Add task for generating randomized device metrics (#1564)

lib/mix/tasks/fake.metrics.ex

@@ -0,0 +1,59 @@
+if Mix.env() == :dev do
+  defmodule Mix.Tasks.Fake.Metrics do
+    use Mix.Task
+
+    alias NervesHub.Repo
+    alias NervesHub.Devices
+    alias NervesHub.Devices.DeviceMetric
+
+    @shortdoc "Create randomized metrics for device"
+    @requirements ["app.start"]
+
+    @impl Mix.Task
+    def run([device_identifier | _]) do
+      {:ok, %{id: device_id}} = Devices.get_by_identifier(device_identifier)
+      now = DateTime.now!("Etc/UTC") |> DateTime.truncate(:millisecond)
+      a_week_ago = DateTime.add(now, -7, :day) |> DateTime.truncate(:millisecond)
+
+      add_metrics(device_id, now, a_week_ago)
+    end
+
+    @doc """
+    Runs recursively until current timestamp is less than or equal to ending timestamp
+    """
+    def add_metrics(device_id, current_timestamp, ending_timestamp)
+        when current_timestamp <= ending_timestamp,
+        do: save_metrics(device_id, current_timestamp)
+
+    def add_metrics(device_id, current_timestamp, ending_timestamp) do
+      save_metrics(device_id, current_timestamp)
+
+      new_timestamp = DateTime.add(current_timestamp, -20, :minute)
+      add_metrics(device_id, new_timestamp, ending_timestamp)
+    end
+
+    def save_metrics(device_id, current_timestamp) do
+      metrics = %{
+        "cpu_temp" => Enum.random(1..100),
+        "load_15min" => :rand.uniform() |> Float.ceil(2),
+        "load_1min" => :rand.uniform() |> Float.ceil(2),
+        "load_5min" => :rand.uniform() |> Float.ceil(2),
+        "size_mb" => 7892,
+        "used_mb" => Enum.random(0..7892),
+        "used_percent" => Enum.random(0..100)
+      }
+
+      Repo.transaction(fn ->
+        Enum.map(metrics, fn {key, val} ->
+          DeviceMetric.save_with_timestamp(%{
+            device_id: device_id,
+            key: key,
+            value: val,
+            inserted_at: current_timestamp
+          })
+          |> Repo.insert()
+        end)
+      end)
+    end
+  end
+end

lib/nerves_hub/devices/device_metric.ex

@@ -24,6 +24,16 @@ defmodule NervesHub.Devices.DeviceMetric do
     |> format_field(:key)
   end
 
+  @doc """
+  To use when creating fake metrics with manipulated timestamps
+  """
+  def save_with_timestamp(params) do
+    %__MODULE__{}
+    |> cast(params, @required_params ++ [:inserted_at])
+    |> validate_required(@required_params)
+    |> format_field(:key)
+  end
+
   defp format_field(%Changeset{changes: %{key: key}} = cs, :key) do
     # Just remove spaces for now.
     formatted_key = String.replace(key, " ", "")