pub struct ReleaseCapacity { /* fields omitted */ }
A handle to release window capacity to a remote stream.
This type allows the caller to manage inbound data flow control. The
caller is expected to call release_capacity
after dropping data frames.
Each stream has a window size. This window size is the maximum amount of
inbound data that can be in-flight. In-flight data is defined as data that
has been received, but not yet released.
When a stream is created, the window size is set to the connection's initial
window size value. When a data frame is received, the window size is then
decremented by size of the data frame before the data is provided to the
caller. As the caller finishes using the data, release_capacity
must be
called. This will then increment the window size again, allowing the peer to
send more data.
There is also a connection level window as well as the stream level window.
Received data counts against the connection level window as well and calls
to release_capacity
will also increment the connection level window.
WINDOW_UPDATE
frames will not be sent out for every call to
release_capacity
, as this would end up slowing down the protocol. Instead,
h2
waits until the window size is increased to a certain threshold and
then sends out a single WINDOW_UPDATE
frame representing all the calls to
release_capacity
since the last WINDOW_UPDATE
frame.
This essentially batches window updating.
Following is a basic scenario with an HTTP/2.0 connection containing a
single active stream.
- A new stream is activated. The receive window is initialized to 1024 (the
value of the initial window size for this connection).
- A
DATA
frame is received containing a payload of 400 bytes.
- The receive window size is reduced to 424 bytes.
release_capacity
is called with 200.
- The receive window size is now 624 bytes. The peer may send no more than
this.
- A
DATA
frame is received with a payload of 624 bytes.
- The window size is now 0 bytes. The peer may not send any more data.
release_capacity
is called with 1024.
- The receive window size is now 1024 bytes. The peer may now send more
data.
Returns the stream ID of the stream whose capacity will
be released by this ReleaseCapacity
.
If the lock on the stream store has been poisoned.
Release window capacity back to remote stream.
This releases capacity back to the stream level and the connection level
windows. Both window sizes will be increased by sz
.
See struct level documentation for more details.
This function panics if increasing the receive window size by sz
would
result in a window size greater than the target window size set by
set_target_window_size
. In other words, the caller cannot release
more capacity than data has been received. If 1024 bytes of data have
been received, at most 1024 bytes can be released.
Performs copy-assignment from source
. Read more
Formats the value using the given formatter. Read more
Creates owned data from borrowed data, usually by cloning. Read more
🔬 This is a nightly-only experimental API. (toowned_clone_into
)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
🔬 This is a nightly-only experimental API. (try_from
)
The type returned in the event of a conversion error.
🔬 This is a nightly-only experimental API. (try_from
)
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
🔬 This is a nightly-only experimental API. (try_from
)
The type returned in the event of a conversion error.
🔬 This is a nightly-only experimental API. (try_from
)
🔬 This is a nightly-only experimental API. (get_type_id
)
this method will likely be replaced by an associated static