From 55edeed22b8bfe1e71d68b5c75cf434f5be647b6 Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Thu, 23 May 2024 17:25:45 -0700
Subject: [PATCH] allow controlling detected platforms cache timeout

Because detecting emulator changes can be relatively
expensive, avoid doing it very frequently. A new config
parameter allows controlling if users prefer more or
less frequent updates or want to disable detecting
changes completely and only rely on emultor configuration
at boot time.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 cmd/buildkitd/config/config.go |  8 ++++++++
 cmd/buildkitd/main.go          |  6 ++++++
 util/archutil/detect.go        | 13 ++++++++++---
 worker/base/worker.go          |  8 ++++++--
 4 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/cmd/buildkitd/config/config.go b/cmd/buildkitd/config/config.go
index 28c11acb983ed..d8da19ecafec3 100644
--- a/cmd/buildkitd/config/config.go
+++ b/cmd/buildkitd/config/config.go
@@ -38,6 +38,14 @@ type Config struct {
 		Dockerfile DockerfileFrontendConfig `toml:"dockerfile.v0"`
 		Gateway    GatewayFrontendConfig    `toml:"gateway.v0"`
 	} `toml:"frontend"`
+
+	System *SystemConfig `toml:"system"`
+}
+
+type SystemConfig struct {
+	// PlatformCacheMaxAge controls how often supported platforms
+	// are refreshed by rescanning the system.
+	PlatformsCacheMaxAge *Duration `toml:"platformsCacheMaxAge"`
 }
 
 type LogConfig struct {
diff --git a/cmd/buildkitd/main.go b/cmd/buildkitd/main.go
index d254b7ce1d959..d57defa53826e 100644
--- a/cmd/buildkitd/main.go
+++ b/cmd/buildkitd/main.go
@@ -262,6 +262,12 @@ func main() {
 			logrus.SetLevel(logrus.TraceLevel)
 		}
 
+		if sc := cfg.System; sc != nil {
+			if v := sc.PlatformsCacheMaxAge; v != nil {
+				archutil.CacheMaxAge = v.Duration
+			}
+		}
+
 		if cfg.GRPC.DebugAddress != "" {
 			if err := setupDebugHandlers(cfg.GRPC.DebugAddress); err != nil {
 				return err
diff --git a/util/archutil/detect.go b/util/archutil/detect.go
index 5808333f91b5f..b52a77adee09f 100644
--- a/util/archutil/detect.go
+++ b/util/archutil/detect.go
@@ -4,21 +4,28 @@ import (
 	"sort"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/containerd/containerd/platforms"
 	"github.com/moby/buildkit/util/bklog"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-var mu sync.Mutex
-var arr []ocispecs.Platform
+var CacheMaxAge time.Duration = 20 * time.Second
+
+var (
+	mu          sync.Mutex
+	arr         []ocispecs.Platform
+	lastRefresh time.Time
+)
 
 func SupportedPlatforms(noCache bool) []ocispecs.Platform {
 	mu.Lock()
 	defer mu.Unlock()
-	if !noCache && arr != nil {
+	if arr != nil && (!noCache || CacheMaxAge < 0 || time.Since(lastRefresh) < CacheMaxAge) {
 		return arr
 	}
+	defer func() { lastRefresh = time.Now() }()
 	def := nativePlatform()
 	arr = append([]ocispecs.Platform{}, def)
 
diff --git a/worker/base/worker.go b/worker/base/worker.go
index de8c1d5774732..78cd6fef85c8a 100644
--- a/worker/base/worker.go
+++ b/worker/base/worker.go
@@ -245,10 +245,14 @@ func (w *Worker) Labels() map[string]string {
 
 func (w *Worker) Platforms(noCache bool) []ocispecs.Platform {
 	if noCache {
+		matchers := make([]platforms.MatchComparer, len(w.WorkerOpt.Platforms))
+		for i, p := range w.WorkerOpt.Platforms {
+			matchers[i] = platforms.Only(p)
+		}
 		for _, p := range archutil.SupportedPlatforms(noCache) {
 			exists := false
-			for _, pp := range w.WorkerOpt.Platforms {
-				if platforms.Only(pp).Match(p) {
+			for _, m := range matchers {
+				if m.Match(p) {
 					exists = true
 					break
 				}