69

考虑以下是 Node.js 代码：

function My_function1(_params) {
    db.once('open', function (err){
     //Do some task 1
});
}

function My_function2(_params) {
    db.once('open', function (err){
     //Do some task 2
});
}

请参阅链接以获取最佳实践，该链接表示不要关闭任何连接

https://groups.google.com/forum/#!topic/node-mongodb-native/5cPt84TUsVg

我看到日志文件包含以下数据：

Fri Jan 18 11:00:03 Trying to start Windows service 'MongoDB'
Fri Jan 18 11:00:03 Service running
Fri Jan 18 11:00:03 [initandlisten] MongoDB starting : pid=1592 port=27017 dbpath=\data\db\ 64-bit host=AMOL-KULKARNI
Fri Jan 18 11:00:03 [initandlisten] db version v2.2.1, pdfile version 4.5
Fri Jan 18 11:00:03 [initandlisten] git version: d6...e0685521b8bc7b98fd1fab8cfeb5ae
Fri Jan 18 11:00:03 [initandlisten] build info: windows sys.getwindowsversion(major=6, minor=1, build=7601, platform=2, service_pack='Service Pack 1') BOOST_LIB_VERSION=1_49
Fri Jan 18 11:00:03 [initandlisten] options: { config: "c:\mongodb\mongod.cfg", logpath: "c:\mongodb\log\mongo.log", service: true }
Fri Jan 18 11:00:03 [initandlisten] journal dir=/data/db/journal
Fri Jan 18 11:00:03 [initandlisten] recover begin
Fri Jan 18 11:00:04 [initandlisten] recover lsn: 6624179
Fri Jan 18 11:00:04 [initandlisten] recover /data/db/journal/j._0
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:59343 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:118828 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:238138 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:835658 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:955218 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:3467218 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:3526418 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:3646154 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section seq:3705844 < lsn:6624179
Fri Jan 18 11:00:04 [initandlisten] recover skipping application of section more...
Fri Jan 18 11:00:05 [initandlisten] recover cleaning up
Fri Jan 18 11:00:05 [initandlisten] removeJournalFiles
Fri Jan 18 11:00:05 [initandlisten] recover done
Fri Jan 18 11:00:10 [initandlisten] query MYDB.system.namespaces query: { options.temp: { $in: [ true, 1 ] } } ntoreturn:0 ntoskip:0 nscanned:5 keyUpdates:0  nreturned:0 reslen:20 577ms
Fri Jan 18 11:00:10 [initandlisten] waiting for connections on port 27017
Fri Jan 18 11:00:10 [websvr] admin web console waiting for connections on port 28017
Fri Jan 18 11:01:10 [PeriodicTask::Runner] task: WriteBackManager::cleaner took: 32ms
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50076 #1 (1 connection now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50077 #2 (2 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50078 #3 (3 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50079 #4 (4 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50080 #5 (5 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50081 #6 (6 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50082 #7 (7 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50083 #8 (8 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50084 #9 (9 connections now open)
Fri Jan 18 13:36:27 [initandlisten] connection accepted from 192.168.0.1:50085 #10 (10 connections now open)
...........................................
Fri Jan 18 13:36:48 [initandlisten] connection accepted from 192.168.0.1:50092 #97 (97 connections now open)

通过打开多个连接而不是关闭它，这不会在服务器上产生开销吗？它是否在内部处理连接池？

但是在MongoDB Docs中提到“这是不使用请求池的应用程序的正常行为”

有人可以帮助我理解这一点。

4

3 回答 3

73

您使用 MongoClient 打开一次 Db 连接并在您的应用程序中重用它。如果您需要使用多个数据库，您可以使用 Db 对象上的 .db 函数来使用相同的底层连接池处理不同的数据库。保留一个池以确保单个阻塞操作不会冻结您的 node.js 应用程序。如果池中有 5 个连接，则默认大小。

http://mongodb.github.io/node-mongodb-native/driver-articles/mongoclient.html

我也忘了补充。正如另一个答案指出的那样，建立一个新的 TCP 连接在时间和内存方面都是昂贵的，这就是你重用连接的原因。此外，一个新连接也会导致在 MongoDB 上使用 Db 上的内存创建一个新线程。

于 2013-01-30T15:41:41.633 回答
24

MongoDB 将数据库连接池化以提高效率，因此在 mongodb.log 中打开许多连接并不罕见

但是，当您的应用程序完全关闭时关闭所有连接很有用。此代码最适合执行此操作。

process.on('SIGINT', function() {
  mongoose.connection.close(function () {
    console.log('Mongoose disconnected on app termination');
    process.exit(0);
  });
});
于 2015-01-13T03:23:42.077 回答
10

我不是 node.js 专家，但我认为大多数语言之间的原因是相对相同的。

建立连接是：

司机做的最重量级的事情之一。正确建立连接可能需要数百毫秒，即使在快速网络上也是如此。

（http://php.net/manual/en/mongo.connecting.pools.php）

如果那是针对 PHP 的，并且文档有点过时，那部分即使现在仍然适用，并且适用于大多数（如果不是全部）驱动程序。

每个连接也可以使用单独的线程，这会导致明显的开销。

似乎来自：

http://mongodb.github.com/node-mongodb-native/driver-articles/mongoclient.html#the-url-connection-format

该 node.js 仍然使用连接池来尝试停止建立连接的开销。当然，这不再适用于其他驱动程序，例如 PHP 驱动程序。

它打开到您的数据库服务器x的连接数量（默认为5），并在需要数据时将工作转移到空闲连接，因此重用旧连接可以避免这个可能导致这些日志的讨厌过程：

https://docs.mongodb.com/manual/faq/diagnostics/#why-does-mongodb-log-so-many-connection-accepted-events

于 2013-01-24T09:09:57.663 回答