Reuse http client on storage resolver (#1147)

Reuses http client on storage resolves and sets a generous connect timeout
to circuit-break on network issues.

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Add support for multi-platform container images. [#1162](https://github.com/elastic/package-registry/pull/1162)
 * Use Wolfi as base for container images. [#1169](https://github.com/elastic/package-registry/pull/1169)
+* Reuse HTTP client when proxifying resolver requests. [#1147](https://github.com/elastic/package-registry/pull/1147)
 
 ### Deprecated
 

storage/indexer.go

@@ -8,6 +8,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
+	"net/http"
 	"net/url"
 	"strings"
 	"sync"
@@ -100,7 +102,17 @@ func (i *Indexer) setupResolver() error {
 		return err
 	}
 
+	httpClient := http.Client{
+		Transport: &http.Transport{
+			DialContext: (&net.Dialer{
+				// Connect timeout.
+				Timeout: 20 * time.Second,
+			}).DialContext,
+		},
+	}
+
 	i.resolver = storageResolver{
+		client:               &httpClient,
 		artifactsPackagesURL: *baseURL.ResolveReference(&url.URL{Path: artifactsPackagesStoragePath + "/"}),
 		artifactsStaticURL:   *baseURL.ResolveReference(&url.URL{Path: artifactsStaticStoragePath + "/"}),
 	}

storage/resolver.go

@@ -14,6 +14,7 @@ import (
 )
 
 type storageResolver struct {
+	client               *http.Client
 	artifactsPackagesURL url.URL
 	artifactsStaticURL   url.URL
 }
@@ -26,15 +27,13 @@ var acceptedHeaders = map[string]string{
 }
 
 func (resolver storageResolver) pipeRequestProxy(w http.ResponseWriter, r *http.Request, remoteURL string) {
-	client := &http.Client{}
-
 	forwardRequest, err := http.NewRequestWithContext(r.Context(), r.Method, remoteURL, nil)
 	if err != nil {
 		http.Error(w, "failed to create request for the package-storage", http.StatusInternalServerError)
 		return
 	}
 
-	resp, err := client.Do(forwardRequest)
+	resp, err := resolver.client.Do(forwardRequest)
 	if err != nil {
 		http.Error(w, "error from package-storage server", http.StatusInternalServerError)
 		return