From 1cb3251b500ed14ac3504fdd72578bfc9a4b1348 Mon Sep 17 00:00:00 2001
From: "mergify[bot]" <37929162+mergify[bot]@users.noreply.github.com>
Date: Wed, 7 Jul 2021 16:48:49 +0000
Subject: [PATCH] Policy changes can be dropped during policy rollouts to large
 number of agents.  Aggregates changes to avoid missing updates. (#525)

(cherry picked from commit 1fc4b1f758c68858071568267f567c952ffe189e)

Co-authored-by: Sean Cunningham <sean.cunningham@elastic.co>
---
 cmd/fleet/server.go                          |  3 +-
 internal/pkg/monitor/subscription_monitor.go |  9 ++--
 internal/pkg/policy/monitor.go               | 44 +++++++++++++++++++-
 3 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/cmd/fleet/server.go b/cmd/fleet/server.go
index 22a596f42..bb9960889 100644
--- a/cmd/fleet/server.go
+++ b/cmd/fleet/server.go
@@ -12,6 +12,7 @@ import (
 	"net/http"
 
 	"github.com/elastic/fleet-server/v7/internal/pkg/config"
+	"github.com/elastic/fleet-server/v7/internal/pkg/logger"
 
 	"github.com/elastic/beats/v7/libbeat/common/transport/tlscommon"
 	"github.com/julienschmidt/httprouter"
@@ -142,7 +143,7 @@ type stubLogger struct {
 }
 
 func (s *stubLogger) Write(p []byte) (n int, err error) {
-	log.Error().Bytes("msg", p).Send()
+	log.Error().Bytes(logger.EcsMessage, p).Send()
 	return len(p), nil
 }
 
diff --git a/internal/pkg/monitor/subscription_monitor.go b/internal/pkg/monitor/subscription_monitor.go
index ec5c71821..02e43c4d8 100644
--- a/internal/pkg/monitor/subscription_monitor.go
+++ b/internal/pkg/monitor/subscription_monitor.go
@@ -145,10 +145,11 @@ func (m *monitorT) notify(ctx context.Context, hits []es.HitT) {
 				select {
 				case s.c <- hits:
 				case <-lc.Done():
-					err := ctx.Err()
-					if err == context.DeadlineExceeded {
-						log.Err(err).Str("ctx", "subscription monitor").Dur("timeout", m.subTimeout).Msg("dropped notification")
-					}
+					log.Error().
+						Err(lc.Err()).
+						Str("ctx", "subscription monitor").
+						Dur("timeout", m.subTimeout).
+						Msg("dropped notification")
 				}
 			}(s)
 		}
diff --git a/internal/pkg/policy/monitor.go b/internal/pkg/policy/monitor.go
index 49befe528..598acc849 100644
--- a/internal/pkg/policy/monitor.go
+++ b/internal/pkg/policy/monitor.go
@@ -101,6 +101,13 @@ func (m *monitorT) Run(ctx context.Context) error {
 	s := m.monitor.Subscribe()
 	defer m.monitor.Unsubscribe(s)
 
+	// The output from m.monitor times out if we don't pull data off quickly enough.
+	// Rollout can take a while; append upates here until we can attend to it.
+	// TODO: This is a workaround for 7.14.  Rollout strategy will be reconsidered for 7.15.
+	subCtx, cfunc := context.WithCancel(ctx)
+	defer cfunc()
+	outputCh := m.monitorOutputChannel(subCtx, s.Output())
+
 	close(m.startCh)
 LOOP:
 	for {
@@ -111,7 +118,7 @@ LOOP:
 			if err := m.process(ctx); err != nil {
 				return err
 			}
-		case hits := <-s.Output():
+		case hits := <-outputCh:
 			policies := make([]model.Policy, len(hits))
 			for i, hit := range hits {
 				err := hit.Unmarshal(&policies[i])
@@ -128,6 +135,35 @@ LOOP:
 	return nil
 }
 
+// Aggegates changes from the output channel until the main loop can process.
+func (m *monitorT) monitorOutputChannel(ctx context.Context, outputCh <-chan []es.HitT) chan []es.HitT {
+	localOutputCh := make(chan []es.HitT)
+
+	go func() {
+
+		var hits []es.HitT
+		var outCh chan []es.HitT
+
+		for {
+			select {
+			case <-ctx.Done():
+				m.log.Info().Msg("Exit policy monitor local")
+				return
+			case nHits := <-outputCh:
+				m.log.Info().Int("nHits", len(nHits)).Msg("Received hits on local monitor")
+				hits = append(hits, nHits...)
+				outCh = localOutputCh
+			case outCh <- hits:
+				m.log.Info().Int("nHits", len(hits)).Msg("Hits dispatched to main loop")
+				outCh = nil
+				hits = nil
+			}
+		}
+	}()
+
+	return localOutputCh
+}
+
 func (m *monitorT) waitStart(ctx context.Context) (err error) {
 	select {
 	case <-ctx.Done():
@@ -189,7 +225,11 @@ func (m *monitorT) groupByLatest(policies []model.Policy) map[string]model.Polic
 }
 
 func (m *monitorT) rollout(ctx context.Context, policy model.Policy) error {
-	zlog := m.log.With().Str("policyId", policy.PolicyId).Logger()
+	zlog := m.log.With().
+		Str("policyId", policy.PolicyId).
+		Int64("revisionIdx", policy.RevisionIdx).
+		Int64("coordinatorIdx", policy.CoordinatorIdx).
+		Logger()
 
 	pp, err := NewParsedPolicy(policy)
 	if err != nil {