# teacup_nats
A [Teacup](https://github.com/yuce/teacup.git) based Erlang client library for [NATS](http://nats.io/)
high performance messaging platform.
## NEWS
* **2016-04-16**: Version 0.3.5. This version fixes performance problems inroduced in version 0.3.3.
* **2016-04-07**: Version 0.3.4. New in this release:
* Rudimentary TLS/SSL support. Currently, this is auto-activated when the server
sends `tls_required => true` in an `INFO` message.
* **2016-04-03**: Released version 0.3.3. This release brings:
* Using [teacup 0.3.3](https://github.com/yuce/teacup/tree/0.3.3),
which boosts the performance by 50%.
* Implemented connect retry / reconnect strategy.
* Implemented message buffering.
* Sub and Unsub messages are queued.
* **2016-03-27**: You can check how the performance of **teacup_nats** compares to other NATS clients
[here](https://github.com/yuce/nats-client-benchmarks).
* **2016-03-19**: Initial release.
## Getting Started
**teacup_nats** requires Erlang/OTP 18.0+. It uses [rebar3](http://www.rebar3.org/)
as the build tool and is available on [hex.pm](https://hex.pm/). Just include the following
in your `rebar.config`:
```erlang
{deps, [teacup_nats]}.
```
**teacup_nats** depends on the `teacup` app to be started. Include it in your `.app.src` file:
```erlang
...
{applications,
[kernel,
stdlib,
teacup
]},
...
```
Or, start it manually:
```erlang
ok = application:start(teacup).
```
**rebar3** has a nice way of starting apps in the shell, you can try:
```
$ rebar3 shell --apps teacup
```
## TODO
* Clustering
## API
### Aysnchronous Connection
When using asycnhronous connections, you need to wait for a `{Conn, ready}`
message before publishing messages, subcribing to/unsubscribing from subjects.
* Connection functions:
* `tcnats:connect()`: Connect to the NATS server at address `127.0.0.1`, port `4222`,
* `tcnats:connect(Host :: binary(), Port :: integer())`: Connect to the NATS server
at `Host` and port `PORT`,
* `tcnats:connect(Host :: binary(), Port :: integer(), Opts :: map())`: Similar to
above, but also takes an `Opts` map. Currently usable keys:
* `verbose => true | false`: If `verbose == true`, NATS server
sends an acknowledgement message on `pub`, `sub`, `unsub` operations and
`connect` operation becomes synchronous.
* `user => User :: binary()`,
* `pass => Password :: binary()`,
* `buffer_size => MessageBufferSize :: non_neg_integer()`: The number of publish messages
to buffer before quitting. The default is 0. Setting `MesssageBufferSize` to
`infinity` enables unlimited buffering.
* `reconnect => {Interval :: non_neg_integer(), MaxRetry :: non_neg_integer()}`: Specifies
reconnect strategy. `Interval` is the time in milliseconds between retrials, and `MaxRetry` is
the number of retrials before quitting. You can set `MaxRetry` to `infinity` to try reconnecting
forever. The default is `{undefined, 0}`, "don't try to reconnect".
* Publish functions:
* `tcnats:pub(Conn :: teacup_ref(), Subject :: binary())`: Publish message with only
the subject,
* `tcnats:pub(Conn :: teacup_ref(), Subject :: binary()), Opts :: map()`: Publish message
the subject with `Options`. Valid options:
* `payload => Payload :: binary()`,
* `reply_to => Subject :: binary()`
* Subscribe functions:
* `tcnats:sub(Conn :: teacup_ref(), Subject :: binary())`: Subscribe to the `Subject`,
* `tcnats:sub(Conn :: teacup_ref(), Subject :: binary(), Opts :: map())`: Subscribe to the `Subject`, with
`Options`. Valid options:
* `queue_group => QGroup :: binary()`
* Unsubscribe functions:
* `tcnats:unsub(Conn :: teacup_ref(), Subject :: binary())`: Unsubscribe from `Subject`,
* `tcnats:unsub(Conn :: teacup_ref(), Subject :: binary(), Opts :: map())`: Unsubscribe from `Subject`, with
`Options`. Valid options:
* `max_messages => MaxMessages :: integer()`: Automatically unsubscribe after receiving `MaxMessages`.
#### Sample
```erlang
main() ->
% Connect to the NATS server
{ok, Conn} = tcnats:connect(<<"demo.nats.io">>, 4222),
% When the connection is OK to use, a `ready` message is sent, wait for it
ready_loop(Conn).
ready_loop(Conn) ->
receive
{Conn, ready} ->
% It's OK to use the connection now
% Publish some message
tcnats:pub(Conn, <<"teacup.control">>, #{payload => <<"start">>}),
% subscribe to some subject
tcnats:sub(Conn, <<"foo.*">>),
loop(Conn)
end.
loop(Conn) ->
receive
{Conn, {msg, Subject, _ReplyTo, Payload}} ->
% Do something with the received message
io:format("~p: ~p~n", [Subject, Payload]),
loop(Conn)
end.
```
### Synchronous Connection
In order to activate the synchronous mode, just pass `#{verbose => true` to `tcnats:connect`.
Connect, publish, subscribe and unsubscribe operations block and return either `ok` on
success or `{error, Reason :: term()}` on failure.
#### Sample
```erlang
main() ->
% Connect to the NATS server
{ok, Conn} = tcnats:connect(<<"demo.nats.io">>, 4222, #{verbose => true}),
% The connection is OK to use
% Publish some message
ok = tcnats:pub(Conn, <<"teacup.control">>, #{payload => <<"start">>}),
% subscribe to some subject
ok = tcnats:sub(Conn, <<"foo.*">>),
loop(Conn).
loop(Conn) ->
receive
{Conn, {msg, Subject, _ReplyTo, Payload}} ->
% Do something with the received message
io:format("~p: ~p~n", [Subject, Payload]),
loop(Conn)
end.
```
## License
```
Copyright (c) 2016, Yuce Tekol <yucetekol@gmail.com>.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* The names of its contributors may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
```
