Add Plugin loader

packages/opentelemetry-node-tracer/.gitignore

@@ -0,0 +1,2 @@
+# Dependency directories
+!test/instrumentation/node_modules

packages/opentelemetry-node-tracer/package.json

@@ -40,10 +40,13 @@
   "devDependencies": {
     "@types/mocha": "^5.2.5",
     "@types/node": "^12.6.8",
+    "@types/shimmer": "^1.0.1",
+    "@types/semver": "^6.0.1",
     "codecov": "^3.1.0",
     "gts": "^1.0.0",
     "mocha": "^6.1.0",
     "nyc": "^14.1.1",
+    "shimmer": "^1.2.0",
     "ts-mocha": "^6.0.0",
     "ts-node": "^8.0.0",
     "typescript": "^3.4.5"
@@ -53,6 +56,8 @@
     "@opentelemetry/core": "^0.0.1",
     "@opentelemetry/scope-async-hooks": "^0.0.1",
     "@opentelemetry/scope-base": "^0.0.1",
-    "@opentelemetry/types": "^0.0.1"
+    "@opentelemetry/types": "^0.0.1",
+    "require-in-the-middle": "^4.0.0",
+    "semver": "^6.2.0"
   }
 }

packages/opentelemetry-node-tracer/src/instrumentation/PluginLoader.ts

@@ -0,0 +1,144 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Logger, Plugin, Tracer } from '@opentelemetry/types';
+import * as hook from 'require-in-the-middle';
+import * as utils from './utils';
+
+// States for the Plugin Loader
+export enum HookState {
+  UNINITIALIZED,
+  ENABLED,
+  DISABLED,
+}
+
+interface PluginNames {
+  [pluginName: string]: string;
+}
+
+interface PluginConfig {
+  // TODO: Consider to add configuration options
+  [pluginName: string]: boolean;
+}
+
+/**
+ * The PluginLoader class can load instrumentation plugins that use a patch
+ * mechanism to enable automatic tracing for specific target modules.
+ */
+export class PluginLoader {
+  /** A list of loaded plugins. */
+  private _plugins: Plugin[] = [];
+  /**
+   * A field that tracks whether the require-in-the-middle hook has been loaded
+   * for the first time, as well as whether the hook body is activated or not.
+   */
+  private _hookState = HookState.UNINITIALIZED;
+
+  /** Constructs a new PluginLoader instance. */
+  constructor(readonly tracer: Tracer, readonly logger: Logger) {}
+
+  /**
+   * Loads a list of plugins. Each plugin module should implement the core
+   * {@link Plugin} interface and export an instance named as 'plugin'. This
+   * function will attach a hook to be called the first time the module is
+   * loaded.
+   * @param pluginConfig an object whose keys are plugin names and whose
+   *     boolean values indicate whether to enable the plugin.
+   */
+  load(pluginConfig: PluginConfig): PluginLoader {
+    if (this._hookState === HookState.UNINITIALIZED) {
+      const plugins = Object.keys(pluginConfig).reduce(
+        (plugins: PluginNames, moduleName: string) => {
+          if (pluginConfig[moduleName]) {
+            plugins[moduleName] = utils.defaultPackageName(moduleName);
+          }
+          return plugins;
+        },
+        {} as PluginNames
+      );
+      const modulesToHook = Object.keys(plugins);
+      // Do not hook require when no module is provided. In this case it is
+      // not necessary. With skipping this step we lower our footprint in
+      // customer applications and require-in-the-middle won't show up in CPU
+      // frames.
+      if (modulesToHook.length === 0) {
+        this._hookState = HookState.DISABLED;
+        return this;
+      }
+
+      // Enable the require hook.
+      hook(modulesToHook, (exports, name, baseDir) => {
+        if (this._hookState !== HookState.ENABLED) return exports;
+
+        const moduleName = plugins[name];
+        // Get the module version.
+        const version = utils.getPackageVersion(this.logger, baseDir as string);
+        this.logger.info(
+          `PluginLoader#load: trying loading ${name}.${version}`
+        );
+
+        // @todo (issues/132): Check if version and supportedVersions are
+        // satisfied
+        if (!version) return exports;
+
+        this.logger.debug(
+          `PluginLoader#load: applying patch to ${name}@${version} using ${moduleName} module`
+        );
+
+        // Expecting a plugin from module;
+        try {
+          const plugin: Plugin = require(moduleName).plugin;
+          this._plugins.push(plugin);
+          // Enable each supported plugin.
+          return plugin.enable(exports, this.tracer);
+        } catch (e) {
+          this.logger.error(
+            `PluginLoader#load: could not load plugin ${moduleName} of module ${name}. Error: ${e.message}`
+          );
+          return exports;
+        }
+      });
+      this._hookState = HookState.ENABLED;
+    } else if (this._hookState === HookState.DISABLED) {
+      this.logger.error(
+        'PluginLoader#load: Currently cannot re-enable plugin loader.'
+      );
+    } else {
+      this.logger.error('PluginLoader#load: Plugin loader already enabled.');
+    }
+    return this;
+  }
+
+  /** Unloads plugins. */
+  unload(): PluginLoader {
+    if (this._hookState === HookState.ENABLED) {
+      for (const plugin of this._plugins) {
+        plugin.disable();
+      }
+      this._plugins = [];
+      this._hookState = HookState.DISABLED;
+    }
+    return this;
+  }
+}
+
+/**
+ * Adds a search path for plugin modules. Intended for testing purposes only.
+ * @param searchPath The path to add.
+ */
+export function searchPathForTest(searchPath: string) {
+  module.paths.push(searchPath);
+}

packages/opentelemetry-node-tracer/src/instrumentation/constants.ts

@@ -0,0 +1,21 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/** opentelemetry scope */
+export const OPENTELEMETRY_SCOPE = '@opentelemetry';
+
+/** Default prefix for instrumentation modules */
+export const DEFAULT_PLUGIN_PACKAGE_NAME_PREFIX = 'plugin';

packages/opentelemetry-node-tracer/src/instrumentation/ext-types.d.ts

@@ -0,0 +1,28 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+declare module 'require-in-the-middle' {
+    namespace hook {
+      type Options = {
+        internals?: boolean;
+      };
+      type OnRequireFn = <T>(exports: T, name: string, basedir?: string) => T;
+    }
+    function hook(modules: string[]|null, options: hook.Options|null, onRequire: hook.OnRequireFn): void;
+    function hook(modules: string[]|null, onRequire: hook.OnRequireFn): void;
+    function hook(onRequire: hook.OnRequireFn): void;
+    export = hook;
+  }

packages/opentelemetry-node-tracer/src/instrumentation/utils.ts

@@ -0,0 +1,69 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Logger } from '@opentelemetry/types';
+import * as path from 'path';
+import * as semver from 'semver';
+import * as constants from './constants';
+
+/**
+ * Gets the default package name for a target module. The default package
+ * name uses the default scope and a default prefix.
+ * @param moduleName The module name.
+ * @returns The default name for the package.
+ */
+export function defaultPackageName(moduleName: string): string {
+  return `${constants.OPENTELEMETRY_SCOPE}/${constants.DEFAULT_PLUGIN_PACKAGE_NAME_PREFIX}-${moduleName}`;
+}
+
+/**
+ * Gets the package version.
+ * @param logger The logger to use.
+ * @param [basedir] The base directory.
+ */
+export function getPackageVersion(
+  logger: Logger,
+  basedir?: string
+): string | null {
+  if (!basedir) return null;
+
+  const pjsonPath = path.join(basedir, 'package.json');
+  try {
+    const version = require(pjsonPath).version;
+    // Attempt to parse a string as a semantic version, returning either a
+    // SemVer object or null.
+    if (!semver.parse(version)) {
+      logger.error(
+        `getPackageVersion: [${pjsonPath}|${version}] Version string could not be parsed.`
+      );
+      return null;
+    }
+    return version;
+  } catch (e) {
+    logger.error(
+      `getPackageVersion: [${pjsonPath}] An error occurred while retrieving version string. ${e.message}`
+    );
+    return null;
+  }
+}
+
+/**
+ * Adds a search path for plugin modules. Intended for testing purposes only.
+ * @param searchPath The path to add.
+ */
+export function searchPathForTest(searchPath: string) {
+  module.paths.push(searchPath);
+}