From 559bccccd40d028e412d9f11709ded0250ba6dcd Mon Sep 17 00:00:00 2001
From: Linus Nordberg <linus@nordberg.se>
Date: Tue, 24 May 2022 23:33:38 +0200
Subject: implement primary and secondary role, for replication

---
 internal/node/handler/handler.go | 91 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 internal/node/handler/handler.go

(limited to 'internal/node/handler/handler.go')

diff --git a/internal/node/handler/handler.go b/internal/node/handler/handler.go
new file mode 100644
index 0000000..2871c5d
--- /dev/null
+++ b/internal/node/handler/handler.go
@@ -0,0 +1,91 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"git.sigsum.org/sigsum-go/pkg/log"
+	"git.sigsum.org/sigsum-go/pkg/types"
+)
+
+type Config interface {
+	Prefix() string
+	LogID() string
+	Deadline() time.Duration
+}
+
+// Handler implements the http.Handler interface
+type Handler struct {
+	Config
+	Fun      func(context.Context, Config, http.ResponseWriter, *http.Request) (int, error)
+	Endpoint types.Endpoint
+	Method   string
+}
+
+// Path returns a path that should be configured for this handler
+func (h Handler) Path() string {
+	if len(h.Prefix()) == 0 {
+		return h.Endpoint.Path("", "sigsum", "v0")
+	}
+	return h.Endpoint.Path("", h.Prefix(), "sigsum", "v0")
+}
+
+// ServeHTTP is part of the http.Handler interface
+func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	start := time.Now()
+	code := 0
+	defer func() {
+		end := time.Now().Sub(start).Seconds()
+		sc := fmt.Sprintf("%d", code)
+
+		rspcnt.Inc(h.LogID(), string(h.Endpoint), sc)
+		latency.Observe(end, h.LogID(), string(h.Endpoint), sc)
+	}()
+	reqcnt.Inc(h.LogID(), string(h.Endpoint))
+
+	code = h.verifyMethod(w, r)
+	if code != 0 {
+		return
+	}
+	h.handle(w, r)
+}
+
+// verifyMethod checks that an appropriate HTTP method is used and
+// returns 0 if so, or an HTTP status code if not.  Error handling is
+// based on RFC 7231, see Sections 6.5.5 (Status 405) and 6.5.1
+// (Status 400).
+func (h Handler) verifyMethod(w http.ResponseWriter, r *http.Request) int {
+	checkHTTPMethod := func(m string) bool {
+		return m == http.MethodGet || m == http.MethodPost
+	}
+
+	if h.Method == r.Method {
+		return 0
+	}
+
+	code := http.StatusBadRequest
+	if ok := checkHTTPMethod(r.Method); ok {
+		w.Header().Set("Allow", h.Method)
+		code = http.StatusMethodNotAllowed
+	}
+
+	http.Error(w, fmt.Sprintf("error=%s", http.StatusText(code)), code)
+	return code
+}
+
+// handle handles an HTTP request for which the HTTP method is already verified
+func (h Handler) handle(w http.ResponseWriter, r *http.Request) {
+	deadline := time.Now().Add(h.Deadline())
+	ctx, cancel := context.WithDeadline(r.Context(), deadline)
+	defer cancel()
+
+	code, err := h.Fun(ctx, h.Config, w, r)
+	if err != nil {
+		log.Debug("%s/%s: %v", h.Prefix(), h.Endpoint, err)
+		http.Error(w, fmt.Sprintf("error=%s", err.Error()), code)
+	} else if code != 200 {
+		w.WriteHeader(code)
+	}
+}
-- 
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