FLUSH(5) FLUSH(5)
NAME
flush - abort a message
SYNOPSIS
Tflush tag[2] oldtag[2]
Rflush tag[2]
DESCRIPTION
When the response to a request is no longer needed, such as
when a user interrupts a process doing a read(2), a Tflush
request is sent to the server to purge the pending response.
The message being flushed is identified by oldtag. The
semantics of flush depends on messages arriving in order.
The server must answer the flush message immediately. If it
recognizes oldtag as the tag of a pending transaction, it
should abort any pending response and discard that tag. In
either case, it should respond with an Rflush echoing the
tag (not oldtag) of the Tflush message. A Tflush can never
be responded to by an Rerror message.
When the client sends a Tflush, it must wait to receive the
corresponding Rflush before reusing oldtag for subsequent
messages. If a response to the flushed request is received
before the Rflush, the transaction is considered to have
finished, and should be treated as though it had not been
flushed. If no response is received before the Rflush, the
flushed transaction is considered to have been canceled, and
should be treated as though it had never been sent.
Several exceptional conditions are handled correctly by the
above specification: sending multiple flushes for a single
tag, flushing a Tflush, and flushing an invalid tag.
Page 1 Plan 9 (printed 4/20/24)