feat(config): allow tuning pool pings, checkout retries and connection recycling

lib/event_store/config.ex

@@ -115,6 +115,7 @@ defmodule EventStore.Config do
     :backoff_max,
     :backoff_min,
     :backoff_type,
+    :checkout_retries,
     :configure,
     :connect_timeout,
     :connection_listeners,
@@ -124,6 +125,8 @@ defmodule EventStore.Config do
     :handshake_timeout,
     :hostname,
     :idle_interval,
+    :idle_limit,
+    :max_lifetime,
     :max_restarts,
     :max_seconds,
     :parameters,
@@ -148,8 +151,12 @@ defmodule EventStore.Config do
     :username
   ]
 
+  # Only the main pool may recycle connections, every other connection holds
+  # state tied to its lifetime (advisory locks, LISTEN registrations).
   def default_postgrex_opts(config) do
-    Keyword.take(config, @postgrex_connection_opts)
+    config
+    |> Keyword.take(@postgrex_connection_opts)
+    |> Keyword.delete(:max_lifetime)
   end
 
   def postgrex_opts(config, name) do

mix.exs

@@ -38,6 +38,7 @@ defmodule EventStore.Mixfile do
 
   defp deps do
     [
+      {:db_connection, "~> 2.10"},
       {:gen_stage, "~> 1.2"},
       {:postgrex, "~> 0.22"},
       {:telemetry, "~> 1.0"},

test/config_test.exs

@@ -190,6 +190,40 @@ defmodule EventStore.ConfigTest do
            ]
   end
 
+  describe "connection pool options" do
+    setup do
+      config =
+        Config.parse(
+          url: "postgres://username:password@localhost/database",
+          checkout_retries: 5,
+          idle_limit: 2,
+          max_lifetime: 480_000..540_000
+        )
+
+      [config: config]
+    end
+
+    test "main pool accepts every option", %{config: config} do
+      opts = Config.postgrex_opts(config, :name)
+
+      assert opts[:checkout_retries] == 5
+      assert opts[:idle_limit] == 2
+      assert opts[:max_lifetime] == 480_000..540_000
+    end
+
+    test "connections other than the main pool are never recycled", %{config: config} do
+      for opts <- [
+            Config.default_postgrex_opts(config),
+            Config.advisory_locks_postgrex_opts(config),
+            Config.postgrex_notifications_opts(config, :name)
+          ] do
+        assert opts[:checkout_retries] == 5
+        assert opts[:idle_limit] == 2
+        refute Keyword.has_key?(opts, :max_lifetime)
+      end
+    end
+  end
+
   test "parse url with query parameters" do
     config = [
       url: "postgres://username:password@localhost/database?ssl=true&pool_size=5&timeout=120000"