Add dendrite-upgrade-test (#1901)

* Add WIP binary for testing dendrite version upgrades

* WIP dendrite upgrade work

* Finish dendrite upgrade checks

* go mod tidy

* Review comments; print container logs on failure

* Linting

3 files changed, 679 insertions, 0 deletions

diff --git a/cmd/dendrite-upgrade-tests/main.go b/cmd/dendrite-upgrade-tests/main.go
new file mode 100644
index 00000000..2c3fcf51
--- /dev/null
+++ b/cmd/dendrite-upgrade-tests/main.go
@@ -0,0 +1,430 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Masterminds/semver/v3"
+	"github.com/codeclysm/extract"
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/api/types/mount"
+	"github.com/docker/docker/api/types/volume"
+	"github.com/docker/docker/client"
+	"github.com/docker/go-connections/nat"
+)
+
+var (
+	flagTempDir          = flag.String("tmp", "tmp", "Path to temporary directory to dump tarballs to")
+	flagFrom             = flag.String("from", "0.1.0", "The version to start from e.g '0.3.1'.")
+	flagTo               = flag.String("to", "HEAD", "The version to end on e.g '0.3.3'.")
+	flagBuildConcurrency = flag.Int("build-concurrency", runtime.NumCPU(), "The amount of build concurrency when building images")
+	alphaNumerics        = regexp.MustCompile("[^a-zA-Z0-9]+")
+)
+
+// Embed the Dockerfile to use when building dendrite versions.
+// We cannot use the dockerfile associated with the repo with each version sadly due to changes in
+// Docker versions. Specifically, earlier Dendrite versions are incompatible with newer Docker clients
+// due to the error:
+//   When using COPY with more than one source file, the destination must be a directory and end with a /
+// We need to run a postgres anyway, so use the dockerfile associated with Complement instead.
+const Dockerfile = `FROM golang:1.13-stretch as build
+RUN apt-get update && apt-get install -y postgresql
+WORKDIR /build
+
+# Copy the build context to the repo as this is the right dendrite code. This is different to the
+# Complement Dockerfile which wgets a branch.
+COPY . .
+
+RUN go build ./cmd/dendrite-monolith-server
+RUN go build ./cmd/generate-keys
+RUN go build ./cmd/generate-config
+RUN ./generate-config --ci > dendrite.yaml
+RUN ./generate-keys --private-key matrix_key.pem --tls-cert server.crt --tls-key server.key
+
+# Replace the connection string with a single postgres DB, using user/db = 'postgres' and no password
+RUN sed -i "s%connection_string:.*$%connection_string: postgresql://postgres@localhost/postgres?sslmode=disable%g" dendrite.yaml 
+# No password when connecting over localhost
+RUN sed -i "s%127.0.0.1/32            md5%127.0.0.1/32            trust%g" /etc/postgresql/9.6/main/pg_hba.conf
+# Bump up max conns for moar concurrency
+RUN sed -i 's/max_connections = 100/max_connections = 2000/g' /etc/postgresql/9.6/main/postgresql.conf
+RUN sed -i 's/max_open_conns:.*$/max_open_conns: 100/g' dendrite.yaml
+
+# This entry script starts postgres, waits for it to be up then starts dendrite
+RUN echo '\
+#!/bin/bash -eu \n\
+pg_lsclusters \n\
+pg_ctlcluster 9.6 main start \n\
+ \n\
+until pg_isready \n\
+do \n\
+  echo "Waiting for postgres"; \n\
+  sleep 1; \n\
+done \n\
+ \n\
+sed -i "s/server_name: localhost/server_name: ${SERVER_NAME}/g" dendrite.yaml \n\
+./dendrite-monolith-server --tls-cert server.crt --tls-key server.key --config dendrite.yaml \n\
+' > run_dendrite.sh && chmod +x run_dendrite.sh
+
+ENV SERVER_NAME=localhost
+EXPOSE 8008 8448
+CMD /build/run_dendrite.sh `
+
+// downloadArchive downloads an arbitrary github archive of the form:
+//   https://github.com/matrix-org/dendrite/archive/v0.3.11.tar.gz
+// and re-tarballs it without the top-level directory which contains branch information. It inserts
+// the contents of `dockerfile` as a root file `Dockerfile` in the re-tarballed directory such that
+// you can directly feed the retarballed archive to `ImageBuild` to have it run said dockerfile.
+// Returns the tarball buffer on success.
+func downloadArchive(cli *http.Client, tmpDir, archiveURL string, dockerfile []byte) (*bytes.Buffer, error) {
+	resp, err := cli.Get(archiveURL)
+	if err != nil {
+		return nil, err
+	}
+	// nolint:errcheck
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("got HTTP %d", resp.StatusCode)
+	}
+	if err = os.Mkdir(tmpDir, os.ModePerm); err != nil {
+		return nil, fmt.Errorf("failed to make temporary directory: %s", err)
+	}
+	// nolint:errcheck
+	defer os.RemoveAll(tmpDir)
+	// dump the tarball temporarily, stripping the top-level directory
+	err = extract.Archive(context.Background(), resp.Body, tmpDir, func(inPath string) string {
+		// remove top level
+		segments := strings.Split(inPath, "/")
+		return strings.Join(segments[1:], "/")
+	})
+	if err != nil {
+		return nil, err
+	}
+	// add top level Dockerfile
+	err = ioutil.WriteFile(path.Join(tmpDir, "Dockerfile"), dockerfile, os.ModePerm)
+	if err != nil {
+		return nil, fmt.Errorf("failed to inject /Dockerfile: %w", err)
+	}
+	// now re-tarball it :/
+	var tarball bytes.Buffer
+	err = compress(tmpDir, &tarball)
+	if err != nil {
+		return nil, err
+	}
+	return &tarball, nil
+}
+
+// buildDendrite builds Dendrite on the branchOrTagName given. Returns the image ID or an error
+func buildDendrite(httpClient *http.Client, dockerClient *client.Client, tmpDir, branchOrTagName string) (string, error) {
+	log.Printf("%s: Downloading version %s to %s\n", branchOrTagName, branchOrTagName, tmpDir)
+	// pull an archive, this contains a top-level directory which screws with the build context
+	// which we need to fix up post download
+	u := fmt.Sprintf("https://github.com/matrix-org/dendrite/archive/%s.tar.gz", branchOrTagName)
+	tarball, err := downloadArchive(httpClient, tmpDir, u, []byte(Dockerfile))
+	if err != nil {
+		return "", fmt.Errorf("failed to download archive %s: %w", u, err)
+	}
+	log.Printf("%s: %s => %d bytes\n", branchOrTagName, u, tarball.Len())
+	log.Printf("%s: Building version %s\n", branchOrTagName, branchOrTagName)
+	res, err := dockerClient.ImageBuild(context.Background(), tarball, types.ImageBuildOptions{
+		Tags: []string{"dendrite-upgrade"},
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to start building image: %s", err)
+	}
+	// nolint:errcheck
+	defer res.Body.Close()
+	decoder := json.NewDecoder(res.Body)
+	// {"aux":{"ID":"sha256:247082c717963bc2639fc2daed08838d67811ea12356cd4fda43e1ffef94f2eb"}}
+	var imageID string
+	for decoder.More() {
+		var dl struct {
+			Stream string                 `json:"stream"`
+			Aux    map[string]interface{} `json:"aux"`
+		}
+		if err := decoder.Decode(&dl); err != nil {
+			return "", fmt.Errorf("failed to decode build image output line: %w", err)
+		}
+		log.Printf("%s: %s", branchOrTagName, dl.Stream)
+		if dl.Aux != nil {
+			imgID, ok := dl.Aux["ID"]
+			if ok {
+				imageID = imgID.(string)
+			}
+		}
+	}
+	return imageID, nil
+}
+
+func getAndSortVersionsFromGithub(httpClient *http.Client) (semVers []*semver.Version, err error) {
+	u := "https://api.github.com/repos/matrix-org/dendrite/tags"
+	res, err := httpClient.Get(u)
+	if err != nil {
+		return nil, err
+	}
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("%s returned HTTP %d", u, res.StatusCode)
+	}
+	resp := []struct {
+		Name string `json:"name"`
+	}{}
+	if err = json.NewDecoder(res.Body).Decode(&resp); err != nil {
+		return nil, err
+	}
+	for _, r := range resp {
+		v, err := semver.NewVersion(r.Name)
+		if err != nil {
+			continue // not a semver, that's ok and isn't an error, we allow tags that aren't semvers
+		}
+		semVers = append(semVers, v)
+	}
+	sort.Sort(semver.Collection(semVers))
+	return semVers, nil
+}
+
+func calculateVersions(cli *http.Client, from, to string) []string {
+	semvers, err := getAndSortVersionsFromGithub(cli)
+	if err != nil {
+		log.Fatalf("failed to collect semvers from github: %s", err)
+	}
+	// snip the lower bound depending on --from
+	if from != "" {
+		fromVer, err := semver.NewVersion(from)
+		if err != nil {
+			log.Fatalf("invalid --from: %s", err)
+		}
+		i := 0
+		for i = 0; i < len(semvers); i++ {
+			if semvers[i].LessThan(fromVer) {
+				continue
+			}
+			break
+		}
+		semvers = semvers[i:]
+	}
+	if to != "" && to != "HEAD" {
+		toVer, err := semver.NewVersion(to)
+		if err != nil {
+			log.Fatalf("invalid --to: %s", err)
+		}
+		var i int
+		for i = len(semvers) - 1; i >= 0; i-- {
+			if semvers[i].GreaterThan(toVer) {
+				continue
+			}
+			break
+		}
+		semvers = semvers[:i+1]
+	}
+	var versions []string
+	for _, sv := range semvers {
+		versions = append(versions, sv.Original())
+	}
+	if to == "HEAD" {
+		versions = append(versions, "HEAD")
+	}
+	return versions
+}
+
+func buildDendriteImages(httpClient *http.Client, dockerClient *client.Client, baseTempDir string, concurrency int, branchOrTagNames []string) map[string]string {
+	// concurrently build all versions, this can be done in any order. The mutex protects the map
+	branchToImageID := make(map[string]string)
+	var mu sync.Mutex
+
+	var wg sync.WaitGroup
+	wg.Add(concurrency)
+	ch := make(chan string, len(branchOrTagNames))
+	for _, branchName := range branchOrTagNames {
+		ch <- branchName
+	}
+	close(ch)
+
+	for i := 0; i < concurrency; i++ {
+		go func() {
+			defer wg.Done()
+			for branchName := range ch {
+				tmpDir := baseTempDir + alphaNumerics.ReplaceAllString(branchName, "")
+				imgID, err := buildDendrite(httpClient, dockerClient, tmpDir, branchName)
+				if err != nil {
+					log.Fatalf("%s: failed to build dendrite image: %s", branchName, err)
+				}
+				mu.Lock()
+				branchToImageID[branchName] = imgID
+				mu.Unlock()
+			}
+		}()
+	}
+	wg.Wait()
+	return branchToImageID
+}
+
+func runImage(dockerClient *client.Client, volumeName, version, imageID string) (csAPIURL, containerID string, err error) {
+	log.Printf("%s: running image %s\n", version, imageID)
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Minute)
+	defer cancel()
+	body, err := dockerClient.ContainerCreate(ctx, &container.Config{
+		Image: imageID,
+		Env:   []string{"SERVER_NAME=hs1"},
+	}, &container.HostConfig{
+		PublishAllPorts: true,
+		Mounts: []mount.Mount{
+			{
+				Type:   mount.TypeVolume,
+				Source: volumeName,
+				Target: "/var/lib/postgresql/9.6/main",
+			},
+		},
+	}, nil, nil, "dendrite_upgrade_test_"+version)
+	if err != nil {
+		return "", "", fmt.Errorf("failed to ContainerCreate: %s", err)
+	}
+	containerID = body.ID
+
+	err = dockerClient.ContainerStart(ctx, containerID, types.ContainerStartOptions{})
+	if err != nil {
+		return "", "", fmt.Errorf("failed to ContainerStart: %s", err)
+	}
+	inspect, err := dockerClient.ContainerInspect(ctx, containerID)
+	if err != nil {
+		return "", "", err
+	}
+	csapiPortInfo, ok := inspect.NetworkSettings.Ports[nat.Port("8008/tcp")]
+	if !ok {
+		return "", "", fmt.Errorf("port 8008 not exposed - exposed ports: %v", inspect.NetworkSettings.Ports)
+	}
+	baseURL := fmt.Sprintf("http://localhost:%s", csapiPortInfo[0].HostPort)
+	versionsURL := fmt.Sprintf("%s/_matrix/client/versions", baseURL)
+	// hit /versions to check it is up
+	var lastErr error
+	for i := 0; i < 500; i++ {
+		res, err := http.Get(versionsURL)
+		if err != nil {
+			lastErr = fmt.Errorf("GET %s => error: %s", versionsURL, err)
+			time.Sleep(50 * time.Millisecond)
+			continue
+		}
+		if res.StatusCode != 200 {
+			lastErr = fmt.Errorf("GET %s => HTTP %s", versionsURL, res.Status)
+			time.Sleep(50 * time.Millisecond)
+			continue
+		}
+		lastErr = nil
+		break
+	}
+	if lastErr != nil {
+		logs, err := dockerClient.ContainerLogs(context.Background(), containerID, types.ContainerLogsOptions{
+			ShowStdout: true,
+			ShowStderr: true,
+		})
+		// ignore errors when cannot get logs, it's just for debugging anyways
+		if err == nil {
+			logbody, err := ioutil.ReadAll(logs)
+			if err == nil {
+				log.Printf("Container logs:\n\n%s\n\n", string(logbody))
+			}
+		}
+	}
+	return baseURL, containerID, lastErr
+}
+
+func destroyContainer(dockerClient *client.Client, containerID string) {
+	err := dockerClient.ContainerRemove(context.TODO(), containerID, types.ContainerRemoveOptions{
+		Force: true,
+	})
+	if err != nil {
+		log.Printf("failed to remove container %s : %s", containerID, err)
+	}
+}
+
+func loadAndRunTests(dockerClient *client.Client, volumeName, v string, branchToImageID map[string]string) error {
+	csAPIURL, containerID, err := runImage(dockerClient, volumeName, v, branchToImageID[v])
+	if err != nil {
+		return fmt.Errorf("failed to run container for branch %v: %v", v, err)
+	}
+	defer destroyContainer(dockerClient, containerID)
+	log.Printf("URL %s -> %s \n", csAPIURL, containerID)
+	if err = runTests(csAPIURL, v); err != nil {
+		return fmt.Errorf("failed to run tests on version %s: %s", v, err)
+	}
+	return nil
+}
+
+func verifyTests(dockerClient *client.Client, volumeName string, versions []string, branchToImageID map[string]string) error {
+	lastVer := versions[len(versions)-1]
+	csAPIURL, containerID, err := runImage(dockerClient, volumeName, lastVer, branchToImageID[lastVer])
+	if err != nil {
+		return fmt.Errorf("failed to run container for branch %v: %v", lastVer, err)
+	}
+	defer destroyContainer(dockerClient, containerID)
+	return verifyTestsRan(csAPIURL, versions)
+}
+
+func main() {
+	flag.Parse()
+	httpClient := &http.Client{
+		Timeout: 60 * time.Second,
+	}
+	dockerClient, err := client.NewClientWithOpts(client.FromEnv)
+	if err != nil {
+		log.Fatalf("failed to make docker client: %s", err)
+	}
+	if *flagFrom == "" {
+		flag.Usage()
+		os.Exit(1)
+	}
+	versions := calculateVersions(httpClient, *flagFrom, *flagTo)
+	log.Printf("Testing dendrite versions: %v\n", versions)
+
+	branchToImageID := buildDendriteImages(httpClient, dockerClient, *flagTempDir, *flagBuildConcurrency, versions)
+
+	// make a shared postgres volume
+	volume, err := dockerClient.VolumeCreate(context.Background(), volume.VolumeCreateBody{
+		Name: "dendrite_upgrade_test",
+	})
+	if err != nil {
+		log.Fatalf("failed to make docker volume: %s", err)
+	}
+
+	failed := false
+	defer func() {
+		perr := recover()
+		log.Println("removing postgres volume")
+		verr := dockerClient.VolumeRemove(context.Background(), volume.Name, true)
+		if perr == nil {
+			perr = verr
+		}
+		if perr != nil {
+			panic(perr)
+		}
+		if failed {
+			os.Exit(1)
+		}
+	}()
+
+	// run through images sequentially
+	for _, v := range versions {
+		if err = loadAndRunTests(dockerClient, volume.Name, v, branchToImageID); err != nil {
+			log.Printf("failed to run tests for %v: %s\n", v, err)
+			failed = true
+			break
+		}
+	}
+	if err := verifyTests(dockerClient, volume.Name, versions, branchToImageID); err != nil {
+		log.Printf("failed to verify test results: %s", err)
+		failed = true
+	}
+}
diff --git a/cmd/dendrite-upgrade-tests/tar.go b/cmd/dendrite-upgrade-tests/tar.go
new file mode 100644
index 00000000..9eadbb3d
--- /dev/null
+++ b/cmd/dendrite-upgrade-tests/tar.go
@@ -0,0 +1,57 @@
+package main
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// From https://gist.github.com/mimoo/25fc9716e0f1353791f5908f94d6e726
+// Modified to strip off top-level when compressing
+func compress(src string, buf io.Writer) error {
+	// tar > gzip > buf
+	zr := gzip.NewWriter(buf)
+	tw := tar.NewWriter(zr)
+
+	// walk through every file in the folder
+	_ = filepath.Walk(src, func(file string, fi os.FileInfo, e error) error {
+		// generate tar header
+		header, err := tar.FileInfoHeader(fi, file)
+		if err != nil {
+			return err
+		}
+
+		// must provide real name
+		// (see https://golang.org/src/archive/tar/common.go?#L626)
+		header.Name = strings.TrimPrefix(filepath.ToSlash(file), src+"/")
+		// write header
+		if err := tw.WriteHeader(header); err != nil {
+			return err
+		}
+		// if not a dir, write file content
+		if !fi.IsDir() {
+			data, err := os.Open(file)
+			if err != nil {
+				return err
+			}
+			if _, err := io.Copy(tw, data); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+
+	// produce tar
+	if err := tw.Close(); err != nil {
+		return err
+	}
+	// produce gzip
+	if err := zr.Close(); err != nil {
+		return err
+	}
+	//
+	return nil
+}
diff --git a/cmd/dendrite-upgrade-tests/tests.go b/cmd/dendrite-upgrade-tests/tests.go
new file mode 100644
index 00000000..e02af92a
--- /dev/null
+++ b/cmd/dendrite-upgrade-tests/tests.go
@@ -0,0 +1,192 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/matrix-org/gomatrix"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const userPassword = "this_is_a_long_password"
+
+type user struct {
+	userID    string
+	localpart string
+	client    *gomatrix.Client
+}
+
+// runTests performs the following operations:
+//  - register alice and bob with branch name muxed into the localpart
+//  - create a DM room for the 2 users and exchange messages
+//  - create/join a public #global room and exchange messages
+func runTests(baseURL, branchName string) error {
+	// register 2 users
+	users := []user{
+		{
+			localpart: "alice" + branchName,
+		},
+		{
+			localpart: "bob" + branchName,
+		},
+	}
+	for i, u := range users {
+		client, err := gomatrix.NewClient(baseURL, "", "")
+		if err != nil {
+			return err
+		}
+		resp, err := client.RegisterDummy(&gomatrix.ReqRegister{
+			Username: strings.ToLower(u.localpart),
+			Password: userPassword,
+		})
+		if err != nil {
+			return fmt.Errorf("failed to register %s: %s", u.localpart, err)
+		}
+		client, err = gomatrix.NewClient(baseURL, resp.UserID, resp.AccessToken)
+		if err != nil {
+			return err
+		}
+		users[i].client = client
+		users[i].userID = resp.UserID
+	}
+
+	// create DM room, join it and exchange messages
+	createRoomResp, err := users[0].client.CreateRoom(&gomatrix.ReqCreateRoom{
+		Preset:   "trusted_private_chat",
+		Invite:   []string{users[1].userID},
+		IsDirect: true,
+	})
+	if err != nil {
+		return fmt.Errorf("failed to create DM room: %s", err)
+	}
+	dmRoomID := createRoomResp.RoomID
+	if _, err = users[1].client.JoinRoom(dmRoomID, "", nil); err != nil {
+		return fmt.Errorf("failed to join DM room: %s", err)
+	}
+	msgs := []struct {
+		client *gomatrix.Client
+		text   string
+	}{
+		{
+			client: users[0].client, text: "1: " + branchName,
+		},
+		{
+			client: users[1].client, text: "2: " + branchName,
+		},
+		{
+			client: users[0].client, text: "3: " + branchName,
+		},
+		{
+			client: users[1].client, text: "4: " + branchName,
+		},
+	}
+	for _, msg := range msgs {
+		_, err = msg.client.SendText(dmRoomID, msg.text)
+		if err != nil {
+			return fmt.Errorf("failed to send text in dm room: %s", err)
+		}
+	}
+
+	// attempt to create/join the shared public room
+	publicRoomID := ""
+	createRoomResp, err = users[0].client.CreateRoom(&gomatrix.ReqCreateRoom{
+		RoomAliasName: "global",
+		Preset:        "public_chat",
+	})
+	if err != nil { // this is okay and expected if the room already exists and the aliases clash
+		// try to join it
+		_, domain, err2 := gomatrixserverlib.SplitID('@', users[0].userID)
+		if err2 != nil {
+			return fmt.Errorf("failed to split user ID: %s, %s", users[0].userID, err2)
+		}
+		joinRoomResp, err2 := users[0].client.JoinRoom(fmt.Sprintf("#global:%s", domain), "", nil)
+		if err2 != nil {
+			return fmt.Errorf("alice failed to join public room: %s", err2)
+		}
+		publicRoomID = joinRoomResp.RoomID
+	} else {
+		publicRoomID = createRoomResp.RoomID
+	}
+	if _, err = users[1].client.JoinRoom(publicRoomID, "", nil); err != nil {
+		return fmt.Errorf("bob failed to join public room: %s", err)
+	}
+	// send messages
+	for _, msg := range msgs {
+		_, err = msg.client.SendText(publicRoomID, "public "+msg.text)
+		if err != nil {
+			return fmt.Errorf("failed to send text in public room: %s", err)
+		}
+	}
+	log.Printf("OK! rooms(public=%s, dm=%s) users(%s, %s)\n", publicRoomID, dmRoomID, users[0].userID, users[1].userID)
+	return nil
+}
+
+// verifyTestsRan checks that the HS has the right rooms/messages
+func verifyTestsRan(baseURL string, branchNames []string) error {
+	log.Println("Verifying tests....")
+	// check we can login as all users
+	var resp *gomatrix.RespLogin
+	for _, branchName := range branchNames {
+		client, err := gomatrix.NewClient(baseURL, "", "")
+		if err != nil {
+			return err
+		}
+		userLocalparts := []string{
+			"alice" + branchName,
+			"bob" + branchName,
+		}
+		for _, userLocalpart := range userLocalparts {
+			resp, err = client.Login(&gomatrix.ReqLogin{
+				Type:     "m.login.password",
+				User:     strings.ToLower(userLocalpart),
+				Password: userPassword,
+			})
+			if err != nil {
+				return fmt.Errorf("failed to login as %s: %s", userLocalpart, err)
+			}
+			if resp.AccessToken == "" {
+				return fmt.Errorf("failed to login, bad response: %+v", resp)
+			}
+		}
+	}
+	log.Println("    accounts exist: OK")
+	client, err := gomatrix.NewClient(baseURL, resp.UserID, resp.AccessToken)
+	if err != nil {
+		return err
+	}
+	_, domain, err := gomatrixserverlib.SplitID('@', client.UserID)
+	if err != nil {
+		return err
+	}
+	u := client.BuildURL("directory", "room", fmt.Sprintf("#global:%s", domain))
+	r := struct {
+		RoomID string `json:"room_id"`
+	}{}
+	err = client.MakeRequest("GET", u, nil, &r)
+	if err != nil {
+		return fmt.Errorf("failed to /directory: %s", err)
+	}
+	if r.RoomID == "" {
+		return fmt.Errorf("/directory lookup returned no room ID")
+	}
+	log.Println("    public room exists: OK")
+
+	history, err := client.Messages(r.RoomID, client.Store.LoadNextBatch(client.UserID), "", 'b', 100)
+	if err != nil {
+		return fmt.Errorf("failed to get /messages: %s", err)
+	}
+	// we expect 4 messages per version
+	msgCount := 0
+	for _, ev := range history.Chunk {
+		if ev.Type == "m.room.message" {
+			msgCount += 1
+		}
+	}
+	wantMsgCount := len(branchNames) * 4
+	if msgCount != wantMsgCount {
+		return fmt.Errorf("got %d messages in global room, want %d", msgCount, wantMsgCount)
+	}
+	log.Println("    messages exist: OK")
+	return nil
+}