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cassandra.go
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cassandra.go
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package cassandra
import (
"errors"
"fmt"
"io"
"io/ioutil"
nurl "net/url"
"strconv"
"strings"
"time"
"github.com/gocql/gocql"
"github.com/golang-migrate/migrate/database"
)
func init() {
db := new(Cassandra)
database.Register("cassandra", db)
}
var DefaultMigrationsTable = "schema_migrations"
var (
ErrNilConfig = errors.New("no config")
ErrNoKeyspace = errors.New("no keyspace provided")
ErrDatabaseDirty = errors.New("database is dirty")
ErrClosedSession = errors.New("session is closed")
)
type Config struct {
MigrationsTable string
KeyspaceName string
}
type Cassandra struct {
session *gocql.Session
isLocked bool
// Open and WithInstance need to guarantee that config is never nil
config *Config
}
func WithInstance(session *gocql.Session, config *Config) (database.Driver, error) {
if config == nil {
return nil, ErrNilConfig
} else if len(config.KeyspaceName) == 0 {
return nil, ErrNoKeyspace
}
if session.Closed() {
return nil, ErrClosedSession
}
if len(config.MigrationsTable) == 0 {
config.MigrationsTable = DefaultMigrationsTable
}
c := &Cassandra{
session: session,
config: config,
}
if err := c.ensureVersionTable(); err != nil {
return nil, err
}
return c, nil
}
func (c *Cassandra) Open(url string) (database.Driver, error) {
u, err := nurl.Parse(url)
if err != nil {
return nil, err
}
// Check for missing mandatory attributes
if len(u.Path) == 0 {
return nil, ErrNoKeyspace
}
cluster := gocql.NewCluster(u.Host)
cluster.Keyspace = strings.TrimPrefix(u.Path, "/")
cluster.Consistency = gocql.All
cluster.Timeout = 1 * time.Minute
if len(u.Query().Get("username")) > 0 && len(u.Query().Get("password")) > 0 {
authenticator := gocql.PasswordAuthenticator{
Username: u.Query().Get("username"),
Password: u.Query().Get("password"),
}
cluster.Authenticator = authenticator
}
// Retrieve query string configuration
if len(u.Query().Get("consistency")) > 0 {
var consistency gocql.Consistency
consistency, err = parseConsistency(u.Query().Get("consistency"))
if err != nil {
return nil, err
}
cluster.Consistency = consistency
}
if len(u.Query().Get("protocol")) > 0 {
var protoversion int
protoversion, err = strconv.Atoi(u.Query().Get("protocol"))
if err != nil {
return nil, err
}
cluster.ProtoVersion = protoversion
}
if len(u.Query().Get("timeout")) > 0 {
var timeout time.Duration
timeout, err = time.ParseDuration(u.Query().Get("timeout"))
if err != nil {
return nil, err
}
cluster.Timeout = timeout
}
session, err := cluster.CreateSession()
if err != nil {
return nil, err
}
return WithInstance(session, &Config{
KeyspaceName: strings.TrimPrefix(u.Path, "/"),
MigrationsTable: u.Query().Get("x-migrations-table"),
})
}
func (c *Cassandra) Close() error {
c.session.Close()
return nil
}
func (c *Cassandra) Lock() error {
if c.isLocked {
return database.ErrLocked
}
c.isLocked = true
return nil
}
func (c *Cassandra) Unlock() error {
c.isLocked = false
return nil
}
func (c *Cassandra) Run(migration io.Reader) error {
migr, err := ioutil.ReadAll(migration)
if err != nil {
return err
}
// run migration
query := string(migr[:])
if err := c.session.Query(query).Exec(); err != nil {
// TODO: cast to Cassandra error and get line number
return database.Error{OrigErr: err, Err: "migration failed", Query: migr}
}
return nil
}
func (c *Cassandra) SetVersion(version int, dirty bool) error {
query := `TRUNCATE "` + c.config.MigrationsTable + `"`
if err := c.session.Query(query).Exec(); err != nil {
return &database.Error{OrigErr: err, Query: []byte(query)}
}
if version >= 0 {
query = `INSERT INTO "` + c.config.MigrationsTable + `" (version, dirty) VALUES (?, ?)`
if err := c.session.Query(query, version, dirty).Exec(); err != nil {
return &database.Error{OrigErr: err, Query: []byte(query)}
}
}
return nil
}
// Return current keyspace version
func (c *Cassandra) Version() (version int, dirty bool, err error) {
query := `SELECT version, dirty FROM "` + c.config.MigrationsTable + `" LIMIT 1`
err = c.session.Query(query).Scan(&version, &dirty)
switch {
case err == gocql.ErrNotFound:
return database.NilVersion, false, nil
case err != nil:
if _, ok := err.(*gocql.Error); ok {
return database.NilVersion, false, nil
}
return 0, false, &database.Error{OrigErr: err, Query: []byte(query)}
default:
return version, dirty, nil
}
}
func (c *Cassandra) Drop() error {
// select all tables in current schema
query := fmt.Sprintf(`SELECT table_name from system_schema.tables WHERE keyspace_name='%s'`, c.config.KeyspaceName)
iter := c.session.Query(query).Iter()
var tableName string
for iter.Scan(&tableName) {
err := c.session.Query(fmt.Sprintf(`DROP TABLE %s`, tableName)).Exec()
if err != nil {
return err
}
}
// Re-create the version table
return c.ensureVersionTable()
}
// Ensure version table exists
func (c *Cassandra) ensureVersionTable() error {
err := c.session.Query(fmt.Sprintf("CREATE TABLE IF NOT EXISTS %s (version bigint, dirty boolean, PRIMARY KEY(version))", c.config.MigrationsTable)).Exec()
if err != nil {
return err
}
if _, _, err = c.Version(); err != nil {
return err
}
return nil
}
// ParseConsistency wraps gocql.ParseConsistency
// to return an error instead of a panicking.
func parseConsistency(consistencyStr string) (consistency gocql.Consistency, err error) {
defer func() {
if r := recover(); r != nil {
var ok bool
err, ok = r.(error)
if !ok {
err = fmt.Errorf("Failed to parse consistency \"%s\": %v", consistencyStr, r)
}
}
}()
consistency = gocql.ParseConsistency(consistencyStr)
return consistency, nil
}