From 9f9dd2404281e3cf09d76076e20d9f88455cbbc9 Mon Sep 17 00:00:00 2001
From: Jakub Sztandera <kubuxu@protonmail.ch>
Date: Mon, 3 Jun 2019 23:14:41 +0200
Subject: [PATCH] feat: cache interface addresses for 1 minute

This can be quite an overhead in cases of high connection rates.
The main overhead is thread blocking syscall causing a lot of context
switching.

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>
---
 swarm.go      |  5 +++++
 swarm_addr.go | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/swarm.go b/swarm.go
index b14e9cf..642faea 100644
--- a/swarm.go
+++ b/swarm.go
@@ -20,6 +20,7 @@ import (
 	goprocessctx "github.com/jbenet/goprocess/context"
 
 	filter "github.com/libp2p/go-maddr-filter"
+	ma "github.com/multiformats/go-multiaddr"
 	mafilter "github.com/whyrusleeping/multiaddr-filter"
 )
 
@@ -58,6 +59,10 @@ type Swarm struct {
 
 	listeners struct {
 		sync.RWMutex
+
+		ifaceAddresses []ma.Multiaddr
+		cacheEOL       time.Time
+
 		m map[transport.Listener]struct{}
 	}
 
diff --git a/swarm_addr.go b/swarm_addr.go
index c86d58b..10179fa 100644
--- a/swarm_addr.go
+++ b/swarm_addr.go
@@ -1,6 +1,8 @@
 package swarm
 
 import (
+	"time"
+
 	addrutil "github.com/libp2p/go-addr-util"
 	ma "github.com/multiformats/go-multiaddr"
 )
@@ -9,6 +11,10 @@ import (
 func (s *Swarm) ListenAddresses() []ma.Multiaddr {
 	s.listeners.RLock()
 	defer s.listeners.RUnlock()
+	return s.listenAddressesNoLock()
+}
+
+func (s *Swarm) listenAddressesNoLock() []ma.Multiaddr {
 	addrs := make([]ma.Multiaddr, 0, len(s.listeners.m))
 	for l := range s.listeners.m {
 		addrs = append(addrs, l.Multiaddr())
@@ -16,9 +22,47 @@ func (s *Swarm) ListenAddresses() []ma.Multiaddr {
 	return addrs
 }
 
+const ifaceAddrsCacheDuration = 1 * time.Minute
+
 // InterfaceListenAddresses returns a list of addresses at which this swarm
 // listens. It expands "any interface" addresses (/ip4/0.0.0.0, /ip6/::) to
 // use the known local interfaces.
 func (s *Swarm) InterfaceListenAddresses() ([]ma.Multiaddr, error) {
-	return addrutil.ResolveUnspecifiedAddresses(s.ListenAddresses(), nil)
+	s.listeners.RLock() // RLock start
+	listenAddrs := s.listenAddressesNoLock()
+
+	ifaceAddrs := s.listeners.ifaceAddresses
+	isEOL := time.Now().After(s.listeners.cacheEOL)
+	s.listeners.RUnlock() // RLock end
+
+	if listenAddrs != nil && !isEOL {
+		// Cache is valid
+		return addrutil.ResolveUnspecifiedAddresses(listenAddrs, ifaceAddrs)
+	}
+
+	// Cache is not valid
+	// Perfrom double checked locking
+
+	s.listeners.Lock() // Lock start
+
+	listenAddrs = s.listenAddressesNoLock()
+
+	ifaceAddrs = s.listeners.ifaceAddresses
+	isEOL = time.Now().After(s.listeners.cacheEOL)
+	if listenAddrs == nil || isEOL {
+		// Cache is still invalid
+		var err error
+		ifaceAddrs, err = addrutil.InterfaceAddresses()
+		if err != nil {
+			s.listeners.Unlock() // Lock early exit
+			return nil, err
+		}
+
+		s.listeners.ifaceAddresses = ifaceAddrs
+		s.listeners.cacheEOL = time.Now().Add(ifaceAddrsCacheDuration)
+	}
+
+	s.listeners.Unlock() // Lock end
+
+	return addrutil.ResolveUnspecifiedAddresses(listenAddrs, ifaceAddrs)
 }
-- 
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