Merge pull request #1 from Recruitee/dependencies_checks_configuration

Improve dependencies checks configuration

README.md

@@ -4,13 +4,15 @@ Asynchronous dependency health checks library.
 
 ## Features
 * User defined dependencies checks with flexible settings.
-* Dependencies checks functions are executed asynchronously as isolated processes.
+* Dependencies checks functions are executed asynchronously.
 * Built-in `Plug` module providing customizable response for a http health-check endpoint.
-* Checks states are stored in an ETS table, which means practically unlimited requests per second
-  processing capacity.
+* Support for multiple independent `Existence` instances and associated health-checks
+  endpoints (example use case: separate Kubernetes readiness and liveness http probes).
+* Checks states are stored and accessed using a dedicated ETS tables per `Existence` instance,
+  which means practically unlimited requests per second processing capacity.
 
 ## Installation
-Add library to application dependencies:
+Add `Existence` library to your application dependencies:
 ```elixir
 def deps do
   [
@@ -20,32 +22,26 @@ end
 ```
 
 ## Usage
-Start library child in your application supervisor:
+Define dependencies checks functions MFA's and start `Existence` child with your application
+supervisor
 ```elixir
 defmodule MyApp.Application do
   use Application
 
   def start(_type, _args) do
-    children = [Existence]
+    health_checks = [
+      check_1: %{mfa: {MyApp.Checks, :check_1, []}},
+      check_2: %{mfa: {MyApp.Checks, :check_2, []}}
+    ]
+
+    children = [{Existence, checks: health_checks}]
 
     opts = [strategy: :one_for_one, name: MyApp.Supervisor]
     Supervisor.start_link(children, opts)
   end
 end
 ```
 
-Configure dependencies checks in your application configuration file, for example:
-```elixir
-#config/config.exs
-config :my_app, Existence,
-  check_1: %{
-    mfa: {MyApp.Checks, :check_1, []}
-  },
-  check_2: %{
-    mfa: {MyApp.Checks, :check_2, []}
-  }
-```
-
 Declare your dependencies checks functions:
 ```elixir
 defmodule MyApp.Checks do
@@ -54,6 +50,16 @@ defmodule MyApp.Checks do
 end
 ```
 
+Configure your Phoenix router to respond to the `/healthcheck` endpoint requests using for example
+`Plug.Router.forward/2`:
+```elixir
+defmodule MyAppWeb.Router do
+  use MyAppWeb, :router
+
+  forward("/healthcheck", Existence.Plug)
+end
+```
+
 Get current overall health-check state:
 ```elixir
 iex> Existence.get_state()
@@ -66,16 +72,6 @@ iex> Existence.get_checks()
 [check_1: :ok, check_2: :ok]
 ```
 
-Configure your Phoenix router to respond to the `/healthcheck` endpoint requests using for example
-`Plug.Router.forward/2`:
-```elixir
-defmodule MyAppWeb.Router do
-  use MyAppWeb, :router
-
-  forward("/healthcheck", Existence.Plug)
-end
-```
-
 ## TODO
-- [ ] add `telemetry` event emitted on a health-check state change.
+- [ ] add `telemetry` event emitted on an overall health-check state change.