Merge pull request #7 from jbsf2/remote-pid-fix

Fix crash when encountering remote pids

Author: jbsf2

.gitignore

@@ -27,4 +27,7 @@ process_tree-*.tar
 
 .vscode
 .tool-versions
-scratch.*
+scratch.*
+
+.idea
+*.iml

bin/dialyzer

@@ -2,12 +2,6 @@
 
 set -euxo pipefail
 
-asdf local erlang 24.3.4.14
-asdf local elixir 1.14.5-otp-24
-rm -rf _build
-mix local.hex --force
-mix dialyzer
-
 asdf local erlang 25.3.2.7
 asdf local elixir 1.14.5-otp-25
 rm -rf _build
@@ -20,12 +14,6 @@ rm -rf _build
 mix local.hex --force
 mix dialyzer
 
-asdf local erlang 24.3.4.14
-asdf local elixir 1.15.8-otp-24
-rm -rf _build
-mix local.hex --force
-mix dialyzer
-
 asdf local erlang 25.3.2.7
 asdf local elixir 1.15.8-otp-25
 rm -rf _build
@@ -38,12 +26,6 @@ rm -rf _build
 mix local.hex --force
 mix dialyzer
 
-asdf local erlang 24.3.4.14
-asdf local elixir 1.16.3-otp-24
-rm -rf _build
-mix local.hex --force
-mix dialyzer
-
 asdf local erlang 25.3.2.7
 asdf local elixir 1.16.3-otp-25
 rm -rf _build
@@ -68,26 +50,26 @@ rm -rf _build
 mix local.hex --force
 mix dialyzer
 
-asdf local erlang 27.2
+asdf local erlang 27.2.1
 asdf local elixir 1.17.3-otp-27
 rm -rf _build
 mix local.hex --force
 mix dialyzer
 
 asdf local erlang 25.3.2.7
-asdf local elixir 1.18.0-otp-25
+asdf local elixir 1.18.2-otp-25
 rm -rf _build
 mix local.hex --force
 mix dialyzer
 
 asdf local erlang 26.2.5.6
-asdf local elixir 1.18.0-otp-26
+asdf local elixir 1.18.2-otp-26
 rm -rf _build
 mix local.hex --force
 mix dialyzer
 
-asdf local erlang 27.2
-asdf local elixir 1.18.0-otp-27
+asdf local erlang 27.2.1
+asdf local elixir 1.18.2-otp-27
 rm -rf _build
 mix local.hex --force
 mix dialyzer

bin/script_builder.exs

@@ -2,25 +2,25 @@ defmodule ScriptBuilder do
 
   def elixir_builds() do
     [
-      {erlang_build("24"), "1.14.5-otp-24"},
+      # {erlang_build("24"), "1.14.5-otp-24"},
       {erlang_build("25"), "1.14.5-otp-25"},
       {erlang_build("26"), "1.14.5-otp-26"},
 
-      {erlang_build("24"), "1.15.8-otp-24"},
+      # {erlang_build("24"), "1.15.8-otp-24"},
       {erlang_build("25"), "1.15.8-otp-25"},
       {erlang_build("26"), "1.15.8-otp-26"},
 
-      {erlang_build("24"), "1.16.3-otp-24"},
+      # {erlang_build("24"), "1.16.3-otp-24"},
       {erlang_build("25"), "1.16.3-otp-25"},
       {erlang_build("26"), "1.16.3-otp-26"},
 
       {erlang_build("25"), "1.17.3-otp-25"},
       {erlang_build("26"), "1.17.3-otp-26"},
       {erlang_build("27"), "1.17.3-otp-27"},
 
-      {erlang_build("25"), "1.18.0-otp-25"},
-      {erlang_build("26"), "1.18.0-otp-26"},
-      {erlang_build("27"), "1.18.0-otp-27"},
+      {erlang_build("25"), "1.18.2-otp-25"},
+      {erlang_build("26"), "1.18.2-otp-26"},
+      {erlang_build("27"), "1.18.2-otp-27"},
     ]
   end
 
@@ -31,10 +31,10 @@ defmodule ScriptBuilder do
 
   def erlang_builds() do
     %{
-      "24" => "24.3.4.14",
+      # "24" => "24.3.4.14",
       "25" => "25.3.2.7",
       "26" => "26.2.5.6",
-      "27" => "27.2"
+      "27" => "27.2.1"
     }
   end
 
@@ -54,7 +54,7 @@ defmodule ScriptBuilder do
       IO.puts("asdf local erlang #{erlang_build}")
       IO.puts("asdf local elixir #{elixir_build}")
       IO.puts("mix local.hex --force")
-      IO.puts("mix test\n")
+      IO.puts("mix test --warnings-as-errors=false\n")
     end)
   end
 
@@ -72,4 +72,4 @@ defmodule ScriptBuilder do
   end
 end
 
-ScriptBuilder.test_commands()
+ScriptBuilder.dialyzer_commands()

bin/test

@@ -2,78 +2,63 @@
 
 set -euo pipefail
 
-asdf local erlang 24.3.4.14
-asdf local elixir 1.14.5-otp-24
-mix local.hex --force
-mix test
-
 asdf local erlang 25.3.2.7
 asdf local elixir 1.14.5-otp-25
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 26.2.5.6
 asdf local elixir 1.14.5-otp-26
 mix local.hex --force
-mix test
-
-asdf local erlang 24.3.4.14
-asdf local elixir 1.15.8-otp-24
-mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 25.3.2.7
 asdf local elixir 1.15.8-otp-25
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 26.2.5.6
 asdf local elixir 1.15.8-otp-26
 mix local.hex --force
-mix test
-
-asdf local erlang 24.3.4.14
-asdf local elixir 1.16.3-otp-24
-mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 25.3.2.7
 asdf local elixir 1.16.3-otp-25
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 26.2.5.6
 asdf local elixir 1.16.3-otp-26
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 25.3.2.7
 asdf local elixir 1.17.3-otp-25
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 26.2.5.6
 asdf local elixir 1.17.3-otp-26
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
-asdf local erlang 27.2
+asdf local erlang 27.2.1
 asdf local elixir 1.17.3-otp-27
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 25.3.2.7
-asdf local elixir 1.18.0-otp-25
+asdf local elixir 1.18.2-otp-25
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
 asdf local erlang 26.2.5.6
-asdf local elixir 1.18.0-otp-26
+asdf local elixir 1.18.2-otp-26
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 
-asdf local erlang 27.2
-asdf local elixir 1.18.0-otp-27
+asdf local erlang 27.2.1
+asdf local elixir 1.18.2-otp-27
 mix local.hex --force
-mix test
+mix test --warnings-as-errors=false
 

lib/process_tree.ex

@@ -18,6 +18,7 @@ defmodule ProcessTree do
     @dialyzer {:no_match, {:known_ancestors, 3}}
     @dialyzer {:no_match, {:try_parent, 4}}
     @dialyzer {:no_unused, {:older_dictionary_ancestors, 2}}
+    @dialyzer {:no_unused, {:ensure_pid_is_local, 1}}
   end
 
   @doc """
@@ -33,7 +34,7 @@ defmodule ProcessTree do
   subsequent calls to `get()` with the same key will return the cached value. This behavior
   can be disabled by passing `cache: false` as an option.
 
-  ## parents, `$ancestors` and `$callers`
+  ## Parents, `$ancestors` and `$callers`
 
   Erlang provides [two mechanisms](https://saltycrackers.dev/posts/how-to-get-the-parent-of-an-elixir-process/)
   for finding the ancestors of a process: `:erlang.process_info(pid, :parent)`, available
@@ -50,6 +51,12 @@ defmodule ProcessTree do
   if necessary examine the caller's parents/`$ancestors` and `$callers`, with priority again given to
   the parent/`$ancestors` hierarchy.
 
+  ## Remote ancestors
+
+  In cases where it is called within a process started by a remote node, for example via the
+  `Node.spawn` functions, `get()` will examine only the processes local to its node. Its
+  search stops when it encounters a remote pid.
+
   ## Options
 
   * `:cache` - If `false`, the value found in the tree will not be cached in the dictionaries
@@ -107,6 +114,11 @@ defmodule ProcessTree do
   is spawned by parent/grandparent GenServers that have registered names, and the parent GenServer dies,
   then the parent & grandparent may be represented in the list of the child's known ancestors using
   the their registered names - atoms, rather than pids. Precise behavior depends on OTP major version.
+
+  In cases where it is called within a process started by a remote node, for example via the
+  `Node.spawn` functions, the list returned by `known_ancestors()` will contain only the pids
+  belonging to the local node. `known_ancestors()` ends its search when it encounters a remote
+  pid in the ancestry hierarchy.
   """
   @spec known_ancestors(pid()) :: [pid() | atom()]
   def known_ancestors(pid) do
@@ -117,7 +129,7 @@ defmodule ProcessTree do
   @doc """
   Returns the parent of `pid`, if the parent is known.
 
-  Returns `:unknown` if the parent is unknown.
+  Returns `:unknown` if the parent is unknown, or if the parent belongs to a remote node.
 
   Returns `:undefined` if `pid` represents the `:init` process (`PID<0.0.0>`).
 
@@ -254,7 +266,7 @@ defmodule ProcessTree do
           nil
 
         {:parent, parent} ->
-          parent
+          ensure_pid_is_local(parent)
 
         nil ->
           nil
@@ -268,6 +280,14 @@ defmodule ProcessTree do
     defp process_info_parent(_pid), do: nil
   end
 
+  @spec ensure_pid_is_local(pid()) :: pid() | nil
+  defp ensure_pid_is_local(pid) do
+    case node(pid) == node() do
+      true -> pid
+      false -> nil
+    end
+  end
+
   @spec get_dictionary_value(id(), term()) :: term()
   defp get_dictionary_value(nil, _key), do: nil
 

mix.exs

@@ -1,7 +1,7 @@
 defmodule ProcessTree.MixProject do
   use Mix.Project
 
-  @version "0.2.0"
+  @version "0.2.1"
   @github_page "https://github.com/jbsf2/process-tree"
 
   def project do

mix.lock

@@ -1,10 +1,10 @@
 %{
-  "dialyxir": {:hex, :dialyxir, "1.4.3", "edd0124f358f0b9e95bfe53a9fcf806d615d8f838e2202a9f430d59566b6b53b", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "bf2cfb75cd5c5006bec30141b131663299c661a864ec7fbbc72dfa557487a986"},
-  "earmark_parser": {:hex, :earmark_parser, "1.4.39", "424642f8335b05bb9eb611aa1564c148a8ee35c9c8a8bba6e129d51a3e3c6769", [:mix], [], "hexpm", "06553a88d1f1846da9ef066b87b57c6f605552cfbe40d20bd8d59cc6bde41944"},
-  "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
+  "dialyxir": {:hex, :dialyxir, "1.4.5", "ca1571ac18e0f88d4ab245f0b60fa31ff1b12cbae2b11bd25d207f865e8ae78a", [:mix], [{:erlex, ">= 0.2.7", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "b0fb08bb8107c750db5c0b324fa2df5ceaa0f9307690ee3c1f6ba5b9eb5d35c3"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.43", "34b2f401fe473080e39ff2b90feb8ddfeef7639f8ee0bbf71bb41911831d77c5", [:mix], [], "hexpm", "970a3cd19503f5e8e527a190662be2cee5d98eed1ff72ed9b3d1a3d466692de8"},
+  "erlex": {:hex, :erlex, "0.2.7", "810e8725f96ab74d17aac676e748627a07bc87eb950d2b83acd29dc047a30595", [:mix], [], "hexpm", "3ed95f79d1a844c3f6bf0cea61e0d5612a42ce56da9c03f01df538685365efb0"},
   "ex_doc": {:hex, :ex_doc, "0.30.9", "d691453495c47434c0f2052b08dd91cc32bc4e1a218f86884563448ee2502dd2", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "d7aaaf21e95dc5cddabf89063327e96867d00013963eadf2c6ad135506a8bc10"},
-  "makeup": {:hex, :makeup, "1.1.1", "fa0bc768698053b2b3869fa8a62616501ff9d11a562f3ce39580d60860c3a55e", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "5dc62fbdd0de44de194898b6710692490be74baa02d9d108bc29f007783b0b48"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
-  "makeup_erlang": {:hex, :makeup_erlang, "0.1.3", "d684f4bac8690e70b06eb52dad65d26de2eefa44cd19d64a8095e1417df7c8fd", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "b78dc853d2e670ff6390b605d807263bf606da3c82be37f9d7f68635bd886fc9"},
-  "nimble_parsec": {:hex, :nimble_parsec, "1.4.0", "51f9b613ea62cfa97b25ccc2c1b4216e81df970acd8e16e8d1bdc58fef21370d", [:mix], [], "hexpm", "9c565862810fb383e9838c1dd2d7d2c437b3d13b267414ba6af33e50d2d1cf28"},
+  "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
+  "makeup_elixir": {:hex, :makeup_elixir, "0.16.2", "627e84b8e8bf22e60a2579dad15067c755531fea049ae26ef1020cad58fe9578", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "41193978704763f6bbe6cc2758b84909e62984c7752b3784bd3c218bb341706b"},
+  "makeup_erlang": {:hex, :makeup_erlang, "0.1.5", "e0ff5a7c708dda34311f7522a8758e23bfcd7d8d8068dc312b5eb41c6fd76eba", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "94d2e986428585a21516d7d7149781480013c56e30c6a233534bedf38867a59a"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.4.2", "8efba0122db06df95bfaa78f791344a89352ba04baedd3849593bfce4d0dc1c6", [:mix], [], "hexpm", "4b21398942dda052b403bbe1da991ccd03a053668d147d53fb8c4e0efe09c973"},
 }

test/process_tree_test.exs

@@ -442,6 +442,57 @@ defmodule ProcessTreeTest do
     end
   end
 
+  describe "handling remote pids" do
+    setup do
+      ensure_epmd_running()
+      ensure_local_node_started()
+      :ok
+    end
+
+    test "get() stops walking the tree if it encounters a remote pid" do
+      Node.spawn_link(remote_node(), RemoteTestFunctions, :test_nested_get, [self()])
+
+      assert_receive :done
+    end
+
+    test "known_ancestors() only includes ancestors on the local node" do
+      Node.spawn_link(remote_node(), RemoteTestFunctions, :test_ancestors, [self()])
+
+      assert_receive :done
+    end
+
+    test "parent() doesn't blow up"  do
+      Node.spawn_link(remote_node(), RemoteTestFunctions, :test_get_parent, [self()])
+
+      assert_receive :done
+    end
+  end
+
+  @spec remote_node() :: node()
+  defp remote_node() do
+    {:ok, pid, _} =
+      :peer.start_link(%{connection: :standard_io, args: [~c"-pa" | :code.get_path()]})
+
+    :peer.call(pid, :net_kernel, :start, [[:other, :shortnames]])
+    :peer.call(pid, :erlang, :node, [])
+  end
+
+  defp ensure_local_node_started() do
+    %{started: started} = :net_kernel.get_state()
+
+    if started == :no do
+      {:ok, _} = :net_kernel.start([:process_tree_test, :shortnames])
+    end
+  end
+
+  defp ensure_epmd_running() do
+    {_, exit_code} = System.cmd("epmd", ["-names"], stderr_to_stdout: true)
+
+    if exit_code != 0 do
+      System.cmd("epmd", ["-daemon"])
+    end
+  end
+
   @spec full_name(atom()) :: atom()
   defp full_name(pid_name) do
     prefix = Process.get(:process_name_prefix)