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Mobius

Library for localized telemetry metrics

installation

Installation

def deps do
  [
    {:mobius, "~> 0.5.0"}
  ]
end

usage

Usage

Add Mobius to your supervision tree and pass in the metrics you want to track.

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

quick-tips

Quick tips

To see a view of the current metrics you can use Mobius.info/0:

iex> Mobius.info()
Metric Name: vm.memory.total
Tags: %{}
last_value: 83952736

To plot a metric measurement over time you can use: Mobius.Exports.plot/4:

iex> Mobius.Exports.plot("vm.memory.total", :last_value, %{})
                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 

configure-persistence-directory

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:


children = [
   # ... other children ...
   {Mobius, metrics: metrics(), persistence_dir: "/tmp"}
   # ... other children ...
]

def metrics() do
  [
    Metrics.last_value("vm.memory.total", unit: {:byte, :kilobyte})
  ]
end

saving-autosaving-metrics-data

Saving / Autosaving metrics data

By default the metrics data is persisted on a normal shutdown. However, data will not be persisted during a sudden shutdown, eg Control-C in IEX, kill, sudden power off.

It's possible to manually call Mobius.save/1 to force an interim write of the persistence data.

This can be automated by passing autosave_interval to Mobius

def start(_type, _args) do
  metrics = [
    Metrics.last_value("my.telemetry.event"),
  ]

  children = [
    # ... other children ....
    {Mobius, metrics: metrics, autosave_interval: 60} # auto save every 60 seconds
    # ... 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

exporting-data

Exporting data

The Mobius.Exports module provide functions for exporting the data in a couple different formats.

  1. CSV
  2. Series
  3. Line plot
  4. Mobius Binary Format
# export as CSV string
Mobius.Exports.csv("vm.memory.total", :last_value, %{})

# export as series list
Mobius.Exports.series("vm.memory.total", :last_value, %{})

# export as mobius binary format
Mobius.Exports.mbf()

The Mobius Binary Format (MBF) is a binary string that has encoded and compressed the all the historical metrics that mobius current has. This is most useful for preparing metrics to send off to another system. To parse the binary format you can use Mobius.Exports.parse_mbf/1.

For each of these you can see the Mobius.Exports module for more details.

report-metrics-to-a-remote-server

Report metrics to a remote server

Mobius allows sending metrics to a remote server. You can do this by passing the :remote_reporter option to Mobius. This is a module that implements the Mobius.RemoteReporter behaviour. Optionally, you can pass the :remote_report_interval option to specify how often to report metrics, by default this is every 1 minute.