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Add a mutex to BoltDB state to prevent lock issues

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Per https://www.sqlite.org/src/artifact/c230a7a24?ln=994-1081,
POSIX file advisory locks are unsafe to use within a single
process if multiple file descriptors are open for the same file.
Unfortunately, this has a strong potential to happen for
multithreaded usage of libpod, and could result in DB corruption.

To prevent this, wrap all access to BoltDB within a single
libpod instance in a mutex to ensure concurrent access cannot
occur.

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>
This commit is contained in:
Matthew Heon
2018-07-25 10:43:28 -04:00
parent c90b7400a8
commit 42bd9d3880
2 changed files with 50 additions and 23 deletions
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21
libpod/boltdb_state_internal.go
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@ -145,7 +145,15 @@ func validateDBAgainstConfig(bucket *bolt.Bucket, fieldName, runtimeValue string
return nil
}
// Open a connection to the database.
// Must be paired with a `defer closeDBCon()` on the returned database, to
// ensure the state is properly unlocked
func (s *BoltState) getDBCon() (*bolt.DB, error) {
// We need an in-memory lock to avoid issues around POSIX file advisory
// locks as described in the link below:
// https://www.sqlite.org/src/artifact/c230a7a24?ln=994-1081
s.dbLock.Lock()
db, err := bolt.Open(s.dbPath, 0600, nil)
if err != nil {
return nil, errors.Wrapf(err, "error opening database %s", s.dbPath)
@ -154,6 +162,17 @@ func (s *BoltState) getDBCon() (*bolt.DB, error) {
return db, nil
}
// Close a connection to the database.
// MUST be used in place of `db.Close()` to ensure proper unlocking of the
// state.
func (s *BoltState) closeDBCon(db *bolt.DB) error {
err := db.Close()
s.dbLock.Unlock()
return err
}
func getIDBucket(tx *bolt.Tx) (*bolt.Bucket, error) {
bkt := tx.Bucket(idRegistryBkt)
if bkt == nil {
@ -296,7 +315,7 @@ func (s *BoltState) addContainer(ctr *Container, pod *Pod) error {
if err != nil {
return err
}
defer db.Close()
defer s.closeDBCon(db)
err = db.Update(func(tx *bolt.Tx) error {
idsBucket, err := getIDBucket(tx)