{"version":"2.1.223","anchor":"compare-and-swap-retry-helper-for-versioned-storage-keys","canonical_anchor":"compare-and-swap-retry-helper-for-versioned-storage-keys","heading":"Compare-and-swap retry helper for versioned storage keys","tier":"internal","area":"Storage Backend","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.223\/e\/compare-and-swap-retry-helper-for-versioned-storage-keys","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.223","markdown":"### Compare-and-swap retry helper for versioned storage keys\n\nInternal plumbing lets concurrent writers update shared state without clobbering each other.\n\n**What**\n\nAn internal helper read-modify-writes a storage key with `ifMatch`\/`ifAbsent` preconditions and retries with backoff when the precondition fails, so concurrent writers do not clobber each other.\n\n**Details**\n\n- retries on `PreconditionFailed` and `AlreadyExists` with backoff\n- refuses keys whose namespace is classified 'plain' (last-writer-wins) and returns an `InvalidArgument` error naming the offending argument\n- a new namespace-discipline classifier marks `task`, `team`, `identity` and plain `globalConfig` as versioned; settings, memory, cache, state, job and userConfigDir are plain\n\n**Evidence**\n\n`casRetry arbitrates versioned keys only`\n\n- Area: Storage Backend\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 2\/5\n- Present in the build but not switched on"}