CoreCache.transactionLookupAsync

Issue a transactional lookup into the cache without blocking, returning a PendingTransaction.

This behaves like CoreCache.transactionLookup() — the same request collapsing and revalidation semantics apply — except that the lookup itself does not block. Instead of returning a TransactionCacheEntry directly, it returns a PendingTransaction, which can be polled via PendingTransaction.prototype.pending, or resolved via PendingTransaction.prototype.wait, optionally bounded by a timeout.

Syntax

transactionLookupAsync(key, options)

Parameters

• key : string

  • A cache key which is a string with a length of up to 8,135 that identify a cached item.
  • The cache key may not uniquely identify an item; headers can be used to augment the key when multiple items are associated with the same key.

• options : object

  • headers : HeadersInit optional
    • The headers act as additional factors in object selection, and the choice of which headers to factor in is determined during insertion, via the vary property within TransactionInsertOptions.
    • A lookup will succeed when there is at least one cached item that matches lookup’s key, and all of the lookup’s headers included in the cache items’ vary list match the corresponding headers in that cached item.
    • A typical example is a cached HTTP response, where the request had an "Accept-Encoding" header. In that case, the origin server may or may not decide on a given encoding, and whether that same response is suitable for a request with a different (or missing) Accept-Encoding header is determined by whether Accept-Encoding is listed in Vary header in the origin’s response.
    • Note: These headers are narrowly useful for implementing cache lookups incorporating the semantics of the HTTP Vary header.

Return value

Returns an instance of PendingTransaction.

Exceptions

• TypeError
  • If the provided key:
    • Is an empty string
    • Cannot be coerced to a string
    • Is longer than 8135 characters