1 files changed, 107 insertions, 0 deletions
diff --git a/src/mongo/gotools/mongodump/metadata_dump.go b/src/mongo/gotools/mongodump/metadata_dump.go
new file mode 100644
index 00000000000..5a4382b6d2e
--- /dev/null
+++ b/src/mongo/gotools/mongodump/metadata_dump.go
@@ -0,0 +1,107 @@
+package mongodump
+
+import (
+	"bufio"
+	"fmt"
+	"github.com/mongodb/mongo-tools/common/bsonutil"
+	"github.com/mongodb/mongo-tools/common/db"
+	"github.com/mongodb/mongo-tools/common/intents"
+	"github.com/mongodb/mongo-tools/common/json"
+	"github.com/mongodb/mongo-tools/common/log"
+	"gopkg.in/mgo.v2/bson"
+)
+
+// Metadata holds information about a collection's options and indexes.
+type Metadata struct {
+	Options interface{}   `json:"options,omitempty"`
+	Indexes []interface{} `json:"indexes"`
+}
+
+// IndexDocumentFromDB is used internally to preserve key ordering.
+type IndexDocumentFromDB struct {
+	Options bson.M `bson:",inline"`
+	Key     bson.D `bson:"key"`
+}
+
+// dumpMetadata gets the metadata for a collection and writes it
+// in readable JSON format.
+func (dump *MongoDump) dumpMetadata(intent *intents.Intent) error {
+	var err error
+
+	nsID := fmt.Sprintf("%v.%v", intent.DB, intent.C)
+	meta := Metadata{
+		// We have to initialize Indexes to an empty slice, not nil, so that an empty
+		// array is marshalled into json instead of null. That is, {indexes:[]} is okay
+		// but {indexes:null} will cause assertions in our legacy C++ mongotools
+		Indexes: []interface{}{},
+	}
+
+	// The collection options were already gathered while building the list of intents.
+	// We convert them to JSON so that they can be written to the metadata json file as text.
+	if intent.Options != nil {
+		if meta.Options, err = bsonutil.ConvertBSONValueToJSON(*intent.Options); err != nil {
+			return fmt.Errorf("error converting collection options to JSON: %v", err)
+		}
+	} else {
+		meta.Options = nil
+	}
+
+	// Second, we read the collection's index information by either calling
+	// listIndexes (pre-2.7 systems) or querying system.indexes.
+	// We keep a running list of all the indexes
+	// for the current collection as we iterate over the cursor, and include
+	// that list as the "indexes" field of the metadata document.
+	log.Logvf(log.DebugHigh, "\treading indexes for `%v`", nsID)
+
+	session, err := dump.sessionProvider.GetSession()
+	if err != nil {
+		return err
+	}
+	defer session.Close()
+
+	// get the indexes
+	indexesIter, err := db.GetIndexes(session.DB(intent.DB).C(intent.C))
+	if err != nil {
+		return err
+	}
+	if indexesIter == nil {
+		log.Logvf(log.Always, "the collection %v appears to have been dropped after the dump started", intent.Namespace())
+		return nil
+	}
+
+	indexOpts := &bson.D{}
+	for indexesIter.Next(indexOpts) {
+		convertedIndex, err := bsonutil.ConvertBSONValueToJSON(*indexOpts)
+		if err != nil {
+			return fmt.Errorf("error converting index (%#v): %v", convertedIndex, err)
+		}
+		meta.Indexes = append(meta.Indexes, convertedIndex)
+	}
+
+	if err := indexesIter.Err(); err != nil {
+		return fmt.Errorf("error getting indexes for collection `%v`: %v", nsID, err)
+	}
+
+	// Finally, we send the results to the writer as JSON bytes
+	jsonBytes, err := json.Marshal(meta)
+	if err != nil {
+		return fmt.Errorf("error marshalling metadata json for collection `%v`: %v", nsID, err)
+	}
+
+	err = intent.MetadataFile.Open()
+	if err != nil {
+		return err
+	}
+	defer intent.MetadataFile.Close()
+	// make a buffered writer for nicer disk i/o
+	w := bufio.NewWriter(intent.MetadataFile)
+	_, err = w.Write(jsonBytes)
+	if err != nil {
+		return fmt.Errorf("error writing metadata for collection `%v` to disk: %v", nsID, err)
+	}
+	err = w.Flush()
+	if err != nil {
+		return fmt.Errorf("error writing metadata for collection `%v` to disk: %v", nsID, err)
+	}
+	return nil
+}