From 6e9c60c610963a1bf18626749a17f914ab318de5 Mon Sep 17 00:00:00 2001
From: Aayush Kumar Sahu <aayushmau5@gmail.com>
Date: Sun, 24 Mar 2024 21:29:04 +0530
Subject: [PATCH] add remote connection script and remote node task runner

---
 elixir_cluster_with_remote_flyio | 80 ++++++++++++++++++++++++++++++++
 lib/battleship/task_runner.ex    | 41 ++++++++++++++++
 2 files changed, 121 insertions(+)
 create mode 100755 elixir_cluster_with_remote_flyio
 create mode 100644 lib/battleship/task_runner.ex

diff --git a/elixir_cluster_with_remote_flyio b/elixir_cluster_with_remote_flyio
new file mode 100755
index 0000000..7bf2f1b
--- /dev/null
+++ b/elixir_cluster_with_remote_flyio
@@ -0,0 +1,80 @@
+#!/bin/bash
+
+# After opening a WireGuard connection to your Fly.io network, copy this file
+# into the directory for your Elixir application. Run the script to start the
+# local Elixir project and cluster it to an application running on Fly.io.
+
+# In order for this to work:
+# - Your wireguard connection must be up.
+# - When run from a directory with a `fly.toml` file, `flyctl` command is used
+#   to access information about the application.
+# - Set the ENV `CLUSTER_APP_NAME` to specify a different hosted app name.
+# - Set the ENV `RELEASE_COOKIE` to override the Erlang cookie used for
+#   clustering. It uses the the value from the deployed app if it is set there.
+# - Run the script.
+
+set -e
+
+if ! command -v jq &> /dev/null; then
+    echo "jq is not installed. Please install it before running this script. It is a command-line JSON processor."
+    exit 1
+fi
+
+# Check if CLUSTER_APP_NAME is set and use it if found
+if [[ -n $CLUSTER_APP_NAME ]]; then
+    # Use the override app_name from the ENV
+    json_data=$(fly status --app ${CLUSTER_APP_NAME} --json)
+else
+    # Use the app_name for the current app
+    json_data=$(fly status --json)
+fi
+
+# Use an explicit RELEASE_COOKIE value if provided
+if [ -n "$RELEASE_COOKIE" ]; then
+    release_cookie=$RELEASE_COOKIE
+else
+    # Extract the RELEASE_COOKIE value from the deployed app
+    release_cookie=$(echo "$json_data" | jq -r '.Machines[] | select(.state == "started") | .config | .env | .RELEASE_COOKIExxx' | head -n 1)
+
+    if [ $release_cookie == "null" ]; then
+        echo "The deployed application did not set RELEASE_COOKIE ENV. If the cookie is static on the server, provide it locally through RELEASE_COOKIE."
+        exit 1
+    fi
+fi
+
+# Extract the app_name
+app_name=$(echo "$json_data" | jq -r '.Name')
+
+# Extract private_ip for the first started machine
+private_ip=$(echo "$json_data" | jq -r '.Machines[] | select(.state == "started") | .private_ip' | head -n 1)
+
+# Extract image_ref tag hash for the first started machine
+image_tags=$(echo "$json_data" | jq -r '.Machines[] | select(.state == "started") | .image_ref.tag | sub("deployment-"; "")' | head -n 1)
+
+if [ -z "$private_ip" ]; then
+    echo "No instances appear to be running at this time."
+    exit 1
+fi
+
+# Assemble the full node name
+full_node_name="${app_name}@${private_ip}"
+echo Attempting to connect to $full_node_name
+
+# IMPORTANT:
+# ==========
+# Fly.io uses an IPv6 network internally for private IPs. The BEAM needs IPv6
+# support to be enabled explicitly.
+#
+# The issue is, if it's enabled globally like in a `.bashrc` file, then setting
+# it here essentially flips it OFF. If not set globally, then it should be set
+# here. Choose the version that fits your situation.
+#
+# It's the `--erl "-proto_dist inet6_tcp"` portion.
+
+# export ERL_AFLAGS="-kernel shell_history enabled -proto_dist inet6_tcp"
+
+# Toggles on IPv6 support for the local node being started.
+iex --erl "-proto_dist inet6_tcp" --sname local-battleship --cookie ${release_cookie} -e "IO.inspect(Node.connect(:'${full_node_name}'), label: \"Node Connected?\"); IO.inspect(Node.list(), label: \"Connected Nodes\")"
+
+# Does NOT toggle on IPv6 support, assuming it is enabled some other way.
+# iex --sname local --cookie ${release_cookie} --hidden -e "IO.inspect(Node.connect(:'${full_node_name}'), label: \"Node Connected?\"); IO.inspect(Node.list(:hidden), label: \"Connected Nodes\")" -S mix phx.server
diff --git a/lib/battleship/task_runner.ex b/lib/battleship/task_runner.ex
new file mode 100644
index 0000000..8a05f0b
--- /dev/null
+++ b/lib/battleship/task_runner.ex
@@ -0,0 +1,41 @@
+defmodule Battleship.TaskRunner do
+  require Logger
+
+  @remote_node_name "phoenix-aayushsahu-com"
+
+  def get_task_runner_node() do
+    Node.list()
+    |> Enum.find(nil, fn node_name ->
+      node_name
+      |> Atom.to_string()
+      |> String.contains?(@remote_node_name)
+    end)
+  end
+
+  def run(task_info, remote_node) do
+    %{module: module, function: function, args: args} = task_info
+
+    Task.async(fn ->
+      Process.flag(:trap_exit, true)
+
+      _t2 =
+        Task.Supervisor.async_nolink(
+          # Accumulator.TaskRunner is a task supervisor that's running on remote node
+          {Accumulator.TaskRunner, remote_node},
+          module,
+          function,
+          args
+        )
+
+      receive do
+        {:DOWN, _, _, pid, _reason} ->
+          Logger.error("Task execution failed with PID: #{pid}")
+          nil
+
+        {_ref, result} ->
+          result
+      end
+    end)
+    |> Task.await()
+  end
+end