Tapper v0.2.0 Tapper.Application

Tapper main application; configures and starts application supervisor.

Add :tapper to your application’s mix.exs:

# Configuration for the OTP application.
#
# Type `mix help compile.app` for more information.
def application do
  [mod: {MyApp, []},
   applications: [
     :tapper
     # other applications
    ]]
end

Configuration

Looks for configuration under :tapper key:

key	type	purpose
`system_id`	String.t	This application’s id; used for `service_name` in default `Endpoint` used in annotations; default `unknown`
`ip`	tuple	This application’s principle IPV4 or IPV6 address, as 4- or 8-tuple of ints; defaults to IP of first non-loopback interface, or `{127.0.0.1}` if none.
`port`	integer	The application’s principle port, e.g. HTTP port 80; defaults to 0
`reporter`	atom	Module implementing `Tapper.Reporter.Api` to use for reporting spans, defaults to `Tapper.Reporter.Console`.

All keys support the Phoenix-style {:system, var} format, to allow lookup from shell environment variables, e.g. {:system, "PORT"} to read PORT environment variable.

Config values will be converted to the expected type, principally so that string values can be handled from environment variables:

ip is expected in dotted IPV4 or colon IPV6 notation, see Erlang’s inet:parse_address/1
reporter can be specified as a string which will be converted to an atom, following Elixir’s module name rules.

Example

In config.exs etc.:

config :tapper,
  system_id: "my-cool-svc",
  reporter: Tapper.Reporter.Zipkin,
  port: {:system, "PORT"}

Summary

Functions

start(type, args)

Called when an application is started

Functions

start(type, args)

Called when an application is started.

This function is called when an the application is started using Application.start/2 (and functions on top of that, such as Application.ensure_started/2). This function should start the top-level process of the application (which should be the top supervisor of the application’s supervision tree if the application follows the OTP design principles around supervision).

start_type defines how the application is started:

:normal - used if the startup is a normal startup or if the application is distributed and is started on the current node because of a failover from another mode and the application specification key :start_phases is :undefined.
{:takeover, node} - used if the application is distributed and is started on the current node because of a failover on the node node.
{:failover, node} - used if the application is distributed and is started on the current node because of a failover on node node, and the application specification key :start_phases is not :undefined.

start_args are the arguments passed to the application in the :mod specification key (e.g., mod: {MyApp, [:my_args]}).

This function should either return {:ok, pid} or {:ok, pid, state} if startup is successful. pid should be the PID of the top supervisor. state can be an arbitrary term, and if omitted will default to []; if the application is later stopped, state is passed to the stop/1 callback (see the documentation for the c:stop/1 callback for more information).

use Application provides no default implementation for the start/2 callback.

Callback implementation for Application.start/2.