Cache.transact()

A write transaction, for with cache.transact() as tx:.

Usage

Source

Cache.transact(retry=False)

tx is the cache itself. On the thread that entered the block, every call on this cache directory inside it, through any handle, runs in the transaction: it commits when the block exits and rolls back if the block raises. Other threads’ and processes’ writes wait for it. Entered on a thread that already holds a transaction on this directory, it joins that one: the inner block’s exit doesn’t commit, and an exception the caller catches inside doesn’t undo the inner block’s writes.

A transaction belongs to a thread, not an asyncio task: another coroutine’s writes on the same thread during an await inside the block join it and roll back with it.

A block that exits with no exception but didn’t commit (another thread ended it, or it was rolled back after an error inside it) raises TransactionAborted at its exit, so it never exits cleanly when its writes are gone.

Parameters

retry: bool = False

Keep trying to begin while it times out, instead of raising Timeout. Never retries TransactionBusy. Each attempt waits up to timeout.

Raises

TypeError

retry isn’t a bool.

Examples

with cache.transact() as tx:     # all three land together, or none do
    tx.incr('requests')
    tx.incr(f'requests:{path}')
    tx.set('last_request', now)