# Mobius
[](https://circleci.com/gh/mattludwigs/mobius/tree/main)
Library for localized telemetry metrics
## Installation
```elixir
def deps do
[
{:mobius, "~> 0.3.0"}
]
end
```
## Usage
Add `Mobius` to your supervision tree and pass in the metrics you want to track.
```elixir
def start(_type, _args) do
metrics = [
Metrics.last_value("my.telemetry.event"),
]
children = [
# ... other children ....
{Mobius, metrics: metrics}
# ... other children ....
]
# See https://hexdocs.pm/elixir/Supervisor.html
# for other strategies and supported options
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)
end
```
### Configure persistence directory
By default Mobius will try to save metric data for all resolutions and the
current value when the erlang system exists gracefully. This makes Mobius useful
for Nerves devices that have to reboot after doing a planned firmware update.
The default direction Mobius will try to persist data to is the `/data`
directory as this is friendly to Nerves devices. If you want Mobius to store
data in a different location you can pass that into Mobius when you start it:
```elixir
children = [
# ... other children ...
{Mobius, metrics: metrics, persistence_dir: "/tmp"}
# ... other children ...
]
```
### Charting historical metrics
Mobius tracks metrics overtime in a circular buffer and allows you to graph
metric values over time using `Mobius.Charts.plot/3`:
```
iex> Mobius.Charts.plot("vm.memory.total")
Metric Name: vm.memory.total, Tags: %{}
34355808.00 ┤
34253736.73 ┤ ╭──╮ ╭────╮
34151665.45 ┤ ╭────╯ ╰────╯ ╰───
34049594.18 ┤ ╭────╮ ╭────╮ ╭────╯
33947522.91 ┤ │ ╰────╯ ╰─╯
33845451.64 ┤ │
33743380.36 ┤ ╭────╯
33641309.09 ┤ │
33539237.82 ┤ │
33437166.55 ┤ │
33335095.27 ┼────╯
```
### Printing current metrics
To see the current metrics you can use `Mobius.Charts.info/0`:
```
iex> Mobius.Charts.info()
Event: vintage_net_qmi.connection.end.duration
Tags: %{ifname: "wwan0", status: :lan}
counter: 4
last_value: 310000
Event: vm.memory.total
Tags: %{}
last_value: 34674312
```
