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A nats client in pure elixir. Resilience, Performance, Ease-of-Use.
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README.md
[](https://travis-ci.org/mmmries/gnat)
# Gnat
A [nats.io](https://nats.io/) client for elixir.
The goals of the project are resiliency, performance, and ease of use.
## Usage
```elixir
{:ok, gnat} = Gnat.start_link(%{host: '127.0.0.1', port: 4222})
# Or if the server requires TLS you can start a connection with:
# {:ok, gnat} = Gnat.start_link(%{host: '127.0.0.1', port: 4222, tls: true})
{:ok, subscription} = Gnat.sub(gnat, self(), "pawnee.*")
:ok = Gnat.pub(gnat, "pawnee.news", "Leslie Knope recalled from city council (Jammed)")
receive do
{:msg, %{body: body, topic: "pawnee.news", reply_to: nil}} ->
IO.puts(body)
end
```
## Benchmarks
Part of the motivation for building this library is to get better performance.
To this end I've started a `bench.exs` script that we can use to check our performance.
As of this commit the most recent numbers from running on my macbook pro are:
| | ips | average | deviation | median |
| - | --- | ------- | --------- | ------ |
| parse-128 | 81.86 K | 12.22 μs | ±177.12% | 11.00 μs |
| pub - 128 | 146.22 K | 6.84 μs | ±450.03% | 6.00 μs |
| sub-unsub-pub16 | 9.06 K | 110.37 μs | ±68.61% | 102.00 μs |
| req-reply-4 | 5.67 K | 176.45 μs | ±19.81% | 165.00 μs |
These benchmarks all show single-actor performance with a locally running gnats server.
Running 32 client actors on an 8-core ubuntu server sending requests to another 8-core ubuntu server running 2 gnat subscriber actors we achieved:
* 19,920 requests/sec
* 90th % latency of 2.2ms
[see details in the performance issue](https://github.com/mmmries/gnat/issues/28)
## Development
Before running the tests make sure you have a locally running copy of `gnatsd` (`brew install gnatsd`).
We currently use version `1.3.0` in CI, but anything higher than `0.9.6` should be fine.
The typical `mix test` will run all the basic unit tests.
You can also run the `multi_server` set of tests that test connectivity to different
`gnatsd` configurations. You can run these with `mix test --only multi_server`.
The tests will tell you how to start the different configurations.
There are also some property-based tests that generate a lot of test cases.
You can tune how many test cases by setting the environment variable `N=200 mix test --only property` (default it 100).
For more details you can look at how Travis runs these things in the CI flow.