I've been observing increasing memory usages since upgrading to the out-of-tree barman-cloud plugin (on v1.26.0);
I've been suspicions before, but after more investigation I wanted to raise awareness more formally:

• only the primary instance seems to be suffering from the memory leak (which is doing the WAL shipping)
• from what I'm seeing, it seems to be the plugin-barman-cloud container that's increasing its memory slowly, but steadily; a good metric I've found is container_memory_working_set_bytes{container="plugin-barman-cloud"}
• possible workarounds are given by failovering, restarting the cluster, albeit that might be overkill

Before and after migrating to the out-of-tree plugin:

3-node HA cluster, which was restarted and is starting to accumulate memory again; running out-of-tree for the whole duration of the graph:

Different 3-node HA cluster which was migrated to out-of-tree on 03.06.25 00:00, also starting to increase memory consumption:

container_memory_working_set_bytes{container="plugin-barman-cloud"} is the culprit