initial commit

right now, all that happens is the genserver pulls configs at startup,
stores them in ETS, and reloads them every 60s

Author: peburrows

.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

@@ -0,0 +1,24 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+statsig_ex-*.tar
+

README.md

@@ -0,0 +1,6 @@
+# StatsigEx
+
+**This is very much a work in progress**
+
+I want to see how quickly we can replicate the funcationality in 
+Statsig's erlang client and fix some of the issues they claim it has

config/config.exs

@@ -0,0 +1,30 @@
+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# third-party users, it should be done in your "mix.exs" file.
+
+# You can configure your application as:
+#
+#     config :statsig_ex, key: :value
+#
+# and access this configuration in your application as:
+#
+#     Application.get_env(:statsig_ex, :key)
+#
+# You can also configure a third-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env()}.exs"

lib/statsig_ex.ex

@@ -0,0 +1,98 @@
+defmodule StatsigEx do
+  use GenServer
+
+  def start_link(opts \\ []) do
+    # should pull from an env var here
+    opts = Keyword.put_new(opts, :api_key, {:env, "STATSIG_API_KEY"})
+
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  def init(opts) do
+    :ets.new(ets_name(), [:named_table])
+
+    state = %{
+      api_key: get_api_key(Keyword.fetch!(opts, :api_key)),
+      last_sync: 0,
+      events: []
+    }
+
+    {:ok, last_sync} = reload_configs(state.api_key, state.last_sync)
+
+    # reload every 60s
+    Process.send_after(self(), :reload, 60_000)
+    {:ok, Map.put(state, :last_sync, last_sync)}
+  end
+
+  def state, do: GenServer.call(__MODULE__, :state)
+
+  def ets_name, do: :statsig_ex_store
+
+  # for debugging
+  def handle_call(:state, _from, state) do
+    {:reply, state, state}
+  end
+
+  def handle_call({:log, event}, _from, state) do
+    # for now, just throw things in there, don't worry about the shape
+    {:reply, :ok, Map.put(state, :events, [event | state.events])}
+  end
+
+  def handle_info(:reload, %{api_key: key, last_sync: time} = state) do
+    {:ok, sync_time} = reload_configs(key, time)
+    IO.puts("reloading!")
+    Process.send_after(self(), :reload, 60_000)
+    {:noreply, Map.put(state, :last_sync, sync_time)}
+  end
+
+  def handle_info(:flush, %{api_key: key, events: events} = state) do
+    remaining = flush_events(key, events)
+    {:noreply, Map.put(state, :events, remaining)}
+  end
+
+  defp reload_configs(api_key, since) do
+    # call Statsig API to get configs (eventually we can make the http client configurable)
+    {:ok, resp} =
+      HTTPoison.get(
+        "https://statsigapi.net/v1/download_config_specs?sinceTime=#{since}",
+        [{"STATSIG-API-KEY", api_key}, {"Content-Type", "application/json"}]
+      )
+
+    # should probably crash on startup but be resilient on reload; will fix later
+    config = Jason.decode!(resp.body)
+    config |> Map.get("feature_gates", []) |> save_configs(:gate)
+    config |> Map.get("dynamic_configs", []) |> save_configs(:config)
+
+    # return the time of this last fetch
+    {:ok, Map.get(config, "time", since)}
+  end
+
+  def flush_events(_key, []), do: []
+
+  def flush_events(key, events) do
+    # send in batches; keep any that fail
+    events
+    |> Enum.chunk_every(500)
+    |> Enum.reduce([], fn chunk, unsent ->
+      # this probably doesn't work yet, but I'm not really worried about it right now
+      {:ok, _resp} =
+        HTTPoison.post(
+          "https://statsigapi.net/v1/rgstr",
+          Jason.encode!(%{"events" => chunk}),
+          [{"STATSIG-API-KEY", key}, {"Content-Type", "application/json"}]
+        )
+    end)
+  end
+
+  defp get_api_key({:env, var}), do: System.get_env(var)
+  defp get_api_key(key), do: key
+
+  defp save_configs([], _), do: :ok
+
+  defp save_configs([%{"name" => name} = head | tail], type) when is_binary(name) do
+    :ets.insert(ets_name(), {{name, type}, head})
+    save_configs(tail, type)
+  end
+
+  defp save_configs([_head | tail], type), do: save_configs(tail, type)
+end

lib/statsig_ex/api_client.ex

@@ -0,0 +1,3 @@
+defmodule StatsigEx.APIClient do
+  # we'll refactor to use this later
+end

mix.exs

@@ -0,0 +1,29 @@
+defmodule StatsigEx.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :statsig_ex,
+      version: "0.1.0",
+      elixir: "~> 1.8",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      applications: [:httpoison]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:httpoison, "~> 1.4"},
+      {:jason, "~> 1.2"}
+    ]
+  end
+end

mix.lock

@@ -0,0 +1,12 @@
+%{
+  "certifi": {:hex, :certifi, "2.12.0", "2d1cca2ec95f59643862af91f001478c9863c2ac9cb6e2f89780bfd8de987329", [:rebar3], [], "hexpm", "ee68d85df22e554040cdb4be100f33873ac6051387baf6a8f6ce82272340ff1c"},
+  "hackney": {:hex, :hackney, "1.20.1", "8d97aec62ddddd757d128bfd1df6c5861093419f8f7a4223823537bad5d064e2", [:rebar3], [{:certifi, "~>2.12.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~>6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~>1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.4.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~>1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "fe9094e5f1a2a2c0a7d10918fee36bfec0ec2a979994cff8cfe8058cd9af38e3"},
+  "httpoison": {:hex, :httpoison, "1.8.2", "9eb9c63ae289296a544842ef816a85d881d4a31f518a0fec089aaa744beae290", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "2bb350d26972e30c96e2ca74a1aaf8293d61d0742ff17f01e0279fef11599921"},
+  "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
+  "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
+  "mimerl": {:hex, :mimerl, "1.3.0", "d0cd9fc04b9061f82490f6581e0128379830e78535e017f7780f37fea7545726", [:rebar3], [], "hexpm", "a1e15a50d1887217de95f0b9b0793e32853f7c258a5cd227650889b38839fe9d"},
+  "parse_trans": {:hex, :parse_trans, "3.4.1", "6e6aa8167cb44cc8f39441d05193be6e6f4e7c2946cb2759f015f8c56b76e5ff", [:rebar3], [], "hexpm", "620a406ce75dada827b82e453c19cf06776be266f5a67cff34e1ef2cbb60e49a"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.7", "354c321cf377240c7b8716899e182ce4890c5938111a1296add3ec74cf1715df", [:make, :mix, :rebar3], [], "hexpm", "fe4c190e8f37401d30167c8c405eda19469f34577987c76dde613e838bbc67f8"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.0", "bc84380c9ab48177092f43ac89e4dfa2c6d62b40b8bd132b1059ecc7232f9a78", [:rebar3], [], "hexpm", "25eee6d67df61960cf6a794239566599b09e17e668d3700247bc498638152521"},
+}

test/statsig_ex_test.exs

@@ -0,0 +1,8 @@
+defmodule StatsigExTest do
+  use ExUnit.Case
+  doctest StatsigEx
+
+  test "greets the world" do
+    assert StatsigEx.hello() == :world
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()