resilien
/
terraform
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Stricter pg backend locking during workspace creation

This commit is contained in:
Mars Hall 2019-03-05 11:19:56 -08:00
parent 31c9776d55
commit ccf549a62d
1 changed files with 26 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
backend/remote-state/pg/client.go
View File

@ -72,15 +72,27 @@ func (c *RemoteClient) Lock(info *state.LockInfo) (string, error) {
info.ID = lockID
}
// Try to acquire lock for the existing row.
query := `SELECT %s.id, pg_try_advisory_lock(%s.id) FROM %s.%s WHERE %s.name = $1`
// Local helper function so we can call it multiple places
//
lockUnlock := func(pgLockId string) error {
query := `SELECT pg_advisory_unlock(%s)`
row := c.Client.QueryRow(fmt.Sprintf(query, pgLockId))
var didUnlock []byte
err := row.Scan(&didUnlock)
if err != nil {
return &state.LockError{Info: c.info, Err: err}
}
return nil
}
// Try to acquire locks for the existing row `id` and the creation lock `-1`.
query := `SELECT %s.id, pg_try_advisory_lock(%s.id), pg_try_advisory_lock(-1) FROM %s.%s WHERE %s.name = $1`
row := c.Client.QueryRow(fmt.Sprintf(query, statesTableName, statesTableName, c.SchemaName, statesTableName, statesTableName), c.Name)
var pgLockId, didLock []byte
err = row.Scan(&pgLockId, &didLock)
var pgLockId, didLock, didLockForCreate []byte
err = row.Scan(&pgLockId, &didLock, &didLockForCreate)
switch {
case err == sql.ErrNoRows:
// When the row does not yet exist in state, take
// the `-1` lock to create the new row.
// No rows means we're creating the workspace. Take the creation lock.
innerRow := c.Client.QueryRow(`SELECT pg_try_advisory_lock(-1)`)
var innerDidLock []byte
err := innerRow.Scan(&innerDidLock)
@ -94,8 +106,16 @@ func (c *RemoteClient) Lock(info *state.LockInfo) (string, error) {
case err != nil:
return "", &state.LockError{Info: info, Err: err}
case string(didLock) == "false":
// Existing workspace is already locked. Release the attempted creation lock.
lockUnlock("-1")
return "", &state.LockError{Info: info, Err: fmt.Errorf("Workspace is already locked: %s", c.Name)}
case string(didLockForCreate) == "false":
// Someone has the creation lock already. Release the existing workspace because it might not be safe to touch.
lockUnlock(string(pgLockId))
return "", &state.LockError{Info: info, Err: fmt.Errorf("Cannot lock workspace; already locked for workspace creation: %s", c.Name)}
default:
// Existing workspace is now locked. Release the attempted creation lock.
lockUnlock("-1")
info.Path = string(pgLockId)
}
c.info = info
@ -116,9 +136,6 @@ func (c *RemoteClient) Unlock(id string) error {
if err != nil {
return &state.LockError{Info: c.info, Err: err}
}
if string(didUnlock) == "false" {
return &state.LockError{Info: c.info, Err: fmt.Errorf("Workspace is already unlocked: %s", c.Name)}
}
c.info = nil
}
return nil