feat: add shutdown endpoint to internal keyper API

rolling-shutter/keyper/kprapi/http.go

@@ -31,6 +31,13 @@ func (srv *server) Ping(w http.ResponseWriter, _ *http.Request) {
 	_, _ = w.Write([]byte("pong"))
 }
 
+func (srv *server) Shutdown(_ http.ResponseWriter, _ *http.Request) {
+	srv.shutdownSig <- struct{}{}
+	// We still want to return here and thus return 200 to the caller after this.
+	// Not immediately closing open connctions is taken care
+	// of by the graceful shutdown of the http server.
+}
+
 func (srv *server) GetDecryptionKey(w http.ResponseWriter, r *http.Request, eon int, epochID kproapi.EpochID) {
 	ctx := r.Context()
 	db := database.New(srv.dbpool)

rolling-shutter/keyper/kprapi/kprapi.go

@@ -3,6 +3,7 @@ package kprapi
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"os"
 	"time"
@@ -33,11 +34,14 @@ type Config interface {
 }
 
 type server struct {
-	dbpool *pgxpool.Pool
-	config Config
-	p2p    P2PMessageSender
+	dbpool      *pgxpool.Pool
+	config      Config
+	p2p         P2PMessageSender
+	shutdownSig chan struct{}
 }
 
+var ErrShutdownRequested = errors.New("shutdown requested from API")
+
 func NewHTTPService(dbpool *pgxpool.Pool, config Config, p2p P2PMessageSender) service.Service {
 	return &server{
 		dbpool: dbpool,
@@ -90,7 +94,13 @@ func (srv *server) Start(ctx context.Context, runner service.Runner) error {
 		Handler:           srv.setupRouter(),
 		ReadHeaderTimeout: 5 * time.Second,
 	}
+	srv.shutdownSig = make(chan struct{})
+	runner.Defer(func() { close(srv.shutdownSig) })
+
 	runner.Go(httpServer.ListenAndServe)
+	runner.Go(func() error {
+		return srv.waitShutdown(ctx)
+	})
 	runner.Go(func() error {
 		<-ctx.Done()
 		shutdownCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
@@ -100,6 +110,24 @@ func (srv *server) Start(ctx context.Context, runner service.Runner) error {
 	return nil
 }
 
+func (srv *server) waitShutdown(ctx context.Context) error {
+	for {
+		select {
+		case _, ok := <-srv.shutdownSig:
+			if !ok {
+				// channel close without a send
+				// means we want to stop the shutdown waiter
+				// but not stop execution
+				return nil
+			}
+			return ErrShutdownRequested
+		case <-ctx.Done():
+			// we canceled somewhere else
+			return nil
+		}
+	}
+}
+
 func (srv *server) setupAPIRouter(swagger *openapi3.T) http.Handler {
 	router := chi.NewRouter()
 

rolling-shutter/keyper/kproapi/oapi.yaml

@@ -16,6 +16,13 @@ paths:
       operationId: ping
       parameters:
 
+  /shutdown:
+    post:
+      description: |
+        Shut down the served
+      operationId: shutdown
+      parameters:
+
   /eons:
     get:
       description: |