Adding approval process

README.org

@@ -2,4 +2,47 @@
 #+AUTHOR: Adam Mohammed
 
 
-This provides a way to do k8s native application deployment in a way that's simple and requires almost no configuration
+Service Demon is a centralized configuration provider for Nautilus services.
+
+This provides a way to do k8s native application deployment in a way that's simple
+and requires almost no configuration on the client.
+
+
+Service Demon runs in k8s and expects a service agent to be deployed alongside
+your application.
+
+
+** Workflow
+
+This demon (playing off of "daemon") hosts an application registration process that,
+the our agent is aware of. By simply deploying the agent in your namespace, it will kick off
+the application registration process. On completion, the agent is able to respond to commands
+from the configuration service to update k8s resources that your application can rely on.
+
+
+The agent on deploy, will use TLS certificates generated for your applications ingress to
+announce itself as an application that wishes to be registered.
+
+Once the app announces that it would like to be registered, an authorized human must approve
+the application.
+
+Once the approval goes through, the application is registered, and can start to request application
+configuration manifests.
+
+The agent will fetch the manifests it needs and store them by talking to the k8s api. It will create
+configuration maps, secrets, and other resources as necessary.
+
+
+From there a client library loaded into your application will know how to read those manifests
+and provide some baseline functionality to your service.
+
+
+** Motivation
+
+Although microservices are autonomous, they rely on common infrastructure to
+reduce the operational overhead on the team maintaining them. Right now,
+Nautilus has trouble performing authentication and authorization checks,
+particularly between services.
+
+By using a central configuration store, we can deploy and manage authorization policies
+centrally, and push them down to the active services, so we can control authorization at runtime.

cmd/hub/main.go

@@ -1,74 +1,78 @@
 package main
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
-	"fmt"
-	"io/ioutil"
+	"crypto/tls"
+	"crypto/x509"
+	"io"
+	"log"
 	"net/http"
 	"os"
 
-	"golang.org/x/oauth2"
-
-	"go.fixergrid.net/servicedemon/pkg/discord"
+	"go.fixergrid.net/servicedemon/pkg/pubsub"
+	"go.fixergrid.net/servicedemon/pkg/registrar"
 )
 
-func main() {
-	fmt.Println("Starting .... the >HUB<")
-
-	token, isSet := os.LookupEnv("DISCORD_BOT_TOKEN")
-	if !isSet {
-		fmt.Println("please set the environment variable 'DISCORD_BOT_TOKEN'")
-		return
-	}
-
-	tokensrc := oauth2.StaticTokenSource(&oauth2.Token{
-		AccessToken: token,
-		TokenType:   "Bot",
-	})
-
-	ctx := context.Background()
-
-	client := discord.
-		NewClient(ctx, tokensrc).
-		WithDefaultChannel("1125162127133523978")
-
-	resp, err := client.Get("https://discord.com/api/v10/channels/1125162127133523978")
-	if err != nil {
-		fmt.Printf("there was an error making the request: %v\n", err)
-		return
-	}
-
-	out, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		fmt.Printf("failed to read response body: %v\n", err)
-		return
-	}
-
-	fmt.Printf("Got response:\n%s\n", out)
-
-	messageContent := map[string]interface{}{
-		"content": "Hello, world!",
-	}
-
-	b, err := json.Marshal(messageContent)
-	if err != nil {
-		fmt.Printf("failed to marshal message: %v\n", err)
-		return
-	}
-
-	r2, err := client.Post("https://discord.com/api/v10/channels/1125162127133523978/messages", "application/json", bytes.NewReader(b))
-	if err != nil {
-		fmt.Printf("failed tdo send message to server: %v\n", err)
-		return
-	}
-
-	out, err = ioutil.ReadAll(r2.Body)
-	if err != nil {
-		fmt.Printf("failed to read response body on send message: %v\n", err)
-		return
-	}
-
-	fmt.Printf("status: %v - res: %v\n", r2.Status, out)
+type noopHandler struct {
+	http.HandlerFunc
+}
+
+func wrapHandlefunc(h http.HandlerFunc) noopHandler {
+	return noopHandler{
+		HandlerFunc: h,
+	}
+}
+
+func (h noopHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	h.HandlerFunc(w, req)
+}
+func main() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	logger := log.New(os.Stdout, "main: ", log.LstdFlags|log.Lshortfile)
+	logger.Println("Starting .... the >HUB<")
+
+	pubsub := pubsub.New()
+	repo := registrar.NewRepo()
+
+	r := registrar.NewRegistrar(
+		pubsub,
+		repo,
+		registrar.WithLogger(log.New(os.Stdout, "registrar: ", log.LstdFlags|log.Lshortfile)),
+	)
+	al := registrar.NewApprovalListener(
+		pubsub,
+		nil,
+		registrar.OptionLog(log.New(os.Stdout, "approvalListener: ", log.LstdFlags|log.Lshortfile)),
+	)
+	go al.Run(ctx)
+
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("/register", r.HandleRegistration)
+	mux.Handle("/approvals/", http.StripPrefix("/approvals/", wrapHandlefunc(r.HandleApproval)))
+
+	certFile, err := os.Open("./certs/ca.pem")
+	if err != nil {
+		logger.Fatalf("failed to open ca.pem: %v", err)
+	}
+
+	caCert, err := io.ReadAll(certFile)
+	if err != nil {
+		logger.Fatalf("failed to read in ca: %v", err)
+	}
+
+	pool := x509.NewCertPool()
+	pool.AppendCertsFromPEM(caCert)
+
+	server := &http.Server{
+		Addr: ":3001",
+		TLSConfig: &tls.Config{
+			ClientCAs:  pool,
+			ClientAuth: tls.RequireAndVerifyClientCert,
+		},
+	}
+	server.Handler = mux
+	log.Println(server.ListenAndServeTLS("./certs/combined.pem", "./certs/server-key.pem"))
 }

go.mod

@@ -3,16 +3,19 @@ module go.fixergrid.net/servicedemon
 go 1.20
 
 require (
-	github.com/bwmarrin/discordgo v0.27.1
+	github.com/slack-go/slack v0.12.2
+	github.com/stretchr/testify v1.8.4
 	golang.org/x/oauth2 v0.9.0
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/google/uuid v1.3.0 // indirect
 	github.com/gorilla/websocket v1.4.2 // indirect
-	golang.org/x/crypto v0.10.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/net v0.11.0 // indirect
-	golang.org/x/sys v0.9.0 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/protobuf v1.28.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,31 +1,34 @@
-github.com/bwmarrin/discordgo v0.27.1 h1:ib9AIc/dom1E/fSIulrBwnez0CToJE113ZGt4HoliGY=
-github.com/bwmarrin/discordgo v0.27.1/go.mod h1:NJZpH+1AfhIcyQsPeuBKsUtYrRnjkyu0kIVMCHkZtRY=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-test/deep v1.0.4 h1:u2CU3YKy9I2pmu9pX0eq50wCgjfGIt539SqR7FbHiho=
+github.com/go-test/deep v1.0.4/go.mod h1:wGDj63lr65AM2AQyKZd/NYHGb0R+1RLqB8NKt3aSFNA=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
 github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
 github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
 github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/slack-go/slack v0.12.2 h1:x3OppyMyGIbbiyFhsBmpf9pwkUzMhthJMRNmNlA4LaQ=
+github.com/slack-go/slack v0.12.2/go.mod h1:hlGi5oXA+Gt+yWTPP0plCdRKmjsDxecdHxYQdlMQKOw=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
-golang.org/x/crypto v0.10.0 h1:LKqV2xt9+kDzSTfOhx4FrkEBcMrAgHSYgzywV9zcGmM=
-golang.org/x/crypto v0.10.0/go.mod h1:o4eNf7Ede1fv+hwOwZsTHl9EsPFO6q6ZvYR8vYfY45I=
 golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.11.0 h1:Gi2tvZIJyBtO9SDr1q9h5hEQCp/4L2RQ+ar0qjx2oNU=
 golang.org/x/net v0.11.0/go.mod h1:2L/ixqYpgIVXmeoSA/4Lu7BzTG4KIyPIryS4IsOd1oQ=
 golang.org/x/oauth2 v0.9.0 h1:BPpt2kU7oMRq3kCHAA1tbSEshXRw1LpG2ztgDwrzuAs=
 golang.org/x/oauth2 v0.9.0/go.mod h1:qYgFZaFiu6Wg24azG8bdV52QJXJGbZzIIsRCdVKzbLw=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.9.0 h1:KS/R3tvhPqvJvwcKfnBHJwwthS11LRhmM5D59eEXa0s=
-golang.org/x/sys v0.9.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
@@ -34,3 +37,7 @@ google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp0
 google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
 google.golang.org/protobuf v1.28.0 h1:w43yiav+6bVFTBQFZX0r7ipe9JQ1QsbMgHwbBziscLw=
 google.golang.org/protobuf v1.28.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

pkg/pubsub/pubsub.go

@@ -0,0 +1,51 @@
+package pubsub
+
+import "sync"
+
+type Pubsub struct {
+	mu     sync.RWMutex
+	subs   map[string][]chan string
+	closed bool
+}
+
+func New() *Pubsub {
+	ps := Pubsub{}
+	ps.subs = make(map[string][]chan string)
+	return &ps
+}
+
+func (ps *Pubsub) Publish(topic string, msg string) {
+	ps.mu.RLock()
+	defer ps.mu.RUnlock()
+
+	if ps.closed {
+		return
+	}
+
+	for _, ch := range ps.subs[topic] {
+		ch <- msg
+	}
+}
+
+func (ps *Pubsub) Subscribe(topic string) <-chan string {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+
+	ch := make(chan string, 1)
+	ps.subs[topic] = append(ps.subs[topic], ch)
+	return ch
+}
+
+func (ps *Pubsub) Close() {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+
+	if !ps.closed {
+		ps.closed = true
+		for _, subs := range ps.subs {
+			for _, ch := range subs {
+				close(ch)
+			}
+		}
+	}
+}

pkg/registrar/approval.go

@@ -0,0 +1,87 @@
+package registrar
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"github.com/google/uuid"
+	svc "go.fixergrid.net/servicedemon/pkg/registrar/internal/services"
+)
+
+const APPROVAL_TOPIC = "net.fixergrid.events.app.approved"
+
+type ApprovalListener struct {
+	svc.ApprovalRequester
+	svc.PubSub
+	svc.AppRepo
+	log internalLog
+}
+
+type option func(r *ApprovalListener)
+
+func OptionLog(l logger) option {
+	return func(r *ApprovalListener) {
+		r.log = internalLog{l}
+	}
+}
+
+func NewApprovalListener(ps svc.PubSub, requester svc.ApprovalRequester, options ...option) ApprovalListener {
+	out := ApprovalListener{
+		PubSub:            ps,
+		ApprovalRequester: requester,
+	}
+
+	for _, opt := range options {
+		opt(&out)
+	}
+	return out
+}
+
+func (a ApprovalListener) Run(ctx context.Context) {
+	newAppEvents := a.Subscribe(REGISTRATION_TOPIC)
+	approvalEvents := a.Subscribe(APPROVAL_TOPIC)
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case event := <-newAppEvents:
+			msg, err := readMessage(event)
+			if err != nil {
+				a.log.Printf("failed to read message: got '%s': %v", event, err)
+			}
+			a.SendApprovalRequest(msg["name"])
+		case event := <-approvalEvents:
+			msg, err := readMessage(event)
+			if err != nil {
+				a.log.Printf("approvalevent: failed to read message: got '%s': %v", event, err)
+			}
+			id := uuid.MustParse(msg["id"])
+			a.HandleApprovedRequest(id)
+		}
+	}
+}
+
+func (a ApprovalListener) SendApprovalRequest(name string) {
+	a.log.Printf("sent approval message for [%s]", name)
+}
+
+func (a ApprovalListener) HandleApprovedRequest(id uuid.UUID) {
+	res, err := a.ApproveApp(id)
+	if err != nil {
+		a.log.Printf("ERROR: couldn't approve request: %v", err)
+		return
+	}
+
+	a.log.Printf("approved application [%s]", res.ID)
+}
+
+func readMessage(event string) (map[string]string, error) {
+	out := map[string]string{}
+
+	err := json.Unmarshal([]byte(event), &out)
+	if err != nil {
+		return nil, fmt.Errorf("readMessage: %w", err)
+	}
+	return out, nil
+}

pkg/registrar/endpoints.go

@@ -0,0 +1,109 @@
+package registrar
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/google/uuid"
+	svc "go.fixergrid.net/servicedemon/pkg/registrar/internal/services"
+)
+
+const (
+	REGISTRATION_TOPIC = "net.fixergrid.events.app.admission"
+)
+
+var validApprover string = "Nautilus Admins"
+
+type Registrar struct {
+	svc.Publisher
+	repo svc.AppRepo
+	log  internalLog
+}
+
+func WithLogger(l logger) RegistrarOpt {
+	return func(r *Registrar) {
+		r.log = internalLog{l}
+	}
+}
+
+type RegistrarOpt func(*Registrar)
+
+func NewRegistrar(publisher svc.Publisher, repo svc.AppRepo, options ...RegistrarOpt) Registrar {
+	r := Registrar{
+		Publisher: publisher,
+		repo:      repo,
+	}
+	for _, opt := range options {
+		opt(&r)
+	}
+	return r
+}
+
+func (r Registrar) HandleRegistration(resp http.ResponseWriter, req *http.Request) {
+	cert := req.TLS.PeerCertificates[0]
+
+	name := cert.DNSNames[0]
+	if r.repo.IsRegistered(name) {
+		resp.WriteHeader(http.StatusOK)
+		resp.Write([]byte(`{"status": "registered"}`))
+	} else {
+		id := r.repo.StartAppRegistration(name)
+		event := map[string]string{
+			"id":   id.String(),
+			"name": name,
+			"type": "ApplicationRegistrationSubmitted",
+		}
+
+		r.sendEvent(REGISTRATION_TOPIC, event)
+
+		resp.WriteHeader(http.StatusCreated)
+		fmt.Fprintf(resp, `{"status": "pending_approval"}`)
+	}
+}
+
+func (r Registrar) HandleApproval(resp http.ResponseWriter, req *http.Request) {
+	headers := resp.Header()
+	headers.Set("content-type", "application/json")
+
+	in := req.URL.Path
+	cert := req.TLS.PeerCertificates[0]
+	OUs := cert.Subject.OrganizationalUnit
+
+	var ou string
+	if len(OUs) == 1 {
+		ou = OUs[0]
+	} else {
+		fmt.Fprintf(resp, `{"errors": ["missing OU"]}`)
+		resp.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	if ou != validApprover {
+		fmt.Fprintf(resp, `{"errors": ["approval forbidden"]}`)
+		resp.WriteHeader(http.StatusForbidden)
+		return
+	}
+
+	appID := uuid.MustParse(in)
+
+	event := map[string]string{
+		"id":       appID.String(),
+		"approver": ou,
+		"type":     "ApplicationRegistrationApproved",
+	}
+	r.sendEvent(APPROVAL_TOPIC, event)
+	resp.WriteHeader(http.StatusOK)
+	fmt.Fprintf(resp, `{"status": "registered"}`)
+}
+
+func (r Registrar) sendEvent(topic string, event map[string]string) error {
+	b, err := json.Marshal(event)
+	if err != nil {
+		return fmt.Errorf("registrar: sendEvent: failed to marshal: %w", err)
+	}
+
+	r.log.Printf("sending event: %s", event)
+	r.Publish(topic, string(b))
+	return nil
+}

pkg/registrar/endpoints_test.go

@@ -0,0 +1,155 @@
+package registrar
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.fixergrid.net/servicedemon/pkg/pubsub"
+)
+
+type TestRequest http.Request
+
+func NewTestRequest(t *testing.T, method string, url string, body io.Reader) TestRequest {
+	req, err := http.NewRequest(method, url, body)
+	require.NoError(t, err)
+	return TestRequest(*req)
+}
+func (tr TestRequest) WithFakeTLSState(dnsName string) TestRequest {
+	cert := x509.Certificate{
+		DNSNames: []string{
+			dnsName,
+		},
+	}
+
+	tr.TLS = &tls.ConnectionState{
+		PeerCertificates: []*x509.Certificate{&cert},
+	}
+
+	return tr
+}
+
+func (tr TestRequest) Create() *http.Request {
+	req := http.Request(tr)
+	return &req
+}
+
+type AppState struct {
+	Name  string
+	State string
+}
+type TestAppRepo []AppState
+
+func (repo TestAppRepo) IsRegistered(name string) bool {
+	for _, app := range repo {
+		if name == app.Name && app.State == "registered" {
+			return true
+		}
+	}
+	return false
+}
+
+func (repo TestAppRepo) PendingApprovalCount() int {
+	count := 0
+	for _, app := range repo {
+		if app.State == "pending_approval" {
+			count += 1
+		}
+	}
+	return count
+}
+
+func (repo *TestAppRepo) StartAppRegistration(name string) uuid.UUID {
+	*repo = append(*repo, AppState{
+		Name:  name,
+		State: "pending_approval",
+	})
+	return uuid.New()
+}
+
+func TestHandleRegisterPendingApproval(t *testing.T) {
+	resp := httptest.NewRecorder()
+
+	req := NewTestRequest(t, http.MethodPost, "http://example.com/v1/register", nil).
+		WithFakeTLSState("dev-app-1.delivery.engineering").
+		Create()
+
+	repo := &TestAppRepo{}
+	pubsub := pubsub.New()
+	subscriber := pubsub.Subscribe(REGISTRATION_TOPIC)
+
+	NewRegistrar(pubsub, repo).HandleRegistration(resp, req)
+
+	assert.Equal(t, http.StatusCreated, resp.Code)
+
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+
+	assert.Equal(t, []byte(`{"status": "pending_approval"}`), body)
+
+	assert.Equal(t, 1, repo.PendingApprovalCount())
+
+	expectedEvent := map[string]string{
+		"name": "dev-app-1.delivery.engineering",
+		"type": "ApplicationRegistrationSubmitted",
+	}
+	assertMessage(t, expectedEvent, subscriber)
+}
+
+func TestHandleRegisterAlreadyRegistered(t *testing.T) {
+	resp := httptest.NewRecorder()
+
+	req := NewTestRequest(t, http.MethodPost, "http://example.com/v1/register", nil).
+		WithFakeTLSState("dev-app-1.delivery.engineering").
+		Create()
+
+	pubsub := pubsub.New()
+	repo := &TestAppRepo{
+		AppState{
+			Name:  "dev-app-1.delivery.engineering",
+			State: "registered",
+		},
+	}
+
+	NewRegistrar(pubsub, repo).HandleRegistration(resp, req)
+
+	assert.Equal(t, http.StatusOK, resp.Code)
+
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+
+	assert.Equal(t, []byte(`{"status": "registered"}`), body)
+}
+
+func assertMessage(t *testing.T, expected map[string]string, sender <-chan string) {
+	timer := time.After(2 * time.Second)
+
+	for {
+		select {
+		case msg := <-sender:
+			compareMessage(t, expected, msg)
+			return
+		case <-timer:
+			t.Fatal("failed waiting for message")
+		}
+	}
+}
+
+func compareMessage(t *testing.T, expected map[string]string, observed string) {
+	observedEvent := map[string]string{}
+
+	require.NoError(t, json.Unmarshal([]byte(observed), &observedEvent))
+
+	assert.NotEmpty(t, observedEvent["id"])
+	for k, v := range expected {
+		assert.Equal(t, v, observedEvent[k])
+	}
+}

pkg/registrar/internal/persistence/fake_repo.go

@@ -0,0 +1,59 @@
+package persistence
+
+import (
+	"github.com/google/uuid"
+	svc "go.fixergrid.net/servicedemon/pkg/registrar/internal/services"
+)
+
+type FakeRepo struct {
+	apps []*svc.Application
+}
+
+func NewFakeRepo() *FakeRepo {
+	return &FakeRepo{
+		apps: make([]*svc.Application, 0),
+	}
+}
+func (repo FakeRepo) IsRegistered(name string) bool {
+	for _, app := range repo.apps {
+		if name == app.Name && app.State == "registered" {
+			return true
+		}
+	}
+	return false
+}
+
+func (repo FakeRepo) PendingApprovalCount() int {
+	count := 0
+	for _, app := range repo.apps {
+		if app.State == "pending_approval" {
+			count += 1
+		}
+	}
+	return count
+}
+
+func (repo *FakeRepo) StartAppRegistration(name string) uuid.UUID {
+	repo.apps = append(repo.apps, &svc.Application{
+		Name:  name,
+		State: "pending_approval",
+	})
+	return uuid.New()
+}
+
+func (repo *FakeRepo) ApproveApp(id uuid.UUID) (svc.Application, error) {
+	var app *svc.Application
+
+	for _, application := range repo.apps {
+		if application.ID == id {
+			application.State = "registered"
+		}
+	}
+
+	if app == nil {
+		return svc.Application{}, svc.ErrApplicationNotFound
+	}
+
+	return *app, nil
+
+}

pkg/registrar/internal/services/app_registration.go

@@ -0,0 +1,2 @@
+package services
+

pkg/registrar/internal/services/approvals.go

@@ -0,0 +1,5 @@
+package services
+
+type ApprovalRequester interface {
+	SendApprovalRequest(appName string) error
+}

pkg/registrar/internal/services/pubsub.go

@@ -0,0 +1,14 @@
+package services
+
+type Publisher interface {
+	Publish(topic string, message string)
+}
+
+type PubSub interface {
+	Publisher
+	Subscriber
+}
+
+type Subscriber interface {
+	Subscribe(topic string) <-chan string
+}

pkg/registrar/internal/services/repo.go

@@ -0,0 +1,26 @@
+package services
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+var (
+	ErrAppRepo             = errors.New("AppRepo")
+	ErrApplicationNotFound = fmt.Errorf("%w: application not found", ErrAppRepo)
+)
+
+type Application struct {
+	ID    uuid.UUID
+	Name  string
+	State string
+}
+
+type AppRepo interface {
+	IsRegistered(name string) bool
+	PendingApprovalCount() int
+	StartAppRegistration(name string) uuid.UUID
+	ApproveApp(id uuid.UUID) (Application, error)
+}

pkg/registrar/logging.go

@@ -0,0 +1,33 @@
+package registrar
+
+import "fmt"
+
+type logger interface {
+	Output(int, string) error
+}
+
+type ilogger interface {
+	logger
+	Print(...interface{})
+	Printf(string, ...interface{})
+	Println(...interface{})
+}
+
+type internalLog struct {
+	logger
+}
+
+// Println replicates the behaviour of the standard logger.
+func (t internalLog) Println(v ...interface{}) {
+	t.Output(2, fmt.Sprintln(v...))
+}
+
+// Printf replicates the behaviour of the standard logger.
+func (t internalLog) Printf(format string, v ...interface{}) {
+	t.Output(2, fmt.Sprintf(format, v...))
+}
+
+// Print replicates the behaviour of the standard logger.
+func (t internalLog) Print(v ...interface{}) {
+	t.Output(2, fmt.Sprint(v...))
+}

pkg/registrar/repo.go

@@ -0,0 +1,10 @@
+package registrar
+
+import (
+	persist "go.fixergrid.net/servicedemon/pkg/registrar/internal/persistence"
+	svc "go.fixergrid.net/servicedemon/pkg/registrar/internal/services"
+)
+
+func NewRepo() svc.AppRepo {
+	return persist.NewFakeRepo()
+}