	r := mustNewRequest("POST", "/lambda-test/foo", bytes.NewBufferString("hi"))
 	w := httptest.NewRecorder()
 
 	status, err := h.ServeHTTP(w, r)