directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/filer/cassandra_store/cassandra_store.go

@@ -0,0 +1,87 @@
+package cassandra_store
+
+import (
+	"fmt"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+
+	"github.com/gocql/gocql"
+)
+
+/*
+
+Basically you need a table just like this:
+
+CREATE TABLE seaweed_files (
+   path varchar,
+   fids list<varchar>,
+   PRIMARY KEY (path)
+);
+
+Need to match flat_namespace.FlatNamespaceStore interface
+	Put(fullFileName string, fid string) (err error)
+	Get(fullFileName string) (fid string, err error)
+	Delete(fullFileName string) (fid string, err error)
+
+*/
+type CassandraStore struct {
+	cluster *gocql.ClusterConfig
+	session *gocql.Session
+}
+
+func NewCassandraStore(keyspace string, hosts ...string) (c *CassandraStore, err error) {
+	c = &CassandraStore{}
+	c.cluster = gocql.NewCluster(hosts...)
+	c.cluster.Keyspace = keyspace
+	c.cluster.Consistency = gocql.Quorum
+	c.session, err = c.cluster.CreateSession()
+	if err != nil {
+		glog.V(0).Infof("Failed to open cassandra store, hosts %v, keyspace %s", hosts, keyspace)
+	}
+	return
+}
+
+func (c *CassandraStore) Put(fullFileName string, fid string) (err error) {
+	var input []string
+	input = append(input, fid)
+	if err := c.session.Query(
+		`INSERT INTO seaweed_files (path, fids) VALUES (?, ?)`,
+		fullFileName, input).Exec(); err != nil {
+		glog.V(0).Infof("Failed to save file %s with id %s: %v", fullFileName, fid, err)
+		return err
+	}
+	return nil
+}
+func (c *CassandraStore) Get(fullFileName string) (fid string, err error) {
+	var output []string
+	if err := c.session.Query(
+		`select fids FROM seaweed_files WHERE path = ? LIMIT 1`,
+		fullFileName).Consistency(gocql.One).Scan(&output); err != nil {
+		if err != gocql.ErrNotFound {
+			glog.V(0).Infof("Failed to find file %s: %v", fullFileName, fid, err)
+		}
+	}
+	if len(output) == 0 {
+		return "", fmt.Errorf("No file id found for %s", fullFileName)
+	}
+	return output[0], nil
+}
+
+// Currently the fid is not returned
+func (c *CassandraStore) Delete(fullFileName string) (fid string, err error) {
+	if err := c.session.Query(
+		`DELETE FROM seaweed_files WHERE path = ?`,
+		fullFileName).Exec(); err != nil {
+		if err != gocql.ErrNotFound {
+			glog.V(0).Infof("Failed to delete file %s: %v", fullFileName, err)
+		}
+		return "", err
+	}
+	return "", nil
+}
+
+func (c *CassandraStore) Close() {
+	if c.session != nil {
+		c.session.Close()
+	}
+}

weed/filer/cassandra_store/schema.cql

@@ -0,0 +1,22 @@
+/*
+
+Here is the CQL to create the table.CassandraStore
+
+Optionally you can adjust the keyspace name and replication settings.
+
+For production server, very likely you want to set replication_factor to 3
+
+*/
+
+create keyspace seaweed WITH replication = {
+  'class':'SimpleStrategy',
+  'replication_factor':1
+};
+
+use seaweed;
+
+CREATE TABLE seaweed_files (
+   path varchar,
+   fids list<varchar>,
+   PRIMARY KEY (path)
+);