Implement DiskId()

License: MIT
Signed-off-by: Kevin Atkinson <k@kevina.org>

repo/fsrepo/config_test.go

@@ -75,17 +75,28 @@ func TestDefaultDatastoreConfig(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir) // clean up
-	repo := FSRepo{path: dir}
 
 	config := new(config.Datastore)
 	err = json.Unmarshal(defaultConfig, config)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ds, err := repo.constructDatastore(config.Spec)
+
+	dsc, err := AnyDatastoreConfig(config.Spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := "/blocks:{flatfs;blocks;/repo/flatfs/shard/v1/next-to-last/2};/:{levelds;datastore};"
+	if dsc.DiskId() != expected {
+		t.Errorf("expected '%s' got '%s' as DiskId", expected, dsc.DiskId())
+	}
+
+	ds, err := dsc.Create(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	if typ := reflect.TypeOf(ds).String(); typ != "*syncmount.Datastore" {
 		t.Errorf("expected '*syncmount.Datastore' got '%s'", typ)
 	}
@@ -102,17 +113,28 @@ func TestLevelDbConfig(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir) // clean up
-	repo := FSRepo{path: dir}
 
 	spec := make(map[string]interface{})
 	err = json.Unmarshal(leveldbConfig, &spec)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ds, err := repo.constructDatastore(spec)
+
+	dsc, err := AnyDatastoreConfig(spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := "levelds;datastore"
+	if dsc.DiskId() != expected {
+		t.Errorf("expected '%s' got '%s' as DiskId", expected, dsc.DiskId())
+	}
+
+	ds, err := dsc.Create(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	if typ := reflect.TypeOf(ds).String(); typ != "*leveldb.datastore" {
 		t.Errorf("expected '*leveldb.datastore' got '%s'", typ)
 	}
@@ -129,17 +151,28 @@ func TestFlatfsConfig(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir) // clean up
-	repo := FSRepo{path: dir}
 
 	spec := make(map[string]interface{})
 	err = json.Unmarshal(flatfsConfig, &spec)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ds, err := repo.constructDatastore(spec)
+
+	dsc, err := AnyDatastoreConfig(spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := "flatfs;blocks;/repo/flatfs/shard/v1/next-to-last/2"
+	if dsc.DiskId() != expected {
+		t.Errorf("expected '%s' got '%s' as DiskId", expected, dsc.DiskId())
+	}
+
+	ds, err := dsc.Create(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	if typ := reflect.TypeOf(ds).String(); typ != "*flatfs.Datastore" {
 		t.Errorf("expected '*flatfs.Datastore' got '%s'", typ)
 	}
@@ -156,17 +189,28 @@ func TestMeasureConfig(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir) // clean up
-	repo := FSRepo{path: dir}
 
 	spec := make(map[string]interface{})
 	err = json.Unmarshal(measureConfig, &spec)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ds, err := repo.constructDatastore(spec)
+
+	dsc, err := AnyDatastoreConfig(spec)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := "flatfs;blocks;/repo/flatfs/shard/v1/next-to-last/2"
+	if dsc.DiskId() != expected {
+		t.Errorf("expected '%s' got '%s' as DiskId", expected, dsc.DiskId())
+	}
+
+	ds, err := dsc.Create(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	if typ := reflect.TypeOf(ds).String(); typ != "*measure.measure" {
 		t.Errorf("expected '*measure.measure' got '%s'", typ)
 	}

repo/fsrepo/datastores.go

@@ -1,6 +1,7 @@
 package fsrepo
 
 import (
+	"bytes"
 	"fmt"
 	"path/filepath"
 
@@ -18,9 +19,11 @@ import (
 type ConfigFromMap func(map[string]interface{}) (DatastoreConfig, error)
 
 type DatastoreConfig interface {
-	// DiskId is a unique id representing the Datastore config as stored on disk, runtime config values are not
-	// part of this Id.  No length limit.
-	//DiskId() string
+	// DiskId is a unique id representing the Datastore config as
+	// stored on disk, runtime config values are not part of this Id.
+	// Returns an empty string if the datastore does not have an on
+	// disk representation. No length limit.
+	DiskId() string
 
 	// Create instantiate a new datastore from this config
 	Create(path string) (repo.Datastore, error)
@@ -91,6 +94,14 @@ func MountDatastoreConfig(params map[string]interface{}) (DatastoreConfig, error
 	return &res, nil
 }
 
+func (c *mountDatastoreConfig) DiskId() string {
+	buf := new(bytes.Buffer)
+	for _, m := range c.mounts {
+		fmt.Fprintf(buf, "%s:{%s};", m.prefix.String(), m.ds.DiskId())
+	}
+	return buf.String()
+}
+
 func (c *mountDatastoreConfig) Create(path string) (repo.Datastore, error) {
 	mounts := make([]mount.Mount, len(c.mounts))
 	for i, m := range c.mounts {
@@ -136,6 +147,10 @@ func FlatfsDatastoreConfig(params map[string]interface{}) (DatastoreConfig, erro
 	return &c, nil
 }
 
+func (c *flatfsDatastoreConfig) DiskId() string {
+	return fmt.Sprintf("flatfs;%s;%s", c.path, c.shardFun.String())
+}
+
 func (c *flatfsDatastoreConfig) Create(path string) (repo.Datastore, error) {
 	p := c.path
 	if !filepath.IsAbs(p) {
@@ -173,6 +188,10 @@ func LeveldsDatastoreConfig(params map[string]interface{}) (DatastoreConfig, err
 	return &c, nil
 }
 
+func (c *leveldsDatastoreConfig) DiskId() string {
+	return fmt.Sprintf("levelds;%s", c.path)
+}
+
 func (c *leveldsDatastoreConfig) Create(path string) (repo.Datastore, error) {
 	p := c.path
 	if !filepath.IsAbs(p) {
@@ -192,6 +211,10 @@ func MemDatastoreConfig(params map[string]interface{}) (DatastoreConfig, error)
 	return &memDatastoreConfig{params}, nil
 }
 
+func (c *memDatastoreConfig) DiskId() string {
+	return ""
+}
+
 func (c *memDatastoreConfig) Create(string) (repo.Datastore, error) {
 	return ds.NewMapDatastore(), nil
 }
@@ -226,6 +249,10 @@ func (c *logDatastoreConfig) Create(path string) (repo.Datastore, error) {
 	return ds.NewLogDatastore(child, c.name), nil
 }
 
+func (c *logDatastoreConfig) DiskId() string {
+	return c.child.DiskId()
+}
+
 type measureDatastoreConfig struct {
 	child  DatastoreConfig
 	prefix string
@@ -247,6 +274,10 @@ func MeasureDatastoreConfig(params map[string]interface{}) (DatastoreConfig, err
 	return &measureDatastoreConfig{child, prefix}, nil
 }
 
+func (c *measureDatastoreConfig) DiskId() string {
+	return c.child.DiskId()
+}
+
 func (c measureDatastoreConfig) Create(path string) (repo.Datastore, error) {
 	child, err := c.child.Create(path)
 	if err != nil {

repo/fsrepo/fsrepo.go

@@ -1,6 +1,7 @@
 package fsrepo
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -357,31 +358,71 @@ func (r *FSRepo) openKeystore() error {
 
 // openDatastore returns an error if the config file is not present.
 func (r *FSRepo) openDatastore() error {
-	if r.config.Datastore.Spec != nil {
-		d, err := r.constructDatastore(r.config.Datastore.Spec)
+	if r.config.Datastore.Type != "" || r.config.Datastore.Path != "" {
+		return fmt.Errorf("old style datatstore config detected")
+	} else if r.config.Datastore.Spec == nil {
+		return fmt.Errorf("required Datastore.Spec entry missing form config file")
+	}
+
+	dsc, err := AnyDatastoreConfig(r.config.Datastore.Spec)
+	if err != nil {
+		return err
+	}
+	diskId := dsc.DiskId()
+
+	oldDiskId, err := r.readDiskId()
+	if err == nil {
+		if oldDiskId != diskId {
+			return fmt.Errorf("Datastore configuration of '%s' does not match what is on disk '%s'",
+				oldDiskId, diskId)
+		}
+	} else if os.IsNotExist(err) {
+		err := r.writeDiskId(diskId)
 		if err != nil {
 			return err
 		}
-		r.ds = d
-	} else if r.config.Datastore.Type != "" || r.config.Datastore.Path != "" {
-		return fmt.Errorf("old style datatstore config detected")
 	} else {
-		return fmt.Errorf("required Datastore.Spec entry missing form config file")
+		return err
 	}
 
+	d, err := dsc.Create(r.path)
+	if err != nil {
+		return err
+	}
+	r.ds = d
+
 	// Wrap it with metrics gathering
 	prefix := "ipfs.fsrepo.datastore"
 	r.ds = measure.New(prefix, r.ds)
 
 	return nil
 }
 
-func (r *FSRepo) constructDatastore(params map[string]interface{}) (repo.Datastore, error) {
-	cfg, err := AnyDatastoreConfig(params)
+var DiskIdFn = "dsid"
+
+func (r *FSRepo) readDiskId() (string, error) {
+	fn, err := config.Path(r.path, DiskIdFn)
 	if err != nil {
-		return nil, err
+		return "", err
+	}
+	b, err := ioutil.ReadFile(fn)
+	if err != nil {
+		return "", err
+	}
+	b = bytes.TrimSpace(b)
+	return string(b), nil
+}
+
+func (r *FSRepo) writeDiskId(newId string) error {
+	fn, err := config.Path(r.path, DiskIdFn)
+	if err != nil {
+		return err
 	}
-	return cfg.Create(r.path)
+	err = ioutil.WriteFile(fn, []byte(newId), 0666)
+	if err != nil {
+		return err
+	}
+	return nil
 }
 
 // Close closes the FSRepo, releasing held resources.