docs: architecture (#331)

Author: joyc-bq

aws_advanced_python_wrapper/host_list_provider.py

@@ -144,7 +144,7 @@ class RdsHostListProvider(DynamicHostListProvider, HostListProvider):
     # cluster IDs so that connections to the same clusters can share topology info.
     _cluster_ids_to_update: CacheMap[str, str] = CacheMap()
 
-    _executor: ClassVar[Executor] = ThreadPoolExecutor(thread_name_prefix="AuroraHostListProviderExecutor")
+    _executor: ClassVar[Executor] = ThreadPoolExecutor(thread_name_prefix="RdsHostListProviderExecutor")
 
     def __init__(self, host_list_provider_service: HostListProviderService, props: Properties):
         self._host_list_provider_service: HostListProviderService = host_list_provider_service
@@ -474,7 +474,7 @@ def identify_connection(self, connection: Optional[Connection]) -> Optional[Host
         :return: a :py:class:`HostInfo` object containing host information for the given connection.
         """
         if connection is None:
-            raise AwsWrapperError(Messages.get("AuroraHostListProvider.ErrorIdentifyConnection"))
+            raise AwsWrapperError(Messages.get("RdsHostListProvider.ErrorIdentifyConnection"))
 
         driver_dialect = self._host_list_provider_service.driver_dialect
         try:

aws_advanced_python_wrapper/resources/aws_advanced_python_wrapper_messages.properties

@@ -14,8 +14,6 @@
 # limitations under the License.
 
 
-AuroraHostListPlugin.ProviderAlreadySet=[AuroraHostListPlugin]Another dynamic host list provider has already been set: {}.
-
 AuroraPgDialect.HasExtensionsTrue=[AuroraPgDialect] has_extensions: True
 AuroraPgDialect.HasTopologyTrue=[AuroraPgDialect] has_topology: True
 

docs/development-guide/Architecture.md

@@ -0,0 +1,26 @@
+# Architecture
+
+<div style="center"><img src="../images/architecture_user_application.png" alt="diagram on how plugin manager is integrated with the user application"/></div>
+
+The AWS Advanced Python Driver contains 4 main components:
+
+1. The [connection plugin manager](./PluginManager.md)
+2. The [loadable and extensible plugins](./LoadablePlugins.md)
+3. The [plugin service](./PluginService.md)
+4. The host list providers
+
+The connection plugin manager handles all the loaded or registered plugins and sends the Python method call to be executed by all plugins [**subscribed**](./LoadablePlugins.md#subscribed-methods) to that method.
+
+During execution, plugins may utilize the plugin service to help its execution by retrieving or updating:
+
+- the current connection
+- the hosts information or topology of the database
+
+> **NOTES**:
+>
+> - Each Python Connection object has its own instances of:
+>   - plugin manager
+>   - plugin service
+>   - loaded plugin classes
+> - Multiple Python Connection objects opened to the same database server will have separate sets of instances mentioned above.
+> - All plugins share the same instance of plugin service and the same instance of host list provider.