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-rw-r--r--pkg/database/locks.go50
-rw-r--r--pkg/database/sql/000_init.sql3
-rw-r--r--pkg/database/states.go34
3 files changed, 76 insertions, 11 deletions
diff --git a/pkg/database/locks.go b/pkg/database/locks.go
new file mode 100644
index 0000000..53c6f6e
--- /dev/null
+++ b/pkg/database/locks.go
@@ -0,0 +1,50 @@
+package database
+
+import (
+ "encoding/json"
+)
+
+// Atomically check if there is an existing lock in place on the state. Returns
+// true if it can be set, otherwise returns false and lock is set to the value
+// of the existing lock
+func (db *DB) SetLockOrGetExistingLock(name string, lock any) (bool, error) {
+ tx, err := db.Begin()
+ if err != nil {
+ return false, err
+ }
+ defer func() {
+ if err != nil {
+ _ = tx.Rollback()
+ }
+ }()
+ var data []byte
+ if err = tx.QueryRowContext(db.ctx, `SELECT lock FROM states WHERE name = ?;`, name).Scan(&data); err != nil {
+ return false, err
+ }
+ if data != nil {
+ err = json.Unmarshal(data, lock)
+ return false, err
+ }
+ if data, err = json.Marshal(lock); err != nil {
+ return false, err
+ }
+ _, err = tx.Exec(`UPDATE states SET lock = json(?) WHERE name = ?;`, data, name)
+ if err != nil {
+ return false, err
+ }
+ err = tx.Commit()
+ return true, err
+}
+
+func (db *DB) Unlock(name, lock any) (bool, error) {
+ data, err := json.Marshal(lock)
+ if err != nil {
+ return false, err
+ }
+ result, err := db.Exec(`UPDATE states SET lock = NULL WHERE name = ? and lock = json(?);`, name, data)
+ if err != nil {
+ return false, err
+ }
+ n, err := result.RowsAffected()
+ return n == 1, err
+}
diff --git a/pkg/database/sql/000_init.sql b/pkg/database/sql/000_init.sql
index 0248896..6ec2ef7 100644
--- a/pkg/database/sql/000_init.sql
+++ b/pkg/database/sql/000_init.sql
@@ -5,6 +5,7 @@ CREATE TABLE schema_version (
CREATE TABLE states (
id INTEGER PRIMARY KEY,
name TEXT NOT NULL,
- data BLOB NOT NULL
+ data BLOB NOT NULL,
+ lock TEXT
) STRICT;
CREATE UNIQUE INDEX states_name on states(name);
diff --git a/pkg/database/states.go b/pkg/database/states.go
index 3a0b0b9..e848924 100644
--- a/pkg/database/states.go
+++ b/pkg/database/states.go
@@ -2,6 +2,7 @@ package database
import (
"database/sql"
+ "fmt"
)
func (db *DB) DeleteState(name string) error {
@@ -18,18 +19,31 @@ func (db *DB) GetState(name string) ([]byte, error) {
return db.dataEncryptionKey.DecryptAES256(encryptedData)
}
-func (db *DB) SetState(name string, data []byte) error {
+// returns true in case of id mismatch
+func (db *DB) SetState(name string, data []byte, id string) (bool, error) {
encryptedData, err := db.dataEncryptionKey.EncryptAES256(data)
if err != nil {
- return err
+ return false, err
}
- _, err = db.Exec(
- `INSERT INTO states(name, data) VALUES (:name, :data) ON CONFLICT DO UPDATE SET data = :data WHERE name = :name;`,
- sql.Named("data", encryptedData),
- sql.Named("name", name),
- )
- if err != nil {
- return err
+ if id == "" {
+ _, err = db.Exec(
+ `INSERT INTO states(name, data) VALUES (:name, :data) ON CONFLICT DO UPDATE SET data = :data WHERE name = :name;`,
+ sql.Named("data", encryptedData),
+ sql.Named("name", name),
+ )
+ return false, err
+ } else {
+ result, err := db.Exec(`UPDATE states SET data = ? WHERE name = ? and lock->>'ID' = ?;`, encryptedData, name, id)
+ if err != nil {
+ return false, err
+ }
+ n, err := result.RowsAffected()
+ if err != nil {
+ return false, err
+ }
+ if n != 1 {
+ return true, fmt.Errorf("failed to update state, lock ID does not match")
+ }
+ return false, nil
}
- return nil
}