indexer: QoL changes to headers

This commit adds some Link headers to indicate to clients next steps to
take and sets errors in the final JSON encode to be sent as trailers.

indexer/httptransport.go

@@ -1,7 +1,6 @@
 package indexer
 
 import (
-	"context"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -18,9 +17,10 @@ import (
 var _ http.Handler = (*HTTP)(nil)
 
 const (
-	IndexAPIPath       = "/api/v1/index_report"
-	IndexReportAPIPath = "/api/v1/index_report/"
-	StateAPIPath       = "/api/v1/state"
+	v1Root             = "/api/v1/"
+	IndexAPIPath       = v1Root + "index_report"
+	IndexReportAPIPath = v1Root + "index_report/"
+	StateAPIPath       = v1Root + "state"
 )
 
 type HTTP struct {
@@ -112,7 +112,13 @@ func (h *HTTP) IndexReportHandler(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+const (
+	linkIndex  = `<%s>; rel="https://projectquay.io/clair/v1/index_report"`
+	linkReport = `<%s>; rel="https://projectquay.io/clair/v1/vulnerability_report"`
+)
+
 func (h *HTTP) IndexHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
 	w.Header().Set("content-type", "application/json")
 	if r.Method != http.MethodPost {
 		resp := &je.Response{
@@ -138,7 +144,7 @@ func (h *HTTP) IndexHandler(w http.ResponseWriter, r *http.Request) {
 
 	// TODO Do we need some sort of background context embedded in the HTTP
 	// struct?
-	report, err := h.serv.Index(context.TODO(), &m)
+	report, err := h.serv.Index(ctx, &m)
 	if err != nil {
 		resp := &je.Response{
 			Code:    "index-error",
@@ -149,16 +155,12 @@ func (h *HTTP) IndexHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	next := path.Join(IndexReportAPIPath, m.Hash.String())
+	w.Header().Add("link", fmt.Sprintf(linkReport, path.Join(v1Root, "vulnerabilty_report", m.Hash.String())))
+	w.Header().Add("link", fmt.Sprintf(linkIndex, next))
 	w.Header().Set("location", next)
 	w.WriteHeader(http.StatusCreated)
-	err = json.NewEncoder(w).Encode(report)
-	if err != nil {
-		resp := &je.Response{
-			Code:    "encoding-error",
-			Message: fmt.Sprintf("failed to encode scan report: %v", err),
-		}
-		je.Error(w, resp, http.StatusInternalServerError)
-		return
+	if err := json.NewEncoder(w).Encode(report); err != nil {
+		w.Header().Set("clair-error", err.Error())
 	}
 }
 
@@ -176,21 +178,14 @@ func (h *HTTP) StateHandler(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusNotModified)
 		return
 	}
-	w.Header().Set("content-type", "application/json")
-
-	err := json.NewEncoder(w).Encode(struct {
-		State string `json:"state"`
-	}{
-		State: s,
-	})
+	err := json.NewEncoder(w).Encode(stateSuccess{s})
 	if err != nil {
-		resp := &je.Response{
-			Code:    "encoding-error",
-			Message: fmt.Sprintf("failed to encode scan report: %v", err),
-		}
-		je.Error(w, resp, http.StatusInternalServerError)
+		w.Header().Set("clair-error", err.Error())
 	}
-	return
+}
+
+type stateSuccess struct {
+	State string `json:"state"`
 }
 
 // Register will register the api on a given mux.