# ex_data_dog
[](https://travis-ci.org/KamilLelonek/ex-data-dog)
## Installation
If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `ex_data_dog` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[{:ex_data_dog, "~> 0.1.0"}]
end
```
Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/ex_data_dog](https://hexdocs.pm/ex_data_dog).
## Configuration
Configure `ex_data_dog` using `Mix.Config` as usual (probably in your `config/`):
```elixir
use Mix.Config
config :ex_data_dog,
host: "your.datadog.host.com",
port: 1234,
namespace: "your-app"
```
The defaults are:
* host: `127.0.0.1`
* port: `8125`
* namespace: `nil`
## API
### Counters
Counters can be manipulated with `ExDataDogTest.increment/1` and
`ExDataDogTest.decrement/1` for simple counts:
```elixir
if passed? do
ExDataDogTest.increment("cases.passed")
end
```
```elixir
if cancelled_account? do
ExDataDogTest.decrement("users")
end
```
You can also provide a `sample_rate` with `ExDataDogTest.increment/2` and
`ExDataDogTest.decrement/2`. For example, in this case an increment for
`cart.added` will only be sent 50% of the time:
```elixir
ExDataDogTest.increment("cart.added", sample_rate: 0.5)
```
To set a counter explicitly, use `ExDataDogTest.counter/2`:
```elixir
ExDataDogTest.counter(3, "cart.removed")
```
You can also send a `sample_rate`:
```elixir
ExDataDogTest.counter(3, "cart.removed", sample_rate: 0.25)
```
Note that the function returns the value (eg, `3` here), making it
suitable for pipelining.
### Timers
Manually timed values can be recorded with `ExDataDogTest.timer/2`:
```elixir
elapsed_ms = # something manually timed in
ExDataDogTest.timer(elapsed_ms, "foobar")
```
The value passed to `ExDataDogTest.timer/2` (eg, `elapsed_ms` here) is
returned from it, making this suitable for pipelining.
For convenience, you can also time a function call with
`ExDataDogTest.timing/2`:
```elixir
ExDataDogTest.timing("foo.bar", fn ->
# Time something
end)
```
To sample (ie, 50% of the time), pass a `sample_rate`:
```elixir
ExDataDogTest.timing("foo.bar", fn ->
# Time something, some of the time
end, sample_rate: 0.5)
```
Note that, regardless of the sample rate, the function is always
called -- it's just not always measured. Also note that the return
value of the measured function is returned, making this suitable for pipelining.
### Sets
A value can be recorded in a set with `ExDataDogTest.set/2`:
```elixir
ExDataDogTest.set(user_id, "users")
```
Note that the function returns the value, making it suitable for pipelining.
####Tags
All metrics support the
[Datadog-specific tags extension](http://docs.datadoghq.com/guides/dogstatsd/#tags)
so you may provide a `tags` option, eg:
```elixir
ExDataDogTest.increment("cart.added", tags: ~w(foo bar))
```
### Histograms
The [histogram](http://docs.datadoghq.com/guides/dogstatsd/#histograms) extension is supported as well:
```elixir
ExDataDogTest.histogram(42, "database.query.time", tags: ["db", "perf"])
```
Note that the function returns the value, making it suitable for pipelining.
### Histogram Timing
A histogram version of the [ExDataDogTest.timing](#timers) function is also supported:
```elixir
ExDataDogTest.histogram_timing("foo.bar", fn ->
# Time something
end)
```
## Decorators
The decorators allow you to quickly and easily time function calls in
your code. Simply replace `def` with `deftimed` for those functions
you wish to time.
```elixir
defmodule MyModule.Data do
use ExDataDog.Decorator
deftimed slow_function do
# This is a suspect function we wish to time.
end
end
```
Now all calls to `MyModule.Data.slow_function/0` will be timed and
reported to your statsd server. By default the metric key used for
each call will be `PREFIX.function_call.MODULE.FUNCTION_ARITY`. So in
this example it would have been `function_call.mymodule.data.slow_function_0`.
You can change the metric name by setting the `@metric` attribute
ahead of the function. The metric will apply to other function
definitions of the same arity unless specifically changed again. Other
following functions of different name or arity will use the default.
```elixir
deftimed init, do: nil # PREFIX.function_call.mymodule.data.init_0
@metric "trace.some_function"
deftimed some_function(1), do: nil # PREFIX.trace.some_function
deftimed some_function(2), do: nil # PREFIX.trace.some_function
@metric "trace.some_function_catchall"
deftimed some_function(x) when is_list(x), do: nil # PREFIX.trace.some_function_catchall
deftimed some_function(x), do: nil # PREFIX.trace.some_function_catchall
deftimed some_function(x,y), do: nil # PREFIX.function_call.mymodule.data.some_function_2
```
You can set options using the `@metric_options` attribute. This follows the same rules as with the `@metric` example abobe.
Here we use Datadog's "tag" extension to StatD:
```elixir
@metric_options [tags: ["basic"]]
deftimed some_function(), do: nil
```
There are 2 global options available. Both will apply to all functions that follow it unless locally overridden.
* `@default_metric_options`: Metric options to use unless overridden with `@metric_options`. Defaults to [].
* `@use_histogram`: Send results using histograms instead of gauges. Defaults to false.
