test: cover pure cores (units, budget data, cgroup/nss parsers) (#22)

Author: markovejnovic

lib/sys/linux/cgroup.ex

@@ -12,16 +12,19 @@ defmodule Sys.Linux.Cgroup do
   @spec versions :: {:ok, MapSet.t(:cgroup | :cgroup2)} | {:error, atom()}
   def versions do
     case Mounts.list() do
-      {:ok, mounts} ->
-        versions =
-          for %{fs_type: fs} <- mounts, fs in ~w(cgroup cgroup2), into: MapSet.new() do
-            String.to_existing_atom(fs)
-          end
-
-        {:ok, versions}
+      {:ok, mounts} -> {:ok, versions_from_mounts(mounts)}
+      {:error, reason} -> {:error, reason}
+    end
+  end
 
-      {:error, reason} ->
-        {:error, reason}
+  @doc """
+  Reduce a list of mounts to the set of cgroup versions present, keyed by
+  filesystem type. Pure; `versions/0` is this applied to `/proc/mounts`.
+  """
+  @spec versions_from_mounts([Sys.Linux.Fstab.Spec.t()]) :: MapSet.t(:cgroup | :cgroup2)
+  def versions_from_mounts(mounts) do
+    for %{fs_type: fs} <- mounts, fs in ~w(cgroup cgroup2), into: MapSet.new() do
+      String.to_existing_atom(fs)
     end
   end
 end

lib/sys/linux/nss.ex

@@ -27,17 +27,23 @@ defmodule Sys.Linux.Nss do
                {:getent_failed, non_neg_integer()} | :getent_unavailable | :invalid_format}
     def entries do
       with {:ok, output} <- Sys.Linux.Nss.getent(@getent_db) do
-        output
-        |> String.split("\n", trim: true)
-        |> Enum.reduce_while({:ok, []}, fn line, {:ok, acc} ->
-          case parse(line) do
-            {:ok, spec} -> {:cont, {:ok, [spec | acc]}}
-            {:error, _} = error -> {:halt, error}
-          end
-        end)
+        from_output(output)
       end
     end
 
+    @doc "Parse raw `getent passwd` output into specs, halting on the first bad line."
+    @spec from_output(binary()) :: {:ok, [Spec.t()]} | {:error, :invalid_format}
+    def from_output(output) do
+      output
+      |> String.split("\n", trim: true)
+      |> Enum.reduce_while({:ok, []}, fn line, {:ok, acc} ->
+        case parse(line) do
+          {:ok, spec} -> {:cont, {:ok, [spec | acc]}}
+          {:error, _} = error -> {:halt, error}
+        end
+      end)
+    end
+
     # passwd line: name:password:uid:gid:gecos:home_dir:shell
     @spec parse(String.t()) :: {:ok, Spec.t()} | {:error, :invalid_format}
     defp parse(line) do
@@ -83,17 +89,23 @@ defmodule Sys.Linux.Nss do
                {:getent_failed, non_neg_integer()} | :getent_unavailable | :invalid_format}
     def entries do
       with {:ok, output} <- Sys.Linux.Nss.getent(@getent_db) do
-        output
-        |> String.split("\n", trim: true)
-        |> Enum.reduce_while({:ok, []}, fn line, {:ok, acc} ->
-          case parse(line) do
-            {:ok, spec} -> {:cont, {:ok, [spec | acc]}}
-            {:error, _} = error -> {:halt, error}
-          end
-        end)
+        from_output(output)
       end
     end
 
+    @doc "Parse raw `getent group` output into specs, halting on the first bad line."
+    @spec from_output(binary()) :: {:ok, [Spec.t()]} | {:error, :invalid_format}
+    def from_output(output) do
+      output
+      |> String.split("\n", trim: true)
+      |> Enum.reduce_while({:ok, []}, fn line, {:ok, acc} ->
+        case parse(line) do
+          {:ok, spec} -> {:cont, {:ok, [spec | acc]}}
+          {:error, _} = error -> {:halt, error}
+        end
+      end)
+    end
+
     # group line: name:password:gid:member1,member2,...
     @spec parse(String.t()) :: {:ok, Spec.t()} | {:error, :invalid_format}
     defp parse(line) do

test/hyper/node/budget/hard_state_properties_test.exs

@@ -0,0 +1,67 @@
+defmodule Hyper.Node.Budget.HardStatePropertiesTest do
+  @moduledoc """
+  Algebraic laws of the pure `Hyper.Node.Budget.Hard.State` accumulator: `cut`
+  is the inverse of `bump` on every spec, bumps accumulate additively (so the
+  running total is order-independent), and `track`/`untrack` round-trip a
+  reservation by reference. The example tests spot-check single values; these
+  pin the laws across the domain.
+  """
+  use ExUnit.Case, async: true
+  use ExUnitProperties
+
+  alias Hyper.Node.Budget.Hard.State
+  alias Hyper.Vm.Instance.Spec
+  alias Unit.{Bandwidth, Information}
+
+  # Only `mem`/`disk` matter to bump/cut; the other fields are along for the ride.
+  defp spec do
+    gen all(mem_mib <- integer(0..1_000_000), disk_mib <- integer(0..1_000_000)) do
+      %Spec{
+        vcpus: 1,
+        mem: Information.mib(mem_mib),
+        disk: Information.mib(disk_mib),
+        disk_bw: Bandwidth.zero(),
+        net_bw: Bandwidth.zero()
+      }
+    end
+  end
+
+  property "cut undoes bump for any spec" do
+    check all(s <- spec()) do
+      state = State.zero() |> State.bump(s) |> State.cut(s)
+      assert state.mem_allocated == Information.zero()
+      assert state.disk_allocated == Information.zero()
+    end
+  end
+
+  property "the running total is the sum of bumped specs (hence order-independent)" do
+    check all(specs <- list_of(spec(), max_length: 20)) do
+      state = Enum.reduce(specs, State.zero(), fn s, acc -> State.bump(acc, s) end)
+
+      total_mem = specs |> Enum.map(&Information.as_bytes(&1.mem)) |> Enum.sum()
+      total_disk = specs |> Enum.map(&Information.as_bytes(&1.disk)) |> Enum.sum()
+
+      assert Information.as_bytes(state.mem_allocated) == total_mem
+      assert Information.as_bytes(state.disk_allocated) == total_disk
+    end
+  end
+
+  property "untrack returns exactly the spec track stored, leaving the rest unchanged" do
+    check all(s <- spec()) do
+      base = State.zero()
+      ref = make_ref()
+      tracked = State.track(base, ref, s)
+      assert {^s, rest} = State.untrack(tracked, ref)
+      assert rest.reservations == base.reservations
+    end
+  end
+
+  property "untrack of a ref that was never tracked yields nil and an unchanged state" do
+    check all(s <- spec()) do
+      ref = make_ref()
+      other = make_ref()
+      state = State.track(State.zero(), ref, s)
+      assert {nil, ^state} = State.untrack(state, other)
+    end
+  end
+end

test/hyper/node/budget/node_state_properties_test.exs

@@ -0,0 +1,89 @@
+defmodule Hyper.Node.Budget.NodeStatePropertiesTest do
+  @moduledoc """
+  Monotonicity laws of the pure `NodeState.fits?/2` predicate, complementing the
+  exact-`<=`-boundary example tests. A spec strictly within every ceiling always
+  fits, exceeding free memory always fails, and a spec that fits a node still
+  fits a node with strictly more headroom.
+  """
+  use ExUnit.Case, async: true
+  use ExUnitProperties
+  use Unit.Operators
+
+  alias Hyper.Node.Budget.NodeState
+  alias Hyper.Vm.Instance.Spec
+  alias Unit.{Bandwidth, Information}
+
+  # A node, idle on every soft metric with `cpu_max_load` at 1.0, so the only
+  # binding limits are the generated hard headrooms and cpu capacity.
+  defp state do
+    gen all(
+          mem_gib <- integer(1..64),
+          disk_gib <- integer(1..1000),
+          cpu_cap <- integer(1..128)
+        ) do
+      %NodeState{
+        node: :n@h,
+        mem_free: Information.gib(mem_gib),
+        disk_free: Information.gib(disk_gib),
+        cpu_load: 0.0,
+        cpu_capacity: cpu_cap,
+        cpu_max_load: 1.0,
+        disk_bw_load: Bandwidth.zero(),
+        disk_bw_ceiling: Bandwidth.gibps(10),
+        net_bw_load: Bandwidth.zero(),
+        net_bw_ceiling: Bandwidth.gibps(10),
+        layers: []
+      }
+    end
+  end
+
+  # A spec whose demand sits within every ceiling of `st`.
+  defp fitting_spec(st) do
+    gen all(
+          mem_gib <- integer(0..Information.as_gib(st.mem_free)),
+          disk_gib <- integer(0..Information.as_gib(st.disk_free)),
+          vcpus <- integer(0..st.cpu_capacity)
+        ) do
+      %Spec{
+        vcpus: vcpus,
+        mem: Information.gib(mem_gib),
+        disk: Information.gib(disk_gib),
+        disk_bw: Bandwidth.zero(),
+        net_bw: Bandwidth.zero()
+      }
+    end
+  end
+
+  property "a spec within every ceiling always fits" do
+    check all(st <- state(), spec <- fitting_spec(st)) do
+      assert NodeState.fits?(st, spec)
+    end
+  end
+
+  property "exceeding free memory always fails" do
+    check all(st <- state(), over <- integer(1..1000)) do
+      spec = %Spec{
+        vcpus: 0,
+        mem: st.mem_free + Information.gib(over),
+        disk: Information.zero(),
+        disk_bw: Bandwidth.zero(),
+        net_bw: Bandwidth.zero()
+      }
+
+      refute NodeState.fits?(st, spec)
+    end
+  end
+
+  property "a fitting spec still fits when the node gains headroom" do
+    check all(st <- state(), spec <- fitting_spec(st), extra <- integer(0..100)) do
+      roomier = %{
+        st
+        | mem_free: st.mem_free + Information.gib(extra),
+          disk_free: st.disk_free + Information.gib(extra)
+      }
+
+      # Precondition the law on the spec actually fitting `st`.
+      if NodeState.fits?(st, spec), do: assert(NodeState.fits?(roomier, spec))
+    end
+  end
+end

test/hyper/node/budget/node_state_test.exs

@@ -0,0 +1,81 @@
+defmodule Hyper.Node.Budget.NodeStateTest do
+  use ExUnit.Case, async: true
+
+  alias Hyper.Node.Budget.NodeState
+  alias Hyper.Vm.Instance.Spec
+  alias Unit.{Bandwidth, Information}
+
+  # A node with generous headroom, idle on every metric. Override per case.
+  defp roomy_state(overrides \\ %{}) do
+    struct!(
+      %NodeState{
+        node: :node@host,
+        mem_free: Information.gib(8),
+        disk_free: Information.gib(100),
+        cpu_load: 0.0,
+        cpu_capacity: 8,
+        cpu_max_load: 0.8,
+        disk_bw_load: Bandwidth.zero(),
+        disk_bw_ceiling: Bandwidth.gibps(1),
+        net_bw_load: Bandwidth.zero(),
+        net_bw_ceiling: Bandwidth.gibps(1),
+        layers: []
+      },
+      overrides
+    )
+  end
+
+  defp spec(overrides \\ %{}) do
+    struct!(
+      %Spec{
+        vcpus: 1,
+        mem: Information.gib(1),
+        disk: Information.gib(10),
+        disk_bw: Bandwidth.mibps(10),
+        net_bw: Bandwidth.mibps(10)
+      },
+      overrides
+    )
+  end
+
+  test "a spec that fits every metric is admitted" do
+    assert NodeState.fits?(roomy_state(), spec())
+  end
+
+  test "memory demand over free headroom is rejected" do
+    state = roomy_state(%{mem_free: Information.gib(1)})
+    refute NodeState.fits?(state, spec(%{mem: Information.gib(2)}))
+  end
+
+  test "memory demand exactly at free headroom still fits (<= boundary)" do
+    state = roomy_state(%{mem_free: Information.gib(2)})
+    assert NodeState.fits?(state, spec(%{mem: Information.gib(2)}))
+  end
+
+  test "disk demand over free headroom is rejected" do
+    state = roomy_state(%{disk_free: Information.gib(5)})
+    refute NodeState.fits?(state, spec(%{disk: Information.gib(6)}))
+  end
+
+  test "cpu demand that crosses the load ceiling is rejected" do
+    # load 0.5 + 3 vcpus / 8 cores = 0.875 > cpu_max_load 0.8
+    state = roomy_state(%{cpu_load: 0.5})
+    refute NodeState.fits?(state, spec(%{vcpus: 3}))
+  end
+
+  test "cpu demand exactly at the load ceiling still fits" do
+    # load 0.0 + 8 vcpus / 8 cores = 1.0 <= cpu_max_load 1.0
+    state = roomy_state(%{cpu_max_load: 1.0})
+    assert NodeState.fits?(state, spec(%{vcpus: 8}))
+  end
+
+  test "disk bandwidth over its ceiling is rejected" do
+    state = roomy_state(%{disk_bw_ceiling: Bandwidth.mibps(5)})
+    refute NodeState.fits?(state, spec(%{disk_bw: Bandwidth.mibps(6)}))
+  end
+
+  test "net bandwidth over its ceiling is rejected" do
+    state = roomy_state(%{net_bw_ceiling: Bandwidth.mibps(5)})
+    refute NodeState.fits?(state, spec(%{net_bw: Bandwidth.mibps(6)}))
+  end
+end

test/sys/linux/cgroup_properties_test.exs

@@ -0,0 +1,64 @@
+defmodule Sys.Linux.CgroupPropertiesTest do
+  @moduledoc """
+  `Cgroup.versions_from_mounts/1` reduces a mount list to the set of cgroup
+  versions present, keyed by `fs_type`. The result is exactly the cgroup
+  fs_types that appear: it ignores every other filesystem, is insensitive to
+  order and duplication, and never contains a version that was not mounted.
+  """
+  use ExUnit.Case, async: true
+  use ExUnitProperties
+
+  alias Sys.Linux.Cgroup
+  alias Sys.Linux.Fstab.Spec
+
+  @cgroup_fs ~w(cgroup cgroup2)
+  # Filesystem types that must never contribute to the result.
+  @other_fs ~w(ext4 xfs btrfs proc sysfs tmpfs overlay)
+
+  defp mount(fs_type) do
+    %Spec{device: "none", mount_point: "/x", fs_type: fs_type, mount_opts: "rw"}
+  end
+
+  defp fs_type, do: member_of(@cgroup_fs ++ @other_fs)
+
+  property "the result is exactly the set of cgroup fs_types present" do
+    check all(types <- list_of(fs_type(), max_length: 20)) do
+      mounts = Enum.map(types, &mount/1)
+
+      expected =
+        types
+        |> Enum.filter(&(&1 in @cgroup_fs))
+        |> Enum.map(&String.to_existing_atom/1)
+        |> MapSet.new()
+
+      assert Cgroup.versions_from_mounts(mounts) == expected
+    end
+  end
+
+  property "non-cgroup mounts never change the result" do
+    check all(
+            types <- list_of(member_of(@cgroup_fs), max_length: 10),
+            noise <- list_of(member_of(@other_fs), max_length: 10)
+          ) do
+      base = Enum.map(types, &mount/1)
+      with_noise = Enum.map(types ++ noise, &mount/1)
+      assert Cgroup.versions_from_mounts(base) == Cgroup.versions_from_mounts(with_noise)
+    end
+  end
+
+  property "order and duplication do not affect the result" do
+    check all(types <- list_of(fs_type(), max_length: 20)) do
+      mounts = Enum.map(types, &mount/1)
+      result = Cgroup.versions_from_mounts(mounts)
+      assert Cgroup.versions_from_mounts(Enum.reverse(mounts)) == result
+      assert Cgroup.versions_from_mounts(mounts ++ mounts) == result
+    end
+  end
+
+  property "the result is always a subset of {:cgroup, :cgroup2}" do
+    check all(types <- list_of(fs_type(), max_length: 20)) do
+      result = Cgroup.versions_from_mounts(Enum.map(types, &mount/1))
+      assert MapSet.subset?(result, MapSet.new([:cgroup, :cgroup2]))
+    end
+  end
+end