Added documentation

README.md

@@ -288,15 +288,16 @@ Configuration can be set using environment variables
 | `DWN_REGISTRATION_PROOF_OF_WORK_ENABLED`          | Require new users to complete a proof-of-work challenge                                                                 | `false`                |
 | `DWN_REGISTRATION_PROOF_OF_WORK_INITIAL_MAX_HASH` | Initial maximum allowed hash in 64 char HEX string. The more leading zeros (smaller number) the higher the difficulty.  | `false`                |
 | `DWN_STORAGE`                                     | URL to use for storage by default. See [Storage Options](#storage-options) for details                                  | `level://data`         |
-| `DWN_STORAGE_MESSAGES`                            | URL to use for storage of messages.                                                                                     | value of `DWN_STORAGE` |
-| `DWN_STORAGE_DATA`                                | URL to use for data storage                                                                                             | value of `DWN_STORAGE` |
-| `DWN_STORAGE_EVENTS`                              | URL to use for event storage                                                                                            | value of `DWN_STORAGE` |
+| `DWN_STORAGE_MESSAGES`                            | Connection URL or file path to custom plugin to use for the message store.                                              | value of `DWN_STORAGE` |
+| `DWN_STORAGE_DATA`                                | Connection URL or file path to custom plugin to use for the data store.                                                 | value of `DWN_STORAGE` |
+| `DWN_STORAGE_RESUMABLE_TASKS`                     | Connection URL or file path to custom plugin to use for the resumable task store.                                       | value of `DWN_STORAGE` |
+| `DWN_STORAGE_EVENTS`                              | Connection URL or file path to custom plugin to use for the event store.                                                | value of `DWN_STORAGE` |
 | `DWN_TERMS_OF_SERVICE_FILE_PATH`                  | Required terms of service agreement if set. Value is path to the terms of service file.                                 | unset                  |
 | `DWN_TTL_CACHE_URL`                               | URL of the TTL cache used by the DWN. Currently only supports SQL databases.                                            | `sqlite://`            |
 
 ### Storage Options
 
-Several storage formats are supported, and may be configured with the `DWN_STORAGE_*` environment variables:
+Several built storage options are supported, and may be configured with the `DWN_STORAGE_*` environment variables:
 
 | Database   | Example                                               | Notes                                                                                                                                                                                 |
 | ---------- | ----------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
@@ -305,6 +306,24 @@ Several storage formats are supported, and may be configured with the `DWN_STORA
 | MySQL      | `mysql://user:pass@host/db?debug=true&timezone=-0700` | [all URL options documented here](https://github.com/mysqljs/mysql#connection-options)                                                                                                |
 | PostgreSQL | `postgres:///dwn`                                     | any options other than the URL scheme (`postgres://`) may also be specified via [standard environment variables](https://node-postgres.com/features/connecting#environment-variables) |
 
+### Plugins
+In some scenarios, you may want to provide a custom implementation of a pluggable module for the DWN Server. The following interfaces defined in `dwn-sdk-js` package are supported:
+
+- `DataStore`
+- `MessageStore`
+- `ResumableDataStore`
+- `EventLog`
+- `EventStream`
+
+To load your custom plugin, specify the absolute path to the `.js` file of your custom implementation using the corresponding environment variable. For instance, use `DWN_STORAGE_DATA` for a custom DWN Data Store.
+
+Refer to the `tests/plugins/*.ts` files for examples of plugin implementations. In summary, you need to:
+
+- Implement the corresponding interface from the `dwn-sdk-js` package. For example, implement the `DataStore` interface for a DWN Data Store.
+- Ensure that the built `.js` file that will be referenced by the DWN Server config environment variable contains a class that:
+  1. Is a default export. This is how DWN Server locates the correct class for instantiation.
+  1. Has a public constructor that does not take any arguments. This is how DWN Server instantiates the plugin.
+
 ## Registration Requirements
 
 There are multiple optional registration gates, each of which can be enabled (all are disabled by default). Tenants (DIDs) must comply with whatever

src/plugin-loader.ts

@@ -8,14 +8,8 @@ export class PluginLoader {
   public static async loadPlugin<T>(filePath: string): Promise<T> {
     try {
       const module = await import(filePath);
-
-      // Check if the default export is a class
-      if (typeof module.default === 'function') {
-        const instance: T = new module.default() as T;
-        return instance;
-      } else {
-        throw new Error(`Default export at ${filePath} is not a class.`);
-      }
+      const instance: T = new module.default() as T;
+      return instance;
     } catch (error) {
       throw new Error(`Failed to load component at ${filePath}: ${error.message}`);
     }