Optimize HTTP client creation with caching by timeout

Add sync.Map-based cache for HTTP clients indexed by timeout duration.
This eliminates repeated client allocations during download operations.

Changes:
- httpClientWithTimeout() now caches clients by timeout value
- Use sync.Map for thread-safe caching without lock contention
- Add TestHTTPClientCaching to verify caching behavior

Impact: Reduces allocations during describe --details operations
(4 downloads per command) and all other download workflows.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Joeavaikath

cmd/shared/download.go

@@ -25,6 +25,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"sync"
 	"time"
 
 	nacv1alpha1 "github.com/migtools/oadp-non-admin/api/v1alpha1"
@@ -33,6 +34,11 @@ import (
 	kbclient "sigs.k8s.io/controller-runtime/pkg/client"
 )
 
+var (
+	// Cache HTTP clients by timeout duration
+	httpClientCache sync.Map // map[time.Duration]*http.Client
+)
+
 // DefaultHTTPTimeout is the default timeout for HTTP requests when downloading content from object storage.
 // This prevents the CLI from hanging indefinitely if the connection stalls.
 const DefaultHTTPTimeout = 10 * time.Minute
@@ -69,9 +75,19 @@ func GetHTTPTimeoutWithOverride(override time.Duration) time.Duration {
 // httpClientWithTimeout returns an HTTP client with a configured timeout.
 // Using a custom client instead of http.DefaultClient ensures downloads don't hang indefinitely.
 func httpClientWithTimeout(timeout time.Duration) *http.Client {
-	return &http.Client{
+	// Try to load from cache
+	if cached, ok := httpClientCache.Load(timeout); ok {
+		return cached.(*http.Client)
+	}
+
+	// Create new client
+	client := &http.Client{
 		Timeout: timeout,
 	}
+
+	// Store in cache (LoadOrStore handles race conditions)
+	actual, _ := httpClientCache.LoadOrStore(timeout, client)
+	return actual.(*http.Client)
 }
 
 // DownloadRequestOptions holds configuration for creating and processing NonAdminDownloadRequests

cmd/shared/download_test.go

@@ -147,6 +147,23 @@ func TestHttpClientWithTimeout(t *testing.T) {
 	}
 }
 
+// TestHTTPClientCaching verifies that HTTP clients are cached by timeout duration
+func TestHTTPClientCaching(t *testing.T) {
+	timeout := 10 * time.Minute
+	client1 := httpClientWithTimeout(timeout)
+	client2 := httpClientWithTimeout(timeout)
+
+	if client1 != client2 {
+		t.Error("Expected same client instance for same timeout")
+	}
+
+	differentTimeout := 5 * time.Minute
+	client3 := httpClientWithTimeout(differentTimeout)
+	if client1 == client3 {
+		t.Error("Expected different client for different timeout")
+	}
+}
+
 // TestDownloadContentWithTimeout tests downloading content with explicit timeout
 func TestDownloadContentWithTimeout(t *testing.T) {
 	tests := []struct {