Cowboy will set the socket's buffer size dynamically to
better fit the current workload. When the incoming data
is small, a low buffer size reduces the memory footprint
and improves responsiveness and therefore performance.
When the incoming data is large, such as large HTTP
request bodies, a larger buffer size helps us avoid
doing too many binary appends and related allocations.
Setting a large buffer size for all use cases is
sub-optimal because allocating more than needed
necessarily results in a performance hit (not just
increased memory usage).
By default Cowboy starts with a buffer size of 8192 bytes.
It then doubles or halves the buffer size depending on
the size of the data it receives from the socket. It
stops decreasing at 8192 and increasing at 131072 by
default.
To keep track of the size of the incoming data Cowboy
maintains a moving average. It allows Cowboy to avoid
changing the buffer too often but still react quickly
when necessary. Cowboy will increase the buffer size
when the moving average is above 90% of the current
buffer size, and decrease when the moving average is
below 40% of the current buffer size.
The current buffer size and moving average are
propagated when switching protocols. The dynamic buffer
is implemented in HTTP/1, HTTP/2 and HTTP/1 Websocket.
HTTP/2 Websocket has it disabled because it doesn't
interact directly with the socket; in that case it
is HTTP/2 that has a dynamic buffer.
The dynamic buffer provides a very large performance improvement
in many scenarios, at minimal cost for others. Because it largely
depend on the underlying protocol the improvements are no all equal.
TLS and compression also impact the results.
The improvement when reading a large request body, with the
requests repeated in a fast loop are:
* HTTP: 6x to 20x faster
* HTTPS: 2x to 6x faster
* H2: 4x to 5x faster
* H2C: 20x to 40x faster
I am not sure why H2C's performance was so bad, especially compared
to H2, when using default buffer sizes. Dynamic buffers make H2C a
lot more viable with default settings.
The performance impact on "hello world" type requests is minimal,
it goes from -5% to +5% roughly.
Websocket improvements vary again depending on the protocol, but
also depending on whether compression is enabled:
* HTTP echo: roughly 2x faster
* HTTP send: roughly 4x faster
* H2C echo: roughly 2x faster
* H2C send: 3x to 4x faster
In the echo test we reply back, and Gun doesn't have the dynamic
buffer optimisation, so that probably explains the x2 difference.
With compression however there isn't much improvement. The results
are roughly within -10% to +10% of each other. Zlib compression
seems to be a bottleneck, or at least to modify the performance
profile to such an extent that the size of the buffer does not
matter. This happens to randomly generated binary data as well
so it is probably not caused by the test data.
Before this commit frames could "cheat" by compressing data
below the limit which would get expanded above the limit.
Now Cowboy will stop decompressing data when the limit is
reached.
Following the same strategy as Websocket described in
commit cbed21c383e4cebb7df5a0a8b81f18c1738bef3e
Gains are comparable as far as Websocket over HTTP/2
is concerned.
`perf` has shown that Cowboy spends a lot of time
cancelling and starting this timer. Instead of resetting
for every data received, we now only reset a field in the
state.
Before it was working like this:
- start idle timeout timer
- on trigger, close the connection
- on data, cancel and start again
Now it's working like this:
- start idle timeout timer for a tenth of its duration, with tick number = 0
- on trigger, if tick number != 10
- start the timer again, again for a tenth of its duration
- increment tick number
- on trigger, if tick number = 10
- close the connection
- on data, set tick number to 0
It benchmarks binary, ascii, mixed and japanese data
using Websocket and Websocket over HTTP/2.
HTTP/2 options get set to ensure that performance is
better than the default HTTP/2 options.
It switches to Gun and Ranch branches that include
fixes that are required for tests to complete successfully.
This includes Websocket over HTTP/3.
Since quicer, which provides the QUIC implementation,
is a NIF, Cowboy cannot depend directly on it. In order
to enable QUIC and HTTP/3, users have to set the
COWBOY_QUICER environment variable:
export COWBOY_QUICER=1
In order to run the test suites, the same must be done
for Gun:
export GUN_QUICER=1
HTTP/3 support is currently not available on Windows
due to compilation issues of quicer which have yet to
be looked at or resolved.
HTTP/3 support is also unavailable on the upcoming
OTP-27 due to compilation errors in quicer dependencies.
Once resolved HTTP/3 should work on OTP-27.
Because of how QUIC currently works, it's possible
that streams that get reset after sending a response
do not receive that response. The test suite was
modified to accomodate for that. A future extension
to QUIC will allow us to gracefully reset streams.
This also updates Erlang.mk.
This is caused by the timeout being 1s after the period.
When the CI environment is overloaded, sometimes the
timeout will trigger. We retry, knowing that the
timetrap will catch us if we retry too much.
It is now tested both via cowboy_req:read_body and
via cowboy_req:cast.
Removes a bad example from the guide of body reading
with period of infinity, which does not work.
While we are identified as a supervisor in the tree,
we no longer manage children processes at that point,
so do not need to trap exit signals. Users can still
enable trap_exit if they prefer to.
We must add it even if we don't end up compressing because
it indicates that we might. This indication doesn't mean
that the user agent's accept-encoding values will ever
result in content encoding being applied.
The previous behavior was to accept them and drop the
content-length header as per the RFC recommendation.
But since this behavior is not normal it is safer to
just reject such requests than risk security issues.
In the cowboy_compress_h stream handler.
Otherwise this could cause issues with caching, with the
etag being the same for compressed/uncompressed content.
Users that wish to send etags AND compress will have to
do it manually for the time being.
The read buffer was changed into an iovec to avoid doing
too many binary concatenations and allocations.
Decompression happens transparently: when decoding gzip,
the content-encoding header is removed (we only decode
when "gzip" is the only encoding so nothing remains).
We always add a content_decoded key to the Req object.
This key contains a list of codings that were decoded,
in the reverse order in which they were. Currently it
can only be empty or contain <<"gzip">> but future
improvements or user handlers may see it contain more
values.
The option to disable decompression was renamed to
decompress_enabled and defaults to true.
It is no longer possible to enable/disable decompression
in the middle of reading the body: this ensures that the
data we pass forward is always valid.
Various smaller improvements were made to the code,
tests and manual pages.
A new option reset_idle_timeout_on_send has been added.
When set to 'true', the idle timeout is reset not only
when data is received, but also when data is sent.
This allows sending large responses without having to
worry about timeouts triggering.
The default is currently unchanged but might change in
a future release.
LH: Greatly reworked the implementation so that the
timeout gets reset on almost all socket writes.
This essentially completely supersets the original
work. Tests are mostly the same although I
refactored a bit to avoid test code duplication.
This commit also changes HTTP/2 behavior a little when
data is received: Cowboy will not attempt to update the
window before running stream handler commands to avoid
sending WINDOW_UPDATE frames twice. Now it has some
small heuristic to ensure they can only be sent once
at most.
The socket staying open meant that the graceful shut down
of the Cowboy listeners were waiting for the connections
to be closed gracefully (or a timeout). Closing explicitly
where it makes sense ensures we don't unnecessarily wait.
This commit removes a full minute in the run time of all
Cowboy test suites (minus examples).
Sending extra response prevented by terminating all streams except
the one currently executing.
LH: Reworded some variables to make what happens more obvious.
Doing so will let us notice when the connection is gone instead
of waiting for timeouts, at least in the cases where the remote
socket was closed properly. Timeouts are still needed in case
of TCP half-open problems.
This change means that the order of stream handler commands is
more important than before because socket errors may occur
during the processing of commands.
LH: I have fixed issues in the PR and incorporated changes
from a sister PR by @djankovic (git author: Dom J). I also
made sure the UTF-8 files were readable without Chinese
fonts and added their downloading to the examples test suite.
