From cd61d9217fc102df6f95e6984b7e7ae0df4c3b75 Mon Sep 17 00:00:00 2001
From: Elis Lulja <elulja@cisco.com>
Date: Mon, 6 Jun 2022 16:33:00 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=A9=B9=20Fix=20issue=20not=20sending=20de?=
 =?UTF-8?q?lete=20events=20on=20etcd=20(#46)?=
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An issue that was preventing the reader from sending `DELETE` service
events when an endpoint was deleted is now fixed.

Signed-off-by: Elis Lulja <elulja@cisco.com>
---
 pkg/cmd/watch/etcd/watcher.go      | 43 ++++++++++++++++++++++++++++--
 pkg/cmd/watch/etcd/watcher_test.go | 12 +--------
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/pkg/cmd/watch/etcd/watcher.go b/pkg/cmd/watch/etcd/watcher.go
index b36c4bb..99efcbc 100644
--- a/pkg/cmd/watch/etcd/watcher.go
+++ b/pkg/cmd/watch/etcd/watcher.go
@@ -19,10 +19,14 @@
 package etcd
 
 import (
+	"bytes"
 	"context"
+	"errors"
 	"fmt"
 
+	"github.com/CloudNativeSDWAN/cnwan-operator/pkg/servregistry"
 	opsr "github.com/CloudNativeSDWAN/cnwan-operator/pkg/servregistry"
+	"github.com/CloudNativeSDWAN/cnwan-operator/pkg/servregistry/etcd"
 	opetcd "github.com/CloudNativeSDWAN/cnwan-operator/pkg/servregistry/etcd"
 	"github.com/CloudNativeSDWAN/cnwan-reader/pkg/openapi"
 	"github.com/CloudNativeSDWAN/cnwan-reader/pkg/queue"
@@ -102,8 +106,17 @@ func (e *etcdWatcher) parseEndpointAndCreateEvent(kvpair *mvccpb.KeyValue, event
 
 	srv, err := e.servreg.GetServ(endp.NsName, endp.ServName)
 	if err != nil {
-		l.Err(err).Msg("error while trying to get parent service: skipping endpoint...")
-		return nil, err
+		if errors.Is(err, servregistry.ErrNotFound) {
+			fmt.Println("getting before the delete")
+			// If not found, then we'll try to get the previous version
+			srv, err = e.getServiceBeforeDelete(etcd.KeyFromNames(endp.NsName, endp.ServName).String())
+		}
+
+		// Still an error?
+		if err != nil {
+			l.Err(err).Msg("error while trying to get parent service: skipping endpoint...")
+			return nil, err
+		}
 	}
 
 	if !mapContainsKeys(srv.Metadata, e.options.targetKeys) {
@@ -115,6 +128,32 @@ func (e *etcdWatcher) parseEndpointAndCreateEvent(kvpair *mvccpb.KeyValue, event
 	return event, nil
 }
 
+func (e *etcdWatcher) getServiceBeforeDelete(name string) (*opsr.Service, error) {
+	// First, we need to get the revision (WithPrevKV does not work here)
+	resp, err := e.kv.Get(context.Background(), name, clientv3.WithCountOnly())
+	if err != nil {
+		return nil, fmt.Errorf("error while getting key last revision: %w", err)
+	}
+
+	// Now we get the object with the previous revision
+	resp, err = e.kv.Get(context.Background(), name, clientv3.WithRev(resp.Header.Revision-1))
+	if err != nil {
+		return nil, fmt.Errorf("error while getting service with previous revision: %w", err)
+	}
+
+	if resp.Count == 0 {
+		return nil, servregistry.ErrNotFound
+	}
+
+	var serv opsr.Service
+	if err := yaml.NewDecoder(bytes.NewReader(resp.Kvs[0].Value)).
+		Decode(&serv); err != nil {
+		return nil, fmt.Errorf("could not unmarshal service: %w", err)
+	}
+
+	return &serv, nil
+}
+
 func (e *etcdWatcher) parseEndpointChange(now, prev *mvccpb.KeyValue) (*openapi.Event, error) {
 	l := log.With().Str("key", string(now.Key)).Str("event", "update").Logger()
 	var parsedPrev *opsr.Endpoint
diff --git a/pkg/cmd/watch/etcd/watcher_test.go b/pkg/cmd/watch/etcd/watcher_test.go
index dd33574..f842c32 100644
--- a/pkg/cmd/watch/etcd/watcher_test.go
+++ b/pkg/cmd/watch/etcd/watcher_test.go
@@ -1,4 +1,4 @@
-// Copyright © 2021 Cisco
+// Copyright © 2021, 2022 Cisco
 //
 // SPDX-License-Identifier: Apache-2.0
 //
@@ -210,16 +210,6 @@ func TestParseEndpointAndCreateEvent(t *testing.T) {
 			},
 			expErr: opsr.ErrNsNameNotProvided,
 		},
-		{
-			kv: &mvccpb.KeyValue{
-				Key:   []byte(okEndpKey.String()),
-				Value: okEndpVal,
-			},
-			getServ: func(nsName, servName string) (*opsr.Service, error) {
-				return nil, opsr.ErrNotFound
-			},
-			expErr: opsr.ErrNotFound,
-		},
 		{
 			kv: &mvccpb.KeyValue{
 				Key:   []byte(okEndpKey.String()),