feature: implement clustering (#280)

.github/workflows/on_push_branch__execute_ci_cd.yml

@@ -15,7 +15,7 @@ jobs:
     # Currently, this need to be synced manually with the Dockerfile. In the future, the workflow should be changed,
     # so that a development container is built from the Dockerfile, pushed, and then re-used in the following steps.
     # This would also remove the need to install cmake manually in each step:
-    container: hexpm/elixir:1.15.2-erlang-26.0.2-debian-bullseye-20230612-slim
+    container: hexpm/elixir:1.15.7-erlang-26.2.2-debian-bullseye-20240130-slim
 
     steps:
       # See https://github.com/actions/checkout

config/runtime.exs

@@ -108,6 +108,22 @@ if config_env() != :test do
   #
   if config_env() == :prod do
     config :mindwendel, MindwendelWeb.Endpoint, server: true
+
+    # Enable libcluster if set:
+    if System.get_env("MW_ENABLE_LIBCLUSTER") == "true" do
+      Logger.info("Configuring libcluster to use Kubernetes.DNS strategy")
+
+      config :libcluster,
+        topologies: [
+          k8s_mindwendel: [
+            strategy: Elixir.Cluster.Strategy.Kubernetes.DNS,
+            config: [
+              service: "mindwendel-cluster",
+              application_name: "mindwendel"
+            ]
+          ]
+        ]
+    end
   end
 
   #

lib/mindwendel/application.ex

@@ -38,6 +38,19 @@ defmodule Mindwendel.Application do
       {Oban, oban_config()}
     ]
 
+    children =
+      if Application.get_env(:libcluster, :topologies) do
+        Logger.info("Adding Cluster.Supervisor to Supervisor tree")
+
+        children ++
+          [
+            {Cluster.Supervisor,
+             [Application.get_env(:libcluster, :topologies), [name: Mindwendel.ClusterSupervisor]]}
+          ]
+      else
+        children
+      end
+
     # when logger_json is defined, we also want it to take care of ecto:
     if Application.get_env(:qrstorage, :logger_json) do
       :ok =

mix.exs

@@ -63,7 +63,8 @@ defmodule Mindwendel.MixProject do
       {:telemetry_metrics, "1.0.0"},
       {:telemetry_poller, "1.0.0"},
       {:timex, "3.7.11"},
-      {:logger_json, "5.1.4"}
+      {:logger_json, "5.1.4"},
+      {:libcluster, "3.3.3"}
     ]
   end
 

mix.lock

@@ -23,6 +23,7 @@
   "httpoison": {:hex, :httpoison, "2.2.1", "87b7ed6d95db0389f7df02779644171d7319d319178f6680438167d7b69b1f3d", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "51364e6d2f429d80e14fe4b5f8e39719cacd03eb3f9a9286e61e216feac2d2df"},
   "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~> 0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
   "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
+  "libcluster": {:hex, :libcluster, "3.3.3", "a4f17721a19004cfc4467268e17cff8b1f951befe428975dd4f6f7b84d927fe0", [:mix], [{:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "7c0a2275a0bb83c07acd17dab3c3bfb4897b145106750eeccc62d302e3bdfee5"},
   "logger_json": {:hex, :logger_json, "5.1.4", "9e30a4f2e31a8b9e402bdc20bd37cf9b67d3a31f19d0b33082a19a06b4c50f6d", [:mix], [{:ecto, "~> 2.1 or ~> 3.0", [hex: :ecto, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:phoenix, ">= 1.5.0", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: true]}], "hexpm", "3f20eea58e406a33d3eb7814c7dff5accb503bab2ee8601e84da02976fa3934c"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
   "mime": {:hex, :mime, "2.0.5", "dc34c8efd439abe6ae0343edbb8556f4d63f178594894720607772a041b04b02", [:mix], [], "hexpm", "da0d64a365c45bc9935cc5c8a7fc5e49a0e0f9932a761c55d6c52b142780a05c"},

rel/overlays/bin/server

@@ -10,4 +10,14 @@ done
 
 ./mindwendel eval "Mindwendel.Release.migrate"
 
+# This is required for libcluster, see https://hexdocs.pm/libcluster/Cluster.Strategy.Kubernetes.DNS.html
+if [ -n "$POD_IP" ]; then
+  echo "Setting variables for libcluster"
+  export RELEASE_DISTRIBUTION=name
+  export RELEASE_NODE=mindwendel@${POD_IP}
+else
+  echo "Not setting variables for libcluster"
+fi
+
+
 PHX_SERVER=true exec ./mindwendel start