This library is not under continuous maintenance; if you'd like to perform maintenance yourself, feel free to open an issue requesting access.
backwater allows you to call remote modules without depending on the
Erlang distribution protocol.
It's targeted at scenarios where nodes in one datacenter need to call nodes in another datacenter, over unsecure or unstable networks.
Run make shell to bring up a shell. We're going to expose the
string module and call it remotely.
Secret = crypto:strong_rand_bytes(32).backwater:start_clear_server(Secret, [string]).
% {ok, _ServerPid}backwater:call({"127.0.0.1", Secret}, string, to_upper, ["hello"]).
% {ok, "HELLO"}backwater is built on top of
cowboy and
hackney.
- Erlang/OTP 22 or higher
- rebar3
Documentation is hosted on HexDocs.
All requests and responses are authenticated and signed using a modified version of HTTP signatures; nevertheless, it's strongly recommended to use HTTPS, as HTTP signatures offer no protection against replay attacks - besides risking exposure of sensitive data.
By default, remote exceptions are returned as errors on the caller's
side. This behaviour can be tweaked using the
rethrow_remote_exceptions flag in :call/5 options.
Remote stack traces are returned by default. Because they are
computationally expensive to generate, this behaviour can be can be
changed using the return_exception_stacktraces flag in
:start_clear_server / :start_tls_server backwater options.
The external term format is used for all function arguments and return values.
Because trust is assumed unless declared otherwise (like in regular Erlang clusters), unsafe terms are decoded by default.
For function arguments, this behaviour can be tweaked through the
decode_unsafe_terms setting in backwater options when running
:start_clear_server or :start_tls_server.
For return values, this behaviour can be tweaked through the
decode_unsafe_terms setting in :call/5 options.
By default, both serialised function arguments and serialised return values larger than 300 bytes are subject to attempted compression using gzip. The actual compression result is only used if it is indeed smaller than the original payload.
For function arguments, this threshold can be tweaked through the
compression_threshold setting in :call/5 options.
For return values, this threshold can be tweaked through the
compression_threshold setting in backwater options when running
:start_clear_server or :start_tls_server.
By default, both serialised function arguments and serialised return values larger than 8 MiB are rejected (independently of whether they're transmitted in compressed form or not.)
For function arguments, this limit (in bytes) can be adjusted using the
max_encoded_args_size setting in backwater options when running
:start_clear_server or :start_tls_server.
For return values, this limit (in bytes) can be adjusted using the
max_encoded_result_size setting in :call/5 options.
The default listen port for HTTP is 8080; for HTTPS, it's 8443. This can
be adjusted on server using the http options, and on clients by
specifying it in Endpoint.
The client enforces a default connection timeout of 8s, and a receive
timeout of 5s. Either can be adjusted using either connect_timeout or
recv_timeout, respectively, in :call/5 options.
The server enforces a default receive timeout of 5s. This can be
adjusted using the recv_timeout setting in backwater options, when
running :start_clear_server or :start_tls_server.
For now, the best way to achieve this is to build requests using the
backwater_request module and interpret responses using the
backwater_response module.
MIT License
Copyright (c) 2017-2022 Guilherme Andrade
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.