feat: add keepalive option

add a wrapper around the keepalive transport option, which is enabled
by default as it resolves a connection issue with scylla cloud

mimics astarte-platform/astarte_data_access#126

Signed-off-by: Francesco Noacco <francesco.noacco@secomind.com>

Author: noaccOS

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [1.3.0] - Unreleased
+### Added
+- Add the option to enable keepalive for scylladb connections, using the environment variable
+  `DOCKER_VERNEMQ_ASTARTE_VMQ_PLUGIN__CASSANDRA__ENABLE_KEEPALIVE`. Defaults to `true`
+
 ## [1.2.1-rc.0] 2025-08-22
 ### Changed
 - RPC now uses erlang clustering instead of `astarte_rpc`

lib/astarte_vmq_plugin/config.ex

@@ -182,22 +182,31 @@ defmodule Astarte.VMQ.Plugin.Config do
 
   def xandra_options! do
     # TODO handle SNI
+    keepalive =
+      case Application.get_env(:astarte_vmq_plugin, :cassandra_enable_keepalive, "true") do
+        "true" -> true
+        _ -> false
+      end
+
+    transport_options =
+      xandra_ssl_options()
+      |> Keyword.put(:keepalive, keepalive)
+
     [
       nodes: Application.get_env(:astarte_vmq_plugin, :cassandra_nodes),
       authentication: xandra_authentication_options(),
       pool_size: Application.get_env(:astarte_vmq_plugin, :cassandra_pool_size, 10),
       encryption: Application.get_env(:astarte_vmq_plugin, :cassandra_ssl_enabled, false),
+      transport_options: transport_options,
       name: :xandra
     ]
-    |> populate_xandra_ssl_options!()
   end
 
-  defp populate_xandra_ssl_options!(options) do
+  defp xandra_ssl_options do
     if Application.get_env(:astarte_vmq_plugin, :cassandra_ssl_enabled, false) do
-      ssl_options = build_xandra_ssl_options!()
-      Keyword.put(options, :transport_options, ssl_options)
+      build_xandra_ssl_options!()
     else
-      options
+      []
     end
   end
 

priv/astarte_vmq_plugin.schema

@@ -145,6 +145,11 @@
         {datatype, string}
   ]}.
 
+{mapping, "astarte_vmq_plugin.cassandra.enable_keepalive", "astarte_vmq_plugin.cassandra_enable_keepalive", [
+    {datatype, {enum, [true, false]}},
+    {default, true}
+  ]}.
+
 {translation, "astarte_vmq_plugin.registry_mfa",
   fun(Conf) ->
     S = cuttlefish:conf_get("astarte_vmq_plugin.registry_mfa", Conf),