fix(waku_archive): only allow a single instance to execute migrations (#2736)

waku/waku_archive/driver/postgres_driver/migrations.nim

@@ -72,6 +72,16 @@ proc migrate*(
   # Load migration scripts
   let scripts = pg_migration_manager.getMigrationScripts(currentVersion, targetVersion)
 
+  # Lock the db
+  (await driver.acquireDatabaseLock()).isOkOr:
+    error "failed to acquire lock", error = error
+    return err("failed to lock the db")
+
+  defer:
+    (await driver.releaseDatabaseLock()).isOkOr:
+      error "failed to release lock", error = error
+      return err("failed to unlock the db.")
+
   # Run the migration scripts
   for script in scripts:
     for statement in script.breakIntoStatements():

waku/waku_archive/driver/postgres_driver/postgres_driver.nim

@@ -853,6 +853,42 @@ proc sleep*(
 
   return ok()
 
+proc acquireDatabaseLock*(
+    s: PostgresDriver, lockId: int = 841886
+): Future[ArchiveDriverResult[void]] {.async.} =
+  ## Acquire an advisory lock (useful to avoid more than one application running migrations at the same time)
+  let locked = (
+    await s.getStr(
+      fmt"""
+    SELECT pg_try_advisory_lock({lockId})
+    """
+    )
+  ).valueOr:
+    return err("error acquiring a lock: " & error)
+
+  if locked == "f":
+    return err("another waku instance is currently executing a migration")
+
+  return ok()
+
+proc releaseDatabaseLock*(
+    s: PostgresDriver, lockId: int = 841886
+): Future[ArchiveDriverResult[void]] {.async.} =
+  ## Acquire an advisory lock (useful to avoid more than one application running migrations at the same time)
+  let unlocked = (
+    await s.getStr(
+      fmt"""
+    SELECT pg_advisory_unlock({lockId})
+    """
+    )
+  ).valueOr:
+    return err("error releasing a lock: " & error)
+
+  if unlocked == "f":
+    return err("could not release advisory lock")
+
+  return ok()
+
 proc performWriteQuery*(
     s: PostgresDriver, query: string
 ): Future[ArchiveDriverResult[void]] {.async.} =