refactor: integrate logger into CMAP connection pool

Author: mbroadst

lib/cmap/connection_pool.js

@@ -2,6 +2,7 @@
 
 const Denque = require('denque');
 const EventEmitter = require('events').EventEmitter;
+const Logger = require('../core/connection/logger');
 const makeCounter = require('../utils').makeCounter;
 const MongoError = require('../core/error').MongoError;
 const Connection = require('./connection').Connection;
@@ -25,6 +26,7 @@ const ConnectionCheckedOutEvent = events.ConnectionCheckedOutEvent;
 const ConnectionCheckedInEvent = events.ConnectionCheckedInEvent;
 const ConnectionPoolClearedEvent = events.ConnectionPoolClearedEvent;
 
+const kLogger = Symbol('logger');
 const kConnections = Symbol('connections');
 const kPermits = Symbol('permits');
 const kMinPoolSizeTimer = Symbol('minPoolSizeTimer');
@@ -159,9 +161,12 @@ class ConnectionPool extends EventEmitter {
     });
 
     if (options.minSize > options.maxSize) {
-      throw new TypeError('Pool minimum size must not be greater than maxiumum pool size');
+      throw new TypeError(
+        'Connection pool minimum size must not be greater than maxiumum pool size'
+      );
     }
 
+    this[kLogger] = Logger('ConnectionPool', options);
     this[kConnections] = new Denque();
     this[kPermits] = this.options.maxPoolSize;
     this[kMinPoolSizeTimer] = undefined;
@@ -354,11 +359,6 @@ class ConnectionPool extends EventEmitter {
   get address() {
     return `${this.options.host}:${this.options.port}`;
   }
-
-  // Private Helpers
-  _propagateError() {
-    return;
-  }
 }
 
 function ensureMinPoolSize(pool) {
@@ -395,9 +395,7 @@ function createConnection(pool, callback) {
   connect(connectOptions, pool[kCancellationToken], (err, connection) => {
     if (err) {
       pool[kPermits]++;
-
-      // NOTE: integrate logger here
-      pool._propagateError(err);
+      pool[kLogger].debug(`connection attempt failed with error [${JSON.stringify(err)}]`);
       if (typeof callback === 'function') {
         callback(err);
       }