Load plugin list from files/plugins.conf

PLUGINS.md

@@ -8,9 +8,7 @@ Typical use cases include, but are not limited to, rewriting prefixes to improve
 
 ## Usage
 
-List the directories of plugins to be used in `plugin.conf`. If the line starts with `#`, it is treated as a comment and ignored.
-
-Then specify the path to `plugin.conf` to `PLUGINS` environment variable when starting the SPARQL-proxy. For example, `PLUGINS=/path/to/plugin.conf`. This will activate the plugin mechanism.
+List the directories of plugins to be used in `files/plugin.conf`. If the line starts with `#`, it is treated as a comment and ignored.
 
 Note that plugins are applied in the order specified in this file. That is, the first plugin in the list receives from the request from the client, then next plugin receives the request from the previous plugin, and so on. Responses are processed in the reverse order.
 
@@ -40,17 +38,18 @@ plugins
     └── main.ts
 ```
 
-Create `plugins.conf` which contains the path to the `noop` plugin:
+Create `files/plugins.conf` which contains the path to the `noop` plugin:
 
 ```
+# files/plugins.conf
 ./plugins/noop
 ```
 
-Then start the SPARQL-proxy with `PLUGINS` environment variable:
+Then start SPARQL-proxy:
 
 
 ```
-❯ PLUGINS=./plugins.conf SPARQL_BACKEND=https://example.com/sparql npm start
+❯ SPARQL_BACKEND=https://example.com/sparql npm start
 
 > [email protected] start
 > tsx src/server.mjs

README.md

@@ -214,16 +214,6 @@ Set `true` to enable passthrough mode. If enabled, queries are sent to the backe
 
 You should enable this feature only when you understand exactly what you are doing.
 
-### `PLUGINS`
-
-THIS IS AN EXPERIMENTAL FEATURE.
-
-(default: none)
-
-Set the path to the plugins configuration file. List the paths of the plugins to be used in this file in the order you want to apply them.
-
-This feature does not work with the query splitting mode and the passthrough mode.
-
 ## Serving SPARQL Service Description
 
 If you want to serve SPARQL service description, put the descriptions under `files` directory with the name `description.[format]`.
@@ -235,6 +225,15 @@ NOTE: If you're running `sparql-proxy` within Docker, you may want to use `-v` o
     $ docker run -p 8080:3000 -e SPARQL_BACKEND=http://example.com/sparql -v `pwd`/files:/app/files dbcls/sparql-proxy
 
 
+## Plugins
+
+THIS IS AN EXPERIMENTAL FEATURE.
+
+SPARQL-proxy has a plugin system to extend its functionalities. In order to activate this feature, create `plugins.conf` file in `files` directory. The paths of the plugins to be used should be listed in this file, in the order you want to apply them. See more details in [PLUGINS.md](PLUGINS.md).
+
+This feature does not work with the query splitting mode and the passthrough mode.
+
+
 ## Relaying `X-SPARQL-` headers
 
 sparql-proxy relays HTTP headers starting with `X-SPARQL-` received from backends. This is intended to pass through `X-SPARQL-MaxRows`, which is emitted from Virtuoso.

src/plugins.ts

@@ -83,37 +83,54 @@ type Plugin = {
 
 type PluginFunc = (ctx: Context, next: PluginFunc) => Promise<Response>;
 
-export default class Plugins {
-  pluginsConfPath: string;
-  plugins: Plugin[] = [];
+async function loadPluginConf(
+  pluginsConfPath: string,
+): Promise<string[] | undefined> {
+  let text: string | undefined = undefined;
+  try {
+    text = await fs.readFile(pluginsConfPath, "utf-8");
+  } catch (e) {
+    console.log(
+      `plugin: plugin configuration ${pluginsConfPath} is not available`,
+    );
+    return undefined;
+  }
 
-  constructor(pluginsConfPath: string) {
-    this.pluginsConfPath = pluginsConfPath;
+  const paths: string[] = [];
+  for (const line of text.split(/\r?\n/)) {
+    if (line === "") continue;
+    if (line.startsWith("#")) continue;
+
+    paths.push(line);
   }
+  return paths;
+}
 
-  async loadConfig(): Promise<string[]> {
-    const text = await fs.readFile(this.pluginsConfPath, "utf-8");
-    const paths: string[] = [];
-    for (const line of text.split(/\r?\n/)) {
-      if (line === "") continue;
-      if (line.startsWith("#")) continue;
+export default class Plugins {
+  plugins: Plugin[] = [];
 
-      paths.push(line);
+  static async load(pluginsConfPath: string): Promise<Plugins | undefined> {
+    const plugins = new Plugins();
+    const pluginPaths = await loadPluginConf(pluginsConfPath);
+    if (!pluginPaths) {
+      return undefined;
     }
-    return paths;
-  }
 
-  async load() {
-    const pluginPaths = await this.loadConfig();
-    const plugins: Plugin[] = [];
     for (const dir of pluginPaths) {
-      const resolvedPath = path.resolve(dir);
-      console.log(`plugin: loading ${resolvedPath}`);
-      const plugin = await import(`${resolvedPath}/main`);
-      plugins.push(plugin);
-      console.log(`plugin: loaded ${resolvedPath}`);
+      const plugin = await plugins.importPlugin(dir);
+      plugins.plugins.push(plugin);
     }
-    this.plugins = plugins;
+
+    return plugins;
+  }
+
+  async importPlugin(pluginPath: string): Promise<Plugin> {
+    const resolvedPath = path.resolve(pluginPath);
+    console.log(`plugin: loading ${resolvedPath}`);
+    const plugin = import(`${resolvedPath}/main`);
+    console.log(`plugin: loaded ${resolvedPath}`);
+
+    return plugin;
   }
 
   async apply(

src/server.mjs

@@ -51,7 +51,6 @@ const fs = _fs.promises;
     port: Number(process.env.PORT || 3000),
     queryLogPath: process.env.QUERY_LOG_PATH,
     trustProxy: process.env.TRUST_PROXY || "false",
-    pluginsConfPath: process.env.PLUGINS,
   });
 
   const secret = `${config.adminUser}:${config.adminPassword}`;
@@ -81,11 +80,8 @@ const fs = _fs.promises;
     process.env,
   );
 
-  let plugins = null;
-  if (config.pluginsConfPath) {
-    plugins = new Plugins(config.pluginsConfPath);
-    await plugins.load();
-  } else {
+  const plugins = await Plugins.load("./files/plugins.conf");
+  if (!plugins) {
     console.log("plugin: disabled");
   }