Add filesystem metadata file on startup

Write a metadata file on startup with a unique id. Also add
a field to the ServerInfoResponse message that returns this unique id
as well as the path to the file on the server

10 files changed, 228 insertions, 9 deletions

diff --git a/NOTICE b/NOTICE
index 09c971854..49b4bc246 100644
--- a/NOTICE
+++ b/NOTICE
@@ -439,6 +439,35 @@ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LICENSE - gitlab.com/gitlab-org/gitaly/vendor/github.com/google/uuid
+Copyright (c) 2009,2014 Google Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 LICENSE - gitlab.com/gitlab-org/gitaly/vendor/github.com/grpc-ecosystem/go-grpc-middleware
                  Apache License
                            Version 2.0, January 2004
diff --git a/changelogs/unreleased/jc-filesystem-uuid.yml b/changelogs/unreleased/jc-filesystem-uuid.yml
new file mode 100644
index 000000000..5fd0244bb
--- /dev/null
+++ b/changelogs/unreleased/jc-filesystem-uuid.yml
@@ -0,0 +1,5 @@
+---
+title: Add filesystem metadata file on startup
+merge_request: 1289
+author:
+type: other
diff --git a/cmd/gitaly/main.go b/cmd/gitaly/main.go
index fb87ecfe3..f3f97413b 100644
--- a/cmd/gitaly/main.go
+++ b/cmd/gitaly/main.go
@@ -13,6 +13,7 @@ import (
 	"gitlab.com/gitlab-org/gitaly/internal/config"
 	"gitlab.com/gitlab-org/gitaly/internal/git"
 	"gitlab.com/gitlab-org/gitaly/internal/server"
+	"gitlab.com/gitlab-org/gitaly/internal/storage"
 	"gitlab.com/gitlab-org/gitaly/internal/tempdir"
 	"gitlab.com/gitlab-org/gitaly/internal/version"
 	"gitlab.com/gitlab-org/labkit/tracing"
@@ -152,6 +153,12 @@ func run(b *bootstrap.Bootstrap) error {
 		})
 	}
 
+	for _, shard := range config.Config.Storages {
+		if err = storage.WriteMetadataFile(shard); err != nil {
+			log.WithError(err).Error("Unable to write gitaly metadata file")
+		}
+	}
+
 	if err := b.Start(); err != nil {
 		return fmt.Errorf("unable to start the bootstrap: %v", err)
 	}
diff --git a/go.mod b/go.mod
index 0daf1038a..2f8d016c1 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@ require (
 	github.com/cloudflare/tableflip v0.0.0-20190329062924-8392f1641731
 	github.com/getsentry/raven-go v0.1.2
 	github.com/golang/protobuf v1.3.1
+	github.com/google/uuid v1.1.1
 	github.com/grpc-ecosystem/go-grpc-middleware v1.0.0
 	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0
 	github.com/kelseyhightower/envconfig v1.3.0
@@ -13,7 +14,7 @@ require (
 	github.com/sirupsen/logrus v1.2.0
 	github.com/stretchr/testify v1.2.2
 	github.com/tinylib/msgp v1.1.0 // indirect
-	gitlab.com/gitlab-org/gitaly-proto v1.32.0
+	gitlab.com/gitlab-org/gitaly-proto v1.33.0
 	gitlab.com/gitlab-org/labkit v0.0.0-20190221122536-0c3fc7cdd57c
 	golang.org/x/net v0.0.0-20190311183353-d8887717615a
 	golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4
diff --git a/go.sum b/go.sum
index cc56b0adb..70d35d346 100644
--- a/go.sum
+++ b/go.sum
@@ -38,6 +38,8 @@ github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfb
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
+github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/grpc-ecosystem/go-grpc-middleware v1.0.0 h1:Iju5GlWwrvL6UBg4zJJt3btmonfrMlCDdsejg4CZE7c=
 github.com/grpc-ecosystem/go-grpc-middleware v1.0.0/go.mod h1:FiyG127CGDf3tlThmgyCl78X/SZQqEOJBCDaAfeWzPs=
 github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0 h1:Ovs26xHkKqVztRpIrF/92BcuyuQ/YW4NSIpoGtfXNho=
@@ -102,8 +104,8 @@ github.com/uber/jaeger-client-go v2.15.0+incompatible h1:NP3qsSqNxh8VYr956ur1N/1
 github.com/uber/jaeger-client-go v2.15.0+incompatible/go.mod h1:WVhlPFC8FDjOFMMWRy2pZqQJSXxYSwNYOkTr/Z6d3Kk=
 github.com/uber/jaeger-lib v1.5.0 h1:OHbgr8l656Ub3Fw5k9SWnBfIEwvoHQ+W2y+Aa9D1Uyo=
 github.com/uber/jaeger-lib v1.5.0/go.mod h1:ComeNDZlWwrWnDv8aPp0Ba6+uUTzImX/AauajbLI56U=
-gitlab.com/gitlab-org/gitaly-proto v1.32.0 h1:TRe/iw/Gid1RNM2VzK+WICIw4/N7V5s0IdhmgiPyqNE=
-gitlab.com/gitlab-org/gitaly-proto v1.32.0/go.mod h1:zNjk/86bjwLVJ4NcvInBcXcLdptdRFQ28sYrdFbrFgY=
+gitlab.com/gitlab-org/gitaly-proto v1.33.0 h1:gSwV1hGpwrEauYcl81j214DRfUHAznBeeOMdwbvadnc=
+gitlab.com/gitlab-org/gitaly-proto v1.33.0/go.mod h1:zNjk/86bjwLVJ4NcvInBcXcLdptdRFQ28sYrdFbrFgY=
 gitlab.com/gitlab-org/labkit v0.0.0-20190221122536-0c3fc7cdd57c h1:xo48LcGsTCasKcJpQDBCCuZU+aP8uGaboUVvD7Lgm6g=
 gitlab.com/gitlab-org/labkit v0.0.0-20190221122536-0c3fc7cdd57c/go.mod h1:rYhLgfrbEcyfinG+R3EvKu6bZSsmwQqcXzLfHWSfUKM=
 go.uber.org/atomic v1.3.2 h1:2Oa65PReHzfn29GpvgsYwloV9AVFHPDk8tYxt2c2tr4=
diff --git a/internal/service/server/info.go b/internal/service/server/info.go
index 166eef943..ca54cf5d0 100644
--- a/internal/service/server/info.go
+++ b/internal/service/server/info.go
@@ -6,35 +6,47 @@ import (
 	"os"
 	"path"
 
+	grpc_logrus "github.com/grpc-ecosystem/go-grpc-middleware/logging/logrus"
 	"gitlab.com/gitlab-org/gitaly-proto/go/gitalypb"
+
 	"gitlab.com/gitlab-org/gitaly/internal/config"
 	"gitlab.com/gitlab-org/gitaly/internal/git"
+	"gitlab.com/gitlab-org/gitaly/internal/helper"
 	"gitlab.com/gitlab-org/gitaly/internal/helper/fstype"
+	"gitlab.com/gitlab-org/gitaly/internal/storage"
 	"gitlab.com/gitlab-org/gitaly/internal/version"
 )
 
 func (s *server) ServerInfo(ctx context.Context, in *gitalypb.ServerInfoRequest) (*gitalypb.ServerInfoResponse, error) {
 	gitVersion, err := git.Version()
+	if err != nil {
+		return nil, helper.ErrInternal(err)
+	}
 
 	var storageStatuses []*gitalypb.ServerInfoResponse_StorageStatus
 	for _, shard := range config.Config.Storages {
 		readable, writeable := shardCheck(shard.Path)
 		fsType := fstype.FileSystem(shard.Path)
 
+		gitalyMetadata, err := storage.ReadMetadataFile(shard)
+		if err != nil {
+			grpc_logrus.Extract(ctx).WithField("storage", shard).WithError(err).Error("reading gitaly metadata file")
+		}
+
 		storageStatuses = append(storageStatuses, &gitalypb.ServerInfoResponse_StorageStatus{
-			StorageName: shard.Name,
-			Readable:    readable,
-			Writeable:   writeable,
-			FsType:      fsType,
+			StorageName:  shard.Name,
+			Readable:     readable,
+			Writeable:    writeable,
+			FsType:       fsType,
+			FilesystemId: gitalyMetadata.GitalyFilesystemID,
 		})
-
 	}
 
 	return &gitalypb.ServerInfoResponse{
 		ServerVersion:   version.GetVersion(),
 		GitVersion:      gitVersion,
 		StorageStatuses: storageStatuses,
-	}, err
+	}, nil
 }
 
 func shardCheck(shardPath string) (readable bool, writeable bool) {
diff --git a/internal/service/server/info_test.go b/internal/service/server/info_test.go
index e6aa36f24..7559d068b 100644
--- a/internal/service/server/info_test.go
+++ b/internal/service/server/info_test.go
@@ -1,6 +1,7 @@
 package server
 
 import (
+	"io/ioutil"
 	"net"
 	"testing"
 
@@ -10,6 +11,7 @@ import (
 	"gitlab.com/gitlab-org/gitaly/internal/config"
 	"gitlab.com/gitlab-org/gitaly/internal/git"
 	"gitlab.com/gitlab-org/gitaly/internal/server/auth"
+	"gitlab.com/gitlab-org/gitaly/internal/storage"
 	"gitlab.com/gitlab-org/gitaly/internal/testhelper"
 	"gitlab.com/gitlab-org/gitaly/internal/version"
 	"google.golang.org/grpc"
@@ -36,6 +38,15 @@ func TestGitalyServerInfo(t *testing.T) {
 	}(config.Config.Storages)
 	config.Config.Storages = testStorages
 
+	tempDir, err := ioutil.TempDir("", "gitaly-bin")
+	require.NoError(t, err)
+
+	config.Config.BinDir = tempDir
+
+	require.NoError(t, storage.WriteMetadataFile(testStorages[0]))
+	metadata, err := storage.ReadMetadataFile(testStorages[0])
+	require.NoError(t, err)
+
 	c, err := client.ServerInfo(ctx, &gitalypb.ServerInfoRequest{})
 	require.NoError(t, err)
 
@@ -52,6 +63,7 @@ func TestGitalyServerInfo(t *testing.T) {
 
 	require.False(t, c.GetStorageStatuses()[1].Readable)
 	require.False(t, c.GetStorageStatuses()[1].Writeable)
+	require.Equal(t, metadata.GitalyFilesystemID, c.GetStorageStatuses()[0].FilesystemId)
 }
 
 func runServer(t *testing.T) (*grpc.Server, string) {
diff --git a/internal/storage/metadata.go b/internal/storage/metadata.go
new file mode 100644
index 000000000..90abf74f3
--- /dev/null
+++ b/internal/storage/metadata.go
@@ -0,0 +1,67 @@
+package storage
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+
+	"github.com/google/uuid"
+	"gitlab.com/gitlab-org/gitaly/internal/config"
+	"gitlab.com/gitlab-org/gitaly/internal/safe"
+)
+
+const (
+	// metadataFilename is the filename for a file we write on the gitaly server containing metadata about
+	// the filesystem
+	metadataFilename = ".gitaly-metadata"
+)
+
+// Metadata contains metadata about the filesystem
+type Metadata struct {
+	GitalyFilesystemID string `json:"gitaly_filesystem_id"`
+}
+
+// WriteMetadataFile marshals and writes a metadata file
+func WriteMetadataFile(storage config.Storage) error {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	path := filepath.Join(storage.Path, metadataFilename)
+
+	if _, err := os.Stat(path); !os.IsNotExist(err) {
+		return err
+	}
+
+	fw, err := safe.CreateFileWriter(ctx, path)
+	if err != nil {
+		return err
+	}
+
+	if err = json.NewEncoder(fw).Encode(&Metadata{
+		GitalyFilesystemID: uuid.New().String(),
+	}); err != nil {
+		return err
+	}
+
+	return fw.Commit()
+}
+
+// ReadMetadataFile reads and decodes the json metadata file
+func ReadMetadataFile(storage config.Storage) (Metadata, error) {
+	path := filepath.Join(storage.Path, metadataFilename)
+
+	var metadata Metadata
+
+	metadataFile, err := os.Open(path)
+	if err != nil {
+		return metadata, err
+	}
+	defer metadataFile.Close()
+
+	if err = json.NewDecoder(metadataFile).Decode(&metadata); err != nil {
+		return metadata, err
+	}
+
+	return metadata, nil
+}
diff --git a/internal/storage/metadata_test.go b/internal/storage/metadata_test.go
new file mode 100644
index 000000000..88bc5f6b3
--- /dev/null
+++ b/internal/storage/metadata_test.go
@@ -0,0 +1,83 @@
+package storage
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+	"gitlab.com/gitlab-org/gitaly/internal/config"
+)
+
+func readFilesystemID(t *testing.T, path string) string {
+	metadata := make(map[string]string)
+
+	f, err := os.Open(filepath.Join(path, metadataFilename))
+	require.NoError(t, err)
+	defer f.Close()
+
+	require.NoError(t, json.NewDecoder(f).Decode(&metadata))
+	return metadata["gitaly_filesystem_id"]
+}
+
+func TestWriteMetdataFile(t *testing.T) {
+	tempDir, err := ioutil.TempDir("", t.Name())
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, os.RemoveAll(tempDir))
+	}()
+
+	shard := config.Storage{
+		Path: tempDir,
+	}
+
+	require.NoError(t, WriteMetadataFile(shard))
+	require.NotEmpty(t, readFilesystemID(t, tempDir))
+}
+
+func TestWriteMetadataFile_AlreadyExists(t *testing.T) {
+	tempDir, err := ioutil.TempDir("", t.Name())
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, os.RemoveAll(tempDir))
+	}()
+
+	metadataPath := filepath.Join(tempDir, ".gitaly-metadata")
+	metadataFile, err := os.Create(metadataPath)
+	require.NoError(t, err)
+
+	m := Metadata{
+		GitalyFilesystemID: uuid.New().String(),
+	}
+
+	require.NoError(t, json.NewEncoder(metadataFile).Encode(&m))
+	require.NoError(t, metadataFile.Close())
+
+	require.NoError(t, WriteMetadataFile(config.Storage{
+		Path: tempDir,
+	}))
+
+	require.Equal(t, m.GitalyFilesystemID, readFilesystemID(t, tempDir), "WriteMetadataFile should not clobber the existing file")
+}
+
+func TestReadMetadataFile(t *testing.T) {
+	shard := config.Storage{
+		Path: "testdata",
+	}
+
+	metadata, err := ReadMetadataFile(shard)
+	require.NoError(t, err)
+	require.Equal(t, "test filesystem id", metadata.GitalyFilesystemID, "filesystem id should match the harded value in testdata/.gitaly-metadata")
+}
+
+func TestReadMetadataFile_FileNotExists(t *testing.T) {
+	shard := config.Storage{
+		Path: "/path/doesnt/exist",
+	}
+
+	_, err := ReadMetadataFile(shard)
+	require.Error(t, err)
+}
diff --git a/internal/storage/testdata/.gitaly-metadata b/internal/storage/testdata/.gitaly-metadata
new file mode 100644
index 000000000..f11b36eb8
--- /dev/null
+++ b/internal/storage/testdata/.gitaly-metadata
@@ -0,0 +1 @@
+{"gitaly_filesystem_id":"test filesystem id"}
\ No newline at end of file