Remove quit chan from Manager.

Make the main loop of the Manager a blocking func which accepts a
context. Shutdown the Manager when the context is canceled.

This slightly alters the semantics of the code but in a way that has
functionally no impact. Previously the Tickers which update the Manager
would only be stopped after the HTTP server and creeper had stopped, but
now they are stopped immediately when the context is canceled.

decred.go

@@ -159,6 +159,14 @@ func main() {
 	amgr.AddAddresses([]netip.AddrPort{seeder})
 
 	var wg sync.WaitGroup
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		amgr.run(ctx) // only returns on context cancellation
+		log.Print("Address manager done.")
+	}()
+
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
@@ -177,6 +185,5 @@ func main() {
 
 	// Wait for crawler and http server, then stop address manager.
 	wg.Wait()
-	amgr.Stop()
 	log.Print("Bye!")
 }

manager.go

@@ -1,10 +1,11 @@
-// Copyright (c) 2018-2021 The Decred developers
+// Copyright (c) 2018-2023 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
 package main
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -34,8 +35,6 @@ type Manager struct {
 	mtx sync.RWMutex
 
 	nodes     map[string]*Node
-	wg        sync.WaitGroup
-	quit      chan struct{}
 	peersFile string
 }
 
@@ -72,7 +71,6 @@ func NewManager(dataDir string) (*Manager, error) {
 	amgr := Manager{
 		nodes:     make(map[string]*Node),
 		peersFile: filepath.Join(dataDir, peersFilename),
-		quit:      make(chan struct{}),
 	}
 
 	err = amgr.deserializePeers()
@@ -86,18 +84,9 @@ func NewManager(dataDir string) (*Manager, error) {
 		}
 	}
 
-	amgr.wg.Add(1)
-	go amgr.addressHandler()
-
 	return &amgr, nil
 }
 
-func (m *Manager) Stop() {
-	close(m.quit)
-	m.wg.Wait() // wait for addressHandler
-	log.Print("Address manager done.")
-}
-
 func (m *Manager) AddAddresses(addrPorts []netip.AddrPort) int {
 	var count int
 
@@ -239,10 +228,8 @@ func (m *Manager) Good(addrPort netip.AddrPort, services wire.ServiceFlag, pver
 	m.mtx.Unlock()
 }
 
-// addressHandler is the main handler for the address manager.  It must be run
-// as a goroutine.
-func (m *Manager) addressHandler() {
-	defer m.wg.Done()
+// run is the main handler for the address manager.
+func (m *Manager) run(ctx context.Context) {
 	pruneAddressTicker := time.NewTicker(pruneAddressInterval)
 	defer pruneAddressTicker.Stop()
 	dumpAddressTicker := time.NewTicker(dumpAddressInterval)
@@ -254,7 +241,7 @@ out:
 			m.savePeers()
 		case <-pruneAddressTicker.C:
 			m.prunePeers()
-		case <-m.quit:
+		case <-ctx.Done():
 			break out
 		}
 	}