Direct_stream_writer.t
is a simple object for responding to a Pipe_rpc
query.
Similar to implement
, but you are given the writer instead of providing a writer
and the writer is a Direct_stream_writer.t
instead of a Pipe.Writer.t
.
The main advantage of this interface is that it consumes far less memory per open query.
Though the implementation function is given a writer immediately, the result of the
client's call to dispatch
will not be determined until after the implementation
function returns. Elements written before the function returns will be queued up to
be written after the function returns.
This has (..., 'error) Result.t
as its return type to represent the possibility of
the call itself being somehow erroneous (but understood - the outer Or_error.t
encompasses failures of that nature). Note that this cannot be done simply by
making 'response
a result type, since ('response Pipe.Reader.t, 'error) Result.t
is distinct from ('response, 'error) Result.t Pipe.Reader.t
.
Closing the pipe has the effect of calling abort
.
Calling dispatch_iter t conn query ~f
is similar to calling dispatch t conn
query
and then iterating over the result pipe with f
. The main advantage it
offers is that its memory usage is much lower, making it more suitable for
situations where many queries are open at once.
f
may be fed any number of Update _
messages, followed by a single Closed _
message.
f
can cause the connection to stop reading messages off of its underlying
Reader.t
by returning Wait _
. This is the same as what happens when a client
stops reading from the pipe returned by dispatch
when the Pipe_rpc.t
has
client_pushes_back
set.
When successful, dispatch_iter
returns an Id.t
after the subscription is
started. This may be fed to abort
with the same Pipe_rpc.t
and Connection.t
as
the call to dispatch_iter
to cancel the subscription, which will fill in the
implementation's aborted
Deferred.t
. Calling it with a different Pipe_rpc.t
or
Connection.t
has undefined behavior.
abort rpc connection id
given an RPC and the id returned as part of a call to
dispatch, abort requests that the other side of the connection stop sending
updates.
close_reason metadata
will be determined sometime after the pipe associated with
metadata
is closed. Its value will indicate what caused the pipe to be closed.