feat(apm): add events for command monitoring support in core

NODE-1390

lib/connection/apm.js

@@ -0,0 +1,105 @@
+'use strict';
+
+/** Commands that we want to redact because of the sensitive nature of their contents */
+const SENSITIVE_COMMANDS = [
+  'authenticate',
+  'saslStart',
+  'saslContinue',
+  'getnonce',
+  'createUser',
+  'updateUser',
+  'copydbgetnonce',
+  'copydbsaslstart',
+  'copydb'
+];
+
+// helper methods
+function extractCommand(command) { return command.query ? command.query : command; }
+function extractCommandName(command) { return Object.keys(command)[0]; }
+function calculateDuration(started) { return Date.now() - started; }
+function generateConnectionId(pool) { return `${pool.options.host}:${pool.options.port}`; }
+function maybeRedact(commandName, result) {
+  return SENSITIVE_COMMANDS.indexOf(commandName) !== -1 ? {} : result;
+}
+
+/** An event indicating the start of a given command */
+class CommandStartedEvent {
+  /**
+   * Create a started event
+   *
+   * @param {Pool} pool the pool that originated the command
+   * @param {Object} command the command
+   */
+  constructor (pool, command) {
+    const cmd = extractCommand(command);
+    const commandName = extractCommandName(cmd);
+
+    // NOTE: remove in major revision, this is not spec behavior
+    if (SENSITIVE_COMMANDS.indexOf(commandName) !== -1) {
+      this.commandObj = {};
+      this.commandObj[commandName] = true;
+    }
+
+    Object.assign(this, {
+      command: cmd,
+      databaseName: command.ns.split('.')[0],
+      commandName: extractCommandName(cmd),
+      requestId: command.requestId,
+      connectionId: generateConnectionId(pool)
+    });
+  }
+};
+
+/** An event indicating the success of a given command */
+class CommandSucceededEvent {
+  /**
+   * Create a succeeded event
+   *
+   * @param {Pool} pool the pool that originated the command
+   * @param {Object} command the command
+   * @param {Object} reply the reply for this command from the server
+   * @param {Number} started a timestamp of when the command was first sent to calculate duration
+   */
+  constructor(pool, command, reply, started) {
+    const cmd = extractCommand(command);
+    const commandName = extractCommandName(cmd);
+
+    Object.assign(this, {
+      duration: calculateDuration(started),
+      commandName,
+      reply: maybeRedact(commandName, reply.result),
+      requestId: command.requestId,
+      connectionId: generateConnectionId(pool)
+    });
+  }
+};
+
+/** An event indicating the failure of a given command */
+class CommandFailedEvent {
+  /**
+   * Create a failure event
+   *
+   * @param {Pool} pool the pool that originated the command
+   * @param {Object} command the command
+   * @param {MongoError|Object} error the generated error or a server error response
+   * @param {Number} started a timestamp of when the command was first sent to calculate duration
+   */
+  constructor(pool, command, error, started) {
+    const cmd = extractCommand(command);
+    const commandName = extractCommandName(cmd);
+
+    Object.assign(this, {
+      duration: calculateDuration(started),
+      commandName,
+      failure: maybeRedact(commandName, error),
+      requestId: command.requestId,
+      connectionId: generateConnectionId(pool)
+    });
+  }
+};
+
+module.exports = {
+  CommandStartedEvent,
+  CommandSucceededEvent,
+  CommandFailedEvent
+};