[DPE-7549] Add compression and restore max-process (#1019)

* Add compression and restore max-process

* Bump libs

* Use available resources

Author: dragomirp

lib/charms/data_platform_libs/v0/data_interfaces.py

@@ -331,7 +331,7 @@ def _on_topic_requested(self, event: TopicRequestedEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 47
+LIBPATCH = 48
 
 PYDEPS = ["ops>=2.0.0"]
 
@@ -3760,6 +3760,10 @@ def _on_relation_changed_event(self, event: RelationChangedEvent) -> None:
                 event.relation, app=event.app, unit=event.unit
             )
 
+    def _on_secret_changed_event(self, event: SecretChangedEvent) -> None:
+        """Event emitted when the relation data has changed."""
+        pass
+
 
 class OpenSearchProvides(OpenSearchProvidesData, OpenSearchProvidesEventHandlers):
     """Provider-side of the OpenSearch relation."""

src/backups.py

@@ -1186,6 +1186,7 @@ def _render_pgbackrest_conf_file(self) -> bool:
         # Open the template pgbackrest.conf file.
         with open("templates/pgbackrest.conf.j2") as file:
             template = Template(file.read())
+        cpu_count, _ = self.charm.get_available_resources()
         # Render the template file with the correct values.
         rendered = template.render(
             enable_tls=self.charm.is_tls_enabled and len(self.charm.peer_members_endpoints) > 0,
@@ -1202,6 +1203,7 @@ def _render_pgbackrest_conf_file(self) -> bool:
             storage_path=self.charm._storage_path,
             user=BACKUP_USER,
             retention_full=s3_parameters["delete-older-than-days"],
+            process_max=max(cpu_count - 2, 1),
         )
         # Delete the original file and render the one with the right info.
         filename = "/etc/pgbackrest.conf"

templates/pgbackrest.conf.j2

@@ -1,5 +1,6 @@
 [global]
 backup-standby=y
+compress-type=zst
 repo1-retention-full-type=time
 repo1-retention-full={{ retention_full }}
 repo1-retention-history=365
@@ -43,3 +44,6 @@ pg{{ ns.count }}-user={{ user }}
 {% set ns.count = ns.count + 1 %}
 {%- endfor %}
 {%- endif %}
+
+[global:restore]
+process-max={{process_max}}

tests/unit/test_backups.py

@@ -1761,6 +1761,7 @@ def test_render_pgbackrest_conf_file(harness, tls_ca_chain_filename):
             new_callable=PropertyMock(return_value=tls_ca_chain_filename),
         ) as _tls_ca_chain_filename,
         patch("charm.PostgreSQLBackups._retrieve_s3_parameters") as _retrieve_s3_parameters,
+        patch("charm.PostgresqlOperatorCharm.get_available_resources", return_value=(4, 1024)),
     ):
         # Set up a mock for the `open` method, set returned data to postgresql.conf template.
         with open("templates/pgbackrest.conf.j2") as f:
@@ -1812,6 +1813,7 @@ def test_render_pgbackrest_conf_file(harness, tls_ca_chain_filename):
             storage_path=harness.charm._storage_path,
             user="backup",
             retention_full=30,
+            process_max=2,
         )
 
         # Patch the `open` method with our mock.