Add rpm virtual repositories (#131)

Virtual repos only merge helm and pypi, so several rpm repos (e.g. many github_rpm remotes) cannot be served as one yum repo.

- merge member primary/filelists/other into one repodata set; member order wins duplicate NEVRAs
- read member repodata through local, github_rpm and proxied remote paths
- prefix package locations (incl. xml:base under a member upstream) with the member name and 302 them to the member route
- reject absolute and dot-segment member paths; escape the redirect and keep its query
- return 502 when any member's repodata is unavailable
- reuse each virtual's merge for 60s behind singleflight; serve data files from its current and previous merge (per replica)
- add merger/engine unit tests and a dockerised dnf e2e case

Reviewed-on: #131
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

e2e-docker/virtual_test.go

@@ -3,9 +3,17 @@
 package e2edocker
 
 import (
+	"bytes"
+	"compress/gzip"
+	"encoding/xml"
+	"fmt"
+	"io"
 	"net/http"
+	"os"
+	"os/exec"
 	"strings"
 	"testing"
+	"time"
 )
 
 // TestVirtualPyPIMerge uploads different packages to two pypi locals and
@@ -52,3 +60,79 @@ func TestVirtualHelmMerge(t *testing.T) {
 		t.Fatalf("merged helm index missing a member chart (want alpha and beta): %s", s)
 	}
 }
+
+// TestVirtualRPMMerge merges a remote rpm repo and a local rpm repo carrying the
+// same package: the first member wins the duplicate, its package download
+// routes through the virtual, and a real dnf can consume the merged repo.
+func TestVirtualRPMMerge(t *testing.T) {
+	createRepo(t, `{"name":"vrpm-remote","package_type":"rpm","repo_type":"remote","base_url":"`+mockUpstream()+`/rpm-mirror","stale_on_error":true}`)
+	createRepo(t, `{"name":"vrpm-local","package_type":"rpm","repo_type":"local"}`)
+	defer deleteRepo(t, "vrpm-remote")
+	defer deleteRepo(t, "vrpm-local")
+
+	pkg := fixtureBytes(t, "rpmrepo/Packages/e2e-testpkg-1.0-1.noarch.rpm")
+	uploadFile(t, "vrpm-local", "e2e-testpkg-1.0-1.noarch.rpm", pkg, "application/x-rpm")
+
+	createVirtual(t, `{"name":"vrpm","package_type":"rpm","members":["vrpm-remote","vrpm-local"]}`)
+	defer deleteVirtual(t, "vrpm")
+
+	resp, body := getEventually(t, api("/api/v1/virtual/vrpm/repodata/repomd.xml"), 15*time.Second)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("virtual repomd.xml: status %d: %s", resp.StatusCode, body)
+	}
+	var md struct {
+		Data []struct {
+			Type     string `xml:"type,attr"`
+			Location struct {
+				Href string `xml:"href,attr"`
+			} `xml:"location"`
+		} `xml:"data"`
+	}
+	if err := xml.Unmarshal(body, &md); err != nil {
+		t.Fatalf("parse repomd.xml: %v\n%s", err, body)
+	}
+	var primary []byte
+	for _, d := range md.Data {
+		if d.Type == "primary" {
+			resp, gz := doRequest(t, http.MethodGet, api("/api/v1/virtual/vrpm/"+d.Location.Href), nil, "")
+			if resp.StatusCode != http.StatusOK {
+				t.Fatalf("primary: status %d", resp.StatusCode)
+			}
+			r, err := gzip.NewReader(bytes.NewReader(gz))
+			if err != nil {
+				t.Fatal(err)
+			}
+			primary, _ = io.ReadAll(r)
+		}
+	}
+	href := "vrpm-remote/Packages/e2e-testpkg-1.0-1.noarch.rpm"
+	if strings.Count(string(primary), "<name>e2e-testpkg</name>") != 1 || !strings.Contains(string(primary), `href="`+href+`"`) {
+		t.Fatalf("merged primary should hold one e2e-testpkg owned by the first member:\n%s", primary)
+	}
+
+	resp, got := doRequest(t, http.MethodGet, api("/api/v1/virtual/vrpm/"+href), nil, "")
+	if resp.StatusCode != http.StatusOK || !bytes.Equal(got, pkg) {
+		t.Fatalf("package via virtual: status %d, %d bytes (want %d)", resp.StatusCode, len(got), len(pkg))
+	}
+
+	network := os.Getenv("COMPOSE_NETWORK")
+	internal := os.Getenv("ARTIFACTAPI_INTERNAL")
+	if network == "" || internal == "" {
+		t.Skip("COMPOSE_NETWORK/ARTIFACTAPI_INTERNAL not set; skipping real dnf")
+	}
+	if _, err := exec.LookPath("docker"); err != nil {
+		t.Skip("docker not available on the test host")
+	}
+	repoConf := fmt.Sprintf("[vrpm]\nname=vrpm\nbaseurl=%s/api/v1/virtual/vrpm/\nenabled=1\ngpgcheck=0\nmetadata_expire=0\n", strings.TrimRight(internal, "/"))
+	script := "set -euo pipefail; " +
+		"printf '%s' \"$REPO\" > /etc/yum.repos.d/vrpm.repo; " +
+		"dnf -y --disablerepo='*' --enablerepo=vrpm makecache; " +
+		"dnf -y --disablerepo='*' --enablerepo=vrpm list --available; " +
+		"dnf -y --disablerepo='*' --enablerepo=vrpm install e2e-testpkg; " +
+		"rpm -q e2e-testpkg"
+	out, err := exec.Command("docker", "run", "--rm", "--network", network, "-e", "REPO="+repoConf,
+		"rockylinux:9", "bash", "-c", script).CombinedOutput()
+	if err != nil {
+		t.Fatalf("real dnf against rpm virtual failed: %v\n%s", err, out)
+	}
+}