From f99e407d6e6fd6c52867706396af5ad30205101e Mon Sep 17 00:00:00 2001
From: Dragomir Penev <dragomir.penev@canonical.com>
Date: Mon, 20 May 2024 20:37:04 +0300
Subject: [PATCH] Add experimental max_connections config

---
 config.yaml   | 4 ++++
 src/charm.py  | 8 +++++++-
 src/config.py | 1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/config.yaml b/config.yaml
index 158ef85875..35617edbab 100644
--- a/config.yaml
+++ b/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.
diff --git a/src/charm.py b/src/charm.py
index 67eb66ae4a..ab887a52ee 100755
--- a/src/charm.py
+++ b/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,
         })
 
diff --git a/src/config.py b/src/config.py
index 6627a67b32..c8196b46ba 100644
--- a/src/config.py
+++ b/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]: