feat: add sync relay guard fanout gating and env config

.env.example

@@ -13,6 +13,7 @@ POOL_SIZE=20
 # PARRHESIA_POLICIES_AUTH_REQUIRED_FOR_WRITES=false
 # PARRHESIA_POLICIES_AUTH_REQUIRED_FOR_READS=false
 # PARRHESIA_POLICIES_MIN_POW_DIFFICULTY=0
+# PARRHESIA_SYNC_RELAY_GUARD=false
 # PARRHESIA_FEATURES_VERIFY_EVENT_SIGNATURES=true
 # PARRHESIA_METRICS_ENABLED_ON_MAIN_ENDPOINT=true
 # PARRHESIA_METRICS_PRIVATE_NETWORKS_ONLY=true

README.md

@@ -262,6 +262,7 @@ CSV env vars use comma-separated values. Boolean env vars accept `1/0`, `true/fa
 | `:nip66` | config-file driven | see table below | Built-in NIP-66 discovery / monitor publisher |
 | `:sync.path` | `PARRHESIA_SYNC_PATH` | `nil` | Optional path to sync peer config |
 | `:sync.start_workers?` | `PARRHESIA_SYNC_START_WORKERS` | `true` | Start outbound sync workers on boot |
+| `:sync.relay_guard` | `PARRHESIA_SYNC_RELAY_GUARD` | `false` | Suppress multi-node re-fanout for sync-originated events |
 | `:limits` | `PARRHESIA_LIMITS_*` | see table below | Runtime override group |
 | `:policies` | `PARRHESIA_POLICIES_*` | see table below | Runtime override group |
 | `:listeners` | config-file driven | see notes below | Ingress listeners with bind, transport, feature, auth, network, and baseline ACL settings |

config/config.exs

@@ -39,7 +39,8 @@ config :parrhesia,
   ],
   sync: [
     path: nil,
-    start_workers?: true
+    start_workers?: true,
+    relay_guard: false
   ],
   limits: [
     max_frame_bytes: 1_048_576,

config/runtime.exs

@@ -161,6 +161,7 @@ if config_env() == :prod do
   retention_defaults = Application.get_env(:parrhesia, :retention, [])
   features_defaults = Application.get_env(:parrhesia, :features, [])
   acl_defaults = Application.get_env(:parrhesia, :acl, [])
+  sync_defaults = Application.get_env(:parrhesia, :sync, [])
 
   default_pool_size = Keyword.get(repo_defaults, :pool_size, 32)
   default_queue_target = Keyword.get(repo_defaults, :queue_target, 1_000)
@@ -748,7 +749,12 @@ if config_env() == :prod do
       start_workers?:
         bool_env.(
           "PARRHESIA_SYNC_START_WORKERS",
-          Keyword.get(Application.get_env(:parrhesia, :sync, []), :start_workers?, true)
+          Keyword.get(sync_defaults, :start_workers?, true)
+        ),
+      relay_guard:
+        bool_env.(
+          "PARRHESIA_SYNC_RELAY_GUARD",
+          Keyword.get(sync_defaults, :relay_guard, false)
         )
     ],
     moderation_cache_enabled:

lib/parrhesia/api/events.ex

@@ -87,7 +87,7 @@ defmodule Parrhesia.API.Events do
         end
 
       Dispatcher.dispatch(event)
-      maybe_publish_multi_node(event)
+      maybe_publish_multi_node(event, context)
 
       {:ok,
        %PublishResult{
@@ -312,9 +312,15 @@ defmodule Parrhesia.API.Events do
     end
   end
 
-  defp maybe_publish_multi_node(event) do
-    MultiNode.publish(event)
-    :ok
+  defp maybe_publish_multi_node(event, %RequestContext{} = context) do
+    relay_guard? = Parrhesia.Config.get([:sync, :relay_guard], false)
+
+    if relay_guard? and context.caller == :sync do
+      :ok
+    else
+      MultiNode.publish(event)
+      :ok
+    end
   catch
     :exit, _reason -> :ok
   end

test/parrhesia/api/events_test.exs

@@ -30,6 +30,45 @@ defmodule Parrhesia.API.EventsTest do
     assert second_result.message == "duplicate: event already stored"
   end
 
+  test "publish fanout includes sync-originated events when relay guard is disabled" do
+    with_sync_relay_guard(false)
+    join_multi_node_group!()
+
+    event = valid_event()
+    event_id = event["id"]
+
+    assert {:ok, %{accepted: true}} =
+             Events.publish(event, context: %RequestContext{caller: :sync})
+
+    assert_receive {:remote_fanout_event, %{"id" => ^event_id}}, 200
+  end
+
+  test "publish fanout skips sync-originated events when relay guard is enabled" do
+    with_sync_relay_guard(true)
+    join_multi_node_group!()
+
+    event = valid_event()
+    event_id = event["id"]
+
+    assert {:ok, %{accepted: true}} =
+             Events.publish(event, context: %RequestContext{caller: :sync})
+
+    refute_receive {:remote_fanout_event, %{"id" => ^event_id}}, 200
+  end
+
+  test "publish fanout still includes local-originated events when relay guard is enabled" do
+    with_sync_relay_guard(true)
+    join_multi_node_group!()
+
+    event = valid_event()
+    event_id = event["id"]
+
+    assert {:ok, %{accepted: true}} =
+             Events.publish(event, context: %RequestContext{caller: :local})
+
+    assert_receive {:remote_fanout_event, %{"id" => ^event_id}}, 200
+  end
+
   test "query and count preserve read semantics through the shared API" do
     now = System.system_time(:second)
     first = valid_event(%{"content" => "first", "created_at" => now})
@@ -53,6 +92,36 @@ defmodule Parrhesia.API.EventsTest do
              )
   end
 
+  defp with_sync_relay_guard(enabled?) when is_boolean(enabled?) do
+    [{:config, previous}] = :ets.lookup(Parrhesia.Config, :config)
+
+    sync =
+      previous
+      |> Map.get(:sync, [])
+      |> Keyword.put(:relay_guard, enabled?)
+
+    :ets.insert(Parrhesia.Config, {:config, Map.put(previous, :sync, sync)})
+
+    on_exit(fn ->
+      :ets.insert(Parrhesia.Config, {:config, previous})
+    end)
+  end
+
+  defp join_multi_node_group! do
+    case Process.whereis(:pg) do
+      nil ->
+        case :pg.start_link() do
+          {:ok, _pid} -> :ok
+          {:error, {:already_started, _pid}} -> :ok
+        end
+
+      _pid ->
+        :ok
+    end
+
+    :ok = :pg.join(Parrhesia.Fanout.MultiNode, self())
+  end
+
   defp valid_event(overrides \\ %{}) do
     base_event = %{
       "pubkey" => String.duplicate("1", 64),

test/parrhesia/config_test.exs

@@ -22,6 +22,7 @@ defmodule Parrhesia.ConfigTest do
     assert Parrhesia.Config.get([:limits, :max_filter_limit]) == 500
     assert Parrhesia.Config.get([:database, :separate_read_pool?]) == false
     assert Parrhesia.Config.get([:relay_url]) == "ws://localhost:4413/relay"
+    assert Parrhesia.Config.get([:sync, :relay_guard]) == false
     assert Parrhesia.Config.get([:policies, :auth_required_for_writes]) == false
     assert Parrhesia.Config.get([:policies, :marmot_media_max_imeta_tags_per_event]) == 8
     assert Parrhesia.Config.get([:policies, :marmot_media_reject_mip04_v1]) == true