From 8e264cf02811303eecf20ed07861adbea72a91eb Mon Sep 17 00:00:00 2001
From: Brian Picciano <me@mediocregopher.com>
Date: Tue, 5 Nov 2024 11:59:45 +0100
Subject: [PATCH] Rework how Network background jobs are managed a bit

---
 go/daemon/network/network.go | 89 +++++++++++++++++++++---------------
 1 file changed, 51 insertions(+), 38 deletions(-)

diff --git a/go/daemon/network/network.go b/go/daemon/network/network.go
index 1b1dc64..096741b 100644
--- a/go/daemon/network/network.go
+++ b/go/daemon/network/network.go
@@ -23,6 +23,7 @@ import (
 	"sync"
 	"time"
 
+	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
 	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
 	"golang.org/x/exp/maps"
 )
@@ -181,13 +182,15 @@ type network struct {
 	networkConfig daecommon.NetworkConfig
 	currBootstrap bootstrap.Bootstrap
 
-	shutdownCh chan struct{}
-	wg         sync.WaitGroup
+	workerCtx    context.Context
+	workerCancel context.CancelFunc
+	wg           sync.WaitGroup
 }
 
 // instatiateNetwork returns an instantiated *network instance which has not yet
 // been initialized.
 func instatiateNetwork(
+	ctx context.Context,
 	logger *mlog.Logger,
 	networkConfig daecommon.NetworkConfig,
 	envBinDirPath string,
@@ -195,6 +198,8 @@ func instatiateNetwork(
 	runtimeDir toolkit.Dir,
 	opts *Opts,
 ) *network {
+	ctx = context.WithoutCancel(ctx)
+	ctx, cancel := context.WithCancel(ctx)
 	return &network{
 		logger:        logger,
 		networkConfig: networkConfig,
@@ -202,7 +207,8 @@ func instatiateNetwork(
 		stateDir:      stateDir,
 		runtimeDir:    runtimeDir,
 		opts:          opts.withDefaults(),
-		shutdownCh:    make(chan struct{}),
+		workerCtx:     ctx,
+		workerCancel:  cancel,
 	}
 }
 
@@ -244,6 +250,7 @@ func Load(
 	Network, error,
 ) {
 	n := instatiateNetwork(
+		ctx,
 		logger,
 		networkConfig,
 		envBinDirPath,
@@ -289,6 +296,7 @@ func Join(
 	Network, error,
 ) {
 	n := instatiateNetwork(
+		ctx,
 		logger,
 		networkConfig,
 		envBinDirPath,
@@ -355,6 +363,7 @@ func Create(
 	garageRPCSecret := toolkit.RandStr(32)
 
 	n := instatiateNetwork(
+		ctx,
 		logger,
 		networkConfig,
 		envBinDirPath,
@@ -407,6 +416,38 @@ func (n *network) initializeDirs(mayExist bool) error {
 	return nil
 }
 
+func (n *network) periodically(
+	logger *mlog.Logger,
+	fn func(context.Context) error,
+	period time.Duration,
+) {
+	n.wg.Add(1)
+	go func() {
+		defer n.wg.Done()
+
+		ctx := mctx.Annotate(n.workerCtx, "period", period)
+
+		ticker := time.NewTicker(period)
+		defer ticker.Stop()
+
+		logger.Info(ctx, "Starting background job runner")
+		defer logger.Info(ctx, "Stopping background job runner")
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+
+			case <-ticker.C:
+				logger.Info(ctx, "Background job running")
+				if err := fn(ctx); err != nil {
+					logger.Error(ctx, "Background job failed", err)
+				}
+			}
+		}
+	}()
+}
+
 func (n *network) initialize(
 	ctx context.Context, prevBootstrap bootstrap.Bootstrap,
 ) error {
@@ -463,21 +504,11 @@ func (n *network) initialize(
 		return fmt.Errorf("Reloading network bootstrap: %w", err)
 	}
 
-	ctx = context.WithoutCancel(ctx)
-	ctx, cancel := context.WithCancel(ctx)
-	n.wg.Add(1)
-	go func() {
-		defer n.wg.Done()
-		<-n.shutdownCh
-		cancel()
-	}()
-
-	n.wg.Add(1)
-	go func() {
-		defer n.wg.Done()
-		n.reloadLoop(ctx)
-		n.logger.Debug(ctx, "Daemon reload loop stopped")
-	}()
+	n.periodically(
+		n.logger.WithNamespace("reloadHosts"),
+		n.reloadHosts,
+		3*time.Minute,
+	)
 
 	return nil
 }
@@ -575,25 +606,6 @@ func (n *network) reloadHosts(ctx context.Context) error {
 	return nil
 }
 
-func (n *network) reloadLoop(ctx context.Context) {
-	const period = 3 * time.Minute
-	ticker := time.NewTicker(period)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ctx.Done():
-			return
-
-		case <-ticker.C:
-			if err := n.reloadHosts(ctx); err != nil {
-				n.logger.Error(ctx, "Attempting to reload", err)
-				continue
-			}
-		}
-	}
-}
-
 // returns the bootstrap prior to the reload being applied.
 func (n *network) reload(
 	ctx context.Context,
@@ -966,10 +978,11 @@ func (n *network) GetNetworkCreationParams(
 }
 
 func (n *network) Shutdown() error {
-	close(n.shutdownCh)
+	n.workerCancel()
 	n.wg.Wait()
 
 	if n.children != nil {
+		n.logger.Info(context.Background(), "Shutting down children")
 		n.children.Shutdown()
 	}