Merge pull request #286 from dylantirandaz/enhance-telemetry-and-distribution

Enhance telemetry and distribution strategy typespecs

Author: sleipnir

lib/horde/dynamic_supervisor_impl.ex

@@ -104,9 +104,13 @@ defmodule Horde.DynamicSupervisorImpl do
   end
 
   def handle_call(:get_telemetry, _from, state) do
+    members_info = Map.values(state.members_info)
+
     telemetry = %{
       global_supervised_process_count: size_of(state.processes_by_id),
-      local_supervised_process_count: state.local_process_count
+      local_supervised_process_count: state.local_process_count,
+      alive_members_count: Enum.count(members_info, &match?(%{status: :alive}, &1)),
+      total_members_count: length(members_info)
     }
 
     {:reply, telemetry, state}

lib/horde/uniform_distribution.ex

@@ -8,6 +8,9 @@ defmodule Horde.UniformDistribution do
   the same process on the same node.
   """
 
+  @impl true
+  @spec choose_node(Supervisor.child_spec(), [Horde.DistributionStrategy.member()]) ::
+          {:ok, Horde.DistributionStrategy.member()} | {:error, :no_alive_nodes}
   def choose_node(child_spec, members) do
     identifier = :erlang.phash2(Map.drop(child_spec, [:id]))
 
@@ -28,5 +31,7 @@ defmodule Horde.UniformDistribution do
     end
   end
 
+  @impl true
+  @spec has_quorum?([Horde.DistributionStrategy.member()]) :: boolean()
   def has_quorum?(_members), do: true
 end

lib/horde/uniform_quorum_distribution.ex

@@ -8,6 +8,9 @@ defmodule Horde.UniformQuorumDistribution do
   """
   require Integer
 
+  @impl true
+  @spec choose_node(Supervisor.child_spec(), [Horde.DistributionStrategy.member()]) ::
+          {:ok, Horde.DistributionStrategy.member()} | {:error, :no_alive_nodes | :quorum_not_met}
   def choose_node(child_spec, members) do
     if has_quorum?(members) do
       Horde.UniformDistribution.choose_node(child_spec, members)
@@ -16,6 +19,8 @@ defmodule Horde.UniformQuorumDistribution do
     end
   end
 
+  @impl true
+  @spec has_quorum?([Horde.DistributionStrategy.member()]) :: boolean() | nil
   def has_quorum?([]), do: false
 
   def has_quorum?(members) do

lib/horde/uniform_random_distribution.ex

@@ -9,6 +9,9 @@ defmodule Horde.UniformRandomDistribution do
   @doc """
   Selects a random alive node.
   """
+  @impl true
+  @spec choose_node(Supervisor.child_spec(), [Horde.DistributionStrategy.member()]) ::
+          {:ok, Horde.DistributionStrategy.member()} | {:error, :no_alive_nodes}
   def choose_node(_identifier, members) do
     members
     |> Enum.filter(&match?(%{status: :alive}, &1))
@@ -29,5 +32,7 @@ defmodule Horde.UniformRandomDistribution do
   Quorum checks are not enforced, so the process will be
   (re)started on  both sides of a netsplit.
   """
+  @impl true
+  @spec has_quorum?([Horde.DistributionStrategy.member()]) :: boolean()
   def has_quorum?(_members), do: true
 end

test/supervisor_telemetry_poller_test.exs

@@ -13,7 +13,15 @@ defmodule SupervisorTelemetryPollerTest do
 
     def init(_), do: {:ok, %{}}
 
-    def handle_call(:get_telemetry, _, state), do: {:reply, %{metrics: 1}, state}
+    def handle_call(:get_telemetry, _, state) do
+      {:reply,
+       %{
+         global_supervised_process_count: 2,
+         local_supervised_process_count: 1,
+         alive_members_count: 3,
+         total_members_count: 3
+       }, state}
+    end
   end
 
   setup do

test/uniform_distribution_test.exs

@@ -32,6 +32,25 @@ defmodule UniformDistributionTest do
     end
   end
 
+  property "is deterministic for the same input" do
+    check all(
+            identifier <- string(:alphanumeric, min_length: 1),
+            member_count <- integer(1..10)
+          ) do
+      members =
+        Enum.map(1..member_count, fn i ->
+          %{node_id: i, status: :alive, name: :"node_#{i}", pid: :pid}
+        end)
+
+      child_spec = %{id: identifier, start: {identifier}}
+
+      result1 = Horde.UniformDistribution.choose_node(child_spec, members)
+      result2 = Horde.UniformDistribution.choose_node(child_spec, members)
+
+      assert result1 == result2
+    end
+  end
+
   property "returns error if no alive nodes are available" do
     member =
       ExUnitProperties.gen all(