ExInsights

Elixir client library to log telemetry data on Azure Application Insights.

Installation

Install from hex by adding ex_insights to your list of dependencies in mix.exs:

def deps do
  [
    {:ex_insights, "~> 0.3"}
  ]
end

Note:

The library is packaged as an application. In elixir <= 1.3.x you will need to add it explicitly to the list of applications started before your own inside mix.exs like this:

# This step is only required for older elixir installations
def application do
  [
    applications: [:ex_insights]
  ]
end

Configuration

Instrumentation key

You need at the very least to set your instrumentation key in order to start accepting telemetry requests on azure. You can do this by setting the instrumentation_key property like this:

config :ex_insights,
  instrumentation_key: "0000-1111-2222-3333"

You can also use an environment variable instead if that's your preference

config :ex_insights,
  instrumentation_key: {:system, "INSTRUMENTATION_KEY"}
# at runtime the application will look for the INSTRUMENTATION_KEY environment variable

If you forget to set the key the application will raise with an appropriate message anytime an ExInsights.track_xxx function is used.

Flush interval

You can also set the flush interval in seconds (ie the interval at which data will be sent over to azure). The default is 30 seconds.

config :ex_insights,
  flush_interval_secs: 30

Usage

Basic Usage

All public tracking methods are under the ExInsights module. Examples:

# will post a click custom_event to azure
ExInsights.track_event("click")

# with custom defined property "type" and measurement "count"
ExInsights.track_event("click", %{type: "button"}, %{count: 2})

# send custom metric data. Does not support aggregated data (count/stdDev, min, max)
ExInsights.track_metric("bananas", 10)

# log arbitrary data
ExInsights.track_trace("1-2-3 boom", :warning)

# log time taken for requests to external resources, eg. database or http service calls
ExInsights.track_dependency("get_user_balance", "http://my.api/get_balance/aviator1", 1500, true, "user", "my.api")

For more details and optional arguments look at the ExInsights module documentation.

Advanced usage

Even though you can call ExInsights.track_xxx methods directly, the recommended way to use the library is by decorating methods you need to track using decorators.

# Make sure to add the following line before using any decorators
use ExInsights.Decoration.Attributes

# add the @decorate track_xxx() attribute right above each function you need to track

@decorate track_event() # will log the "update_user_email" event in AppInsights on funtion entry
def update_user_email(email, user) do
  # ...
end

@decorate track_dependency("user-actions") # put under dependency type:user-actions in AppInsights UI
def login_user(user) do
  # ... maybe call external api here
end

@decorate track_exception() # will track errors and exits
def dangerous_stuff do
  # ... do work that may fail
end

Inner workings

• Calling any tracking function ExInsights.track_xxx from your code will not immediately send the data to Azure. It will instead be aggregated in memory until the flush_timer is triggered (every 30 secs, configurable) and the data will be batch sent.
• When the application shuts down it will attempt to flush any remaining data.
• If you are behind a firewall (usually happens in production deployments) make sure your network rules allow HTTP POSTs to https://dc.services.visualstudio.com
• If requests to azure tracking services fail (network or server errors or bad requests) you will not be alerted.
• track_dependency and track_exception decorators will try to rescue/catch any errors (and log those) and then reraise the error / exit as appropriate. This is a different (but hopefully working) approach than what the AppSignal guys do (a separate process monitoring crashes)