nim-nats is a Nim wrapper for the nats.c library.

nim-nats is distributed as a Nimble package. nats.nim wrapper is generated with nimgen and c2nim.

nim-nats may be linked with dynamic nats.c lib which must be installed on the system and be available at runtime. You can link statically as well with nim c --passL:'-L/usr/local/lib -lnats_static' yourcode.nim. On Mac OS X you can easily install lib with brew install cnats

Latest nim-nats version 3.x should work with NATS client library nats.c 3.x

JetStream and Key-Value is not yet wrapped, but might be soon.

Installation

nim-nats can be installed via Nimble:

nimble install nats

You can also install from the github repo:

 git clone https://github.com/deem0n/nim-nats
 cd nim-nats
 nimble install -y

This will download and install nim-nats in the standard Nimble package location, typically ~/.nimble. Once installed, it can be imported into any Nim program.

Usage

Check nimtest.nim for example usage.

Module documentation can be found here.

Don't forget to import nats in your code:

import nats

Hint: On Linux you may get problems linking your app and see errors like this:

/usr/local/lib64/libnats.so: undefined symbol: protobuf_c_empty_string
could not load: libnats.so

It happens if your system protobuf_c lib is outdated. For example, CentOS 7 has protobuf_c 1.0.x while current version is 1.3.x. It seems that recent cnats wants recent protobuf, which is not available on recent Linux distros, ops. To avoid dll hell I recomend to statically link against libnats_static.a (which is installed by default by nats.c). But to make that possible you will need to compile static version of protobuf_c.a or pick it up from cnats distribution.

# wget protobuf-cpp-3.6.1.tar.gz
cd protobuf-3.6.1
./configure --disable-shared --prefix=/opt
make && make install

# wget protobuf-c-1.3.1.tar.gz
cd protobuf-c-1.3.1
PKG_CONFIG_PATH=/opt/lib/pkgconfig ./configure --prefix=/opt
make && make install

You can add static task to your project .nimble file like this:

task static, "builds a static app":
  if buildOS == "linux":
    echo "Assuming that /opt/lib/libprotobuf-c.a is present..."
    exec "nimble -y build --dynlibOverride:nats --passL:-L/usr/local/lib64 --passL:-lnats_static --passL:-lpthread --passL:/opt/lib/libprotobuf-c.a --passL:-lssl --passL:-lcrypto"
  elif buildOS == "macosx":
    exec "nimble -y build --dynlibOverride:nats --passL:-L/usr/local/lib --passL:-lnats_static"

Run nimble static to build a version of your app which will not depend on cnats and protobuf libs installed on the target host.

Testing

 git clone https://github.com/deem0n/nim-nats
 cd nim-nats
 nimble test

nimble test will start nats-server server on port 12345 and run the test client app which will publish and recieve messages to/from NATS subject. nats-sewrver will be killed after test completion. Please note, that test code will run on Mac OS X and Linux only, but I happily accept PR to fix Windows.

Development

You will need latest nimgen, which is not released. Also I probably will migrate to the nimterop one day. For now you can try to run nimble setup, which will download some nats.c headers from github and will run nimgen to convert headers to nim.

 nimble install nimgen@#HEAD
 git clone https://github.com/deem0n/nim-nats
 cd nim-nats
 nimble setup
 nimble test

Credits

nim-nats wraps the cnats source code and all licensing terms of nats.c apply to the usage of this package. cnats is licensed under Apache 2.0. All other code (i.e tests) in this repo is licensed under MIT license.

Credits go out to c2nim and to nimgen as well without which this package would be greatly limited in its abilities.

Future plans

1. Add JetStream NATS API
2. Add KV
3. More tests
4. Examples of async API with callbacks (requires event loop on the nim side)

Feedback

nim-nats is a work in progress and any feedback or suggestions are welcome. It is hosted on GitHub with a MIT license so issues, forks and PRs are most appreciated.