[DPE-5764] handle config as dict (#4)

This PR improves the handling of config properties. Instead of using a
list of strings, the config is loaded from a yaml-file and handled as a
dict. This allows for controlling all config properties as part of the
code while making it easier to add or update config properties. It also
provides a cleaner approach.

Key changes:
- move config properties to a separate file
- load config properties from yaml to dict instead of from string to
list of strings
- `config_properties` now returns a string instead of `list[str]` which
makes it easier to write to a file

src/managers/config.py

@@ -5,7 +5,9 @@
 """Manager for handling configuration building + writing."""
 
 import logging
+from pathlib import Path
 
+import yaml
 from ops.model import ConfigData
 
 from core.cluster import ClusterState
@@ -14,52 +16,7 @@
 
 logger = logging.getLogger(__name__)
 
-DEFAULT_PROPERTIES = """
-initial-cluster-token: 'etcd-cluster'
-snapshot-count: 10000
-heartbeat-interval: 100
-election-timeout: 1000
-quota-backend-bytes: 0
-max-snapshots: 5
-max-wals: 5
-strict-reconfig-check: false
-enable-pprof: true
-proxy: 'off'
-proxy-failure-wait: 5000
-proxy-refresh-interval: 30000
-proxy-dial-timeout: 1000
-proxy-write-timeout: 5000
-proxy-read-timeout: 0
-force-new-cluster: false
-auto-compaction-mode: periodic
-auto-compaction-retention: "1"
-"""
-
-# these config properties are not used at the moment
-# they are only listed here for completeness
-TLS_PROPERTIES = """
-client-transport-security:
-  cert-file:
-  # Path to the client server TLS key file.
-  key-file:
-  client-cert-auth: false
-  trusted-ca-file:
-  auto-tls: false
-peer-transport-security:
-  cert-file:
-  key-file:
-  client-cert-auth: false
-  trusted-ca-file:
-  auto-tls: false
-  allowed-cn:
-  allowed-hostname:
-cipher-suites: [
-  TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
-  TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
-]
-tls-min-version: 'TLS1.2'
-tls-max-version: 'TLS1.3'
-"""
+WORKING_DIR = Path(__file__).absolute().parent
 
 
 class ConfigManager:
@@ -77,28 +34,29 @@ def __init__(
         self.config_file = CONFIG_FILE
 
     @property
-    def config_properties(self) -> list[str]:
+    def config_properties(self) -> str:
         """Assemble the config properties.
 
         Returns:
             List of properties to be written to the config file.
         """
-        properties = [
-            f"name: {self.state.unit_server.member_name}",
-            f"initial-advertise-peer-urls: {self.state.unit_server.peer_url}",
-            f"initial-cluster-state: {self.state.cluster.initial_cluster_state}",
-            f"listen-peer-urls: {self.state.unit_server.peer_url}",
-            f"listen-client-urls: {self.state.unit_server.client_url}",
-            f"advertise-client-urls: {self.state.unit_server.client_url}",
-            f"initial-cluster: {self._get_cluster_endpoints()}",
-        ] + DEFAULT_PROPERTIES.split("\n")
-
-        return properties
+        with open(f"{WORKING_DIR}/config/etcd.conf.yml") as config:
+            config_properties = yaml.safe_load(config)
+
+        config_properties["name"] = self.state.unit_server.member_name
+        config_properties["initial-advertise-peer-urls"] = self.state.unit_server.peer_url
+        config_properties["initial-cluster-state"] = self.state.cluster.initial_cluster_state
+        config_properties["listen-peer-urls"] = self.state.unit_server.peer_url
+        config_properties["listen-client-urls"] = self.state.unit_server.client_url
+        config_properties["advertise-client-urls"] = self.state.unit_server.client_url
+        config_properties["initial-cluster"] = self._get_cluster_endpoints()
+
+        return yaml.safe_dump(config_properties)
 
     def set_config_properties(self) -> None:
         """Write the config properties to the config file."""
         self.workload.write_file(
-            content="\n".join(self.config_properties),
+            content=self.config_properties,
             file=self.config_file,
         )
 

src/managers/config/etcd.conf.yml

@@ -0,0 +1,24 @@
+initial-cluster-token: 'etcd-cluster'
+snapshot-count: 10000
+heartbeat-interval: 100
+election-timeout: 1000
+quota-backend-bytes: 0
+max-snapshots: 5
+max-wals: 5
+strict-reconfig-check: false
+enable-pprof: true
+proxy: 'off'
+proxy-failure-wait: 5000
+proxy-refresh-interval: 30000
+proxy-dial-timeout: 1000
+proxy-write-timeout: 5000
+proxy-read-timeout: 0
+force-new-cluster: false
+auto-compaction-mode: periodic
+auto-compaction-retention: "1"
+cipher-suites: [
+  TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+  TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
+]
+tls-min-version: 'TLS1.2'
+tls-max-version: 'TLS1.3'