Add experimental max_connections config

config.yaml

@@ -402,3 +402,7 @@ options:
       Allowed values are: from 0 to 2000000000.
     type: int
     default: 150000000
+  experimental_max_connections:
+    type: int
+    description: |
+      [EXPERIMENTAL] Force set max_connections.

src/charm.py

@@ -1547,8 +1547,14 @@ def update_config(self, is_creating_backup: bool = False) -> bool:
             logger.warning("Early exit update_config: Cannot connect to Postgresql")
             return False
 
+        # Use config value if set, calculate otherwise
+        if self.config.experimental_max_connections:
+            max_connections = self.config.experimental_max_connections
+        else:
+            max_connections = max(4 * os.cpu_count(), 100)
+
         self._patroni.bulk_update_parameters_controller_by_patroni({
-            "max_connections": max(4 * os.cpu_count(), 100),
+            "max_connections": max_connections,
             "max_prepared_transactions": self.config.memory_max_prepared_transactions,
         })
 

src/config.py

@@ -98,6 +98,7 @@ class CharmConfig(BaseConfigModel):
     vacuum_autovacuum_vacuum_cost_delay: Optional[float]
     vacuum_autovacuum_vacuum_scale_factor: Optional[float]
     vacuum_vacuum_freeze_table_age: Optional[int]
+    experimental_max_connections: Optional[int]
 
     @classmethod
     def keys(cls) -> list[str]: