refactor: remove GenServer behavior from gossip blobsidecar

lib/lambda_ethereum_consensus/beacon/beacon_node.ex

@@ -53,7 +53,6 @@ defmodule LambdaEthereumConsensus.Beacon.BeaconNode do
         LambdaEthereumConsensus.Beacon.PendingBlocks,
         LambdaEthereumConsensus.Beacon.SyncBlocks,
         LambdaEthereumConsensus.P2P.Gossip.Attestation,
-        LambdaEthereumConsensus.P2P.Gossip.BlobSideCar,
         LambdaEthereumConsensus.P2P.Gossip.OperationsCollector,
         {Task.Supervisor, name: PruneStatesSupervisor},
         {Task.Supervisor, name: PruneBlocksSupervisor}

lib/lambda_ethereum_consensus/beacon/sync_blocks.ex

@@ -86,7 +86,7 @@ defmodule LambdaEthereumConsensus.Beacon.SyncBlocks do
   # TODO: handle subscription failures.
   defp start_subscriptions() do
     Gossip.BeaconBlock.subscribe_to_topic()
-    Gossip.BlobSideCar.start()
+    Gossip.BlobSideCar.subscribe_to_topics()
     Gossip.OperationsCollector.start()
   end
 

lib/lambda_ethereum_consensus/p2p/gossip/beacon_block.ex

@@ -38,13 +38,6 @@ defmodule LambdaEthereumConsensus.P2P.Gossip.BeaconBlock do
     :ok
   end
 
-  @spec join_topic() :: :ok
-  def join_topic() do
-    # TODO: this doesn't take into account fork digest changes
-    topic_name = topic()
-    Libp2pPort.join_topic(self(), topic_name)
-  end
-
   @spec subscribe_to_topic() :: :ok | :error
   def subscribe_to_topic() do
     topic()
@@ -59,15 +52,15 @@ defmodule LambdaEthereumConsensus.P2P.Gossip.BeaconBlock do
     end
   end
 
-  ##########################
-  ### Private functions
-  ##########################
-
-  defp topic() do
+  def topic() do
     fork_context = BeaconChain.get_fork_digest() |> Base.encode16(case: :lower)
     "/eth2/#{fork_context}/beacon_block/ssz_snappy"
   end
 
+  ##########################
+  ### Private functions
+  ##########################
+
   @spec validate(SignedBeaconBlock.t(), Types.slot()) :: :ok | {:error, any}
   defp validate(%SignedBeaconBlock{message: block}, current_slot) do
     cond do

lib/lambda_ethereum_consensus/p2p/gossip/blob_sidecar.ex

@@ -7,60 +7,12 @@ defmodule LambdaEthereumConsensus.P2P.Gossip.BlobSideCar do
   alias LambdaEthereumConsensus.P2P.Gossip.Handler
   alias LambdaEthereumConsensus.Store.BlobDb
 
-  use GenServer
-
   require Logger
 
   @behaviour Handler
 
-  @type topics :: [String.t()]
-
-  ##########################
-  ### Public API
-  ##########################
-
-  def start_link(init_arg) do
-    GenServer.start_link(__MODULE__, init_arg, name: __MODULE__)
-  end
-
-  def start() do
-    GenServer.call(__MODULE__, :start)
-  end
-
-  @impl true
-  def handle_gossip_message(topic, msg_id, message) do
-    GenServer.cast(__MODULE__, {:gossipsub, {topic, msg_id, message}})
-  end
-
-  ##########################
-  ### GenServer Callbacks
-  ##########################
-
   @impl true
-  @spec init(any()) :: {:ok, topics()} | {:stop, any()}
-  def init(_init_arg) do
-    # TODO: this doesn't take into account fork digest changes
-    fork_context = BeaconChain.get_fork_digest() |> Base.encode16(case: :lower)
-
-    # Generate blob sidecar topics
-    # NOTE: there's one per blob index in Deneb (6 blobs per block)
-    topics =
-      Enum.map(0..(ChainSpec.get("BLOB_SIDECAR_SUBNET_COUNT") - 1), fn i ->
-        "/eth2/#{fork_context}/blob_sidecar_#{i}/ssz_snappy"
-      end)
-
-    Enum.each(topics, &Libp2pPort.join_topic/1)
-    {:ok, topics}
-  end
-
-  @impl true
-  def handle_call(:start, _from, topics) do
-    Enum.each(topics, fn topic -> Libp2pPort.subscribe_to_topic(topic, __MODULE__) end)
-    {:reply, :ok, topics}
-  end
-
-  @impl true
-  def handle_cast({:gossipsub, {_topic, msg_id, message}}, topics) do
+  def handle_gossip_message(_topic, msg_id, message) do
     with {:ok, uncompressed} <- :snappyer.decompress(message),
          {:ok, %Types.BlobSidecar{index: blob_index} = blob} <-
            Ssz.from_ssz(uncompressed, Types.BlobSidecar) do
@@ -72,7 +24,30 @@ defmodule LambdaEthereumConsensus.P2P.Gossip.BlobSideCar do
         Logger.warning("[Gossip] Blob rejected, reason: #{inspect(reason)}")
         Libp2pPort.validate_message(msg_id, :reject)
     end
+  end
 
-    {:noreply, topics}
+  @spec subscribe_to_topics() :: :ok | {:error, String.t()}
+  def subscribe_to_topics() do
+    Enum.each(topics(), fn topic ->
+      case Libp2pPort.subscribe_to_topic(topic, __MODULE__) do
+        :ok ->
+          :ok
+
+        {:error, reason} ->
+          Logger.error("[Gossip] Subscription failed: '#{reason}'")
+          {:error, reason}
+      end
+    end)
+  end
+
+  def topics() do
+    # TODO: this doesn't take into account fork digest changes
+    fork_context = BeaconChain.get_fork_digest() |> Base.encode16(case: :lower)
+
+    # Generate blob sidecar topics
+    # NOTE: there's one per blob index in Deneb (6 blobs per block)
+    Enum.map(0..(ChainSpec.get("BLOB_SIDECAR_SUBNET_COUNT") - 1), fn i ->
+      "/eth2/#{fork_context}/blob_sidecar_#{i}/ssz_snappy"
+    end)
   end
 end

lib/libp2p_port.ex

@@ -11,6 +11,7 @@ defmodule LambdaEthereumConsensus.Libp2pPort do
 
   alias LambdaEthereumConsensus.Beacon.BeaconChain
   alias LambdaEthereumConsensus.P2P.Gossip.BeaconBlock
+  alias LambdaEthereumConsensus.P2P.Gossip.BlobSideCar
   alias LambdaEthereumConsensus.StateTransition.Misc
   alias LambdaEthereumConsensus.Utils.BitVector
   alias Types.EnrForkId
@@ -266,8 +267,22 @@ defmodule LambdaEthereumConsensus.Libp2pPort do
     cast_command(pid, {:update_enr, enr})
   end
 
-  defp join_init_topics() do
-    BeaconBlock.join_topic()
+  @spec join_init_topics(port()) :: :ok | {:error, String.t()}
+  defp join_init_topics(port) do
+    topics = [BeaconBlock.topic()] ++ BlobSideCar.topics()
+
+    topics
+    |> Enum.each(fn topic_name ->
+      c = {:join, %JoinTopic{name: topic_name}}
+      data = Command.encode(%Command{c: c})
+
+      send_data(port, data)
+
+      :telemetry.execute([:port, :message], %{}, %{
+        function: "join_topic",
+        direction: "elixir->"
+      })
+    end)
   end
 
   ########################
@@ -288,7 +303,7 @@ defmodule LambdaEthereumConsensus.Libp2pPort do
     |> InitArgs.encode()
     |> then(&send_data(port, &1))
 
-    if join_init_topics, do: join_init_topics()
+    if join_init_topics, do: join_init_topics(port)
 
     {:ok, %{port: port, new_peer_handler: new_peer_handler, subscriptors: %{}}}
   end
@@ -443,6 +458,7 @@ defmodule LambdaEthereumConsensus.Libp2pPort do
     |> then(&struct!(InitArgs, &1))
   end
 
+  @spec send_data(port(), iodata()) :: boolean()
   defp send_data(port, data), do: Port.command(port, data)
 
   defp send_protobuf(pid, %mod{} = protobuf) do