Confirming fast performance running Apache and MongoDB (even a replicaSet secondary, with distant primary over WAN) on same box, communicating via unix domain socket.
$Mongo = new \MongoClient(
'mongodb:///tmp/mongodb-27017.sock'
, array(
'replicaSet' => 'rs1'
, 'timeout' => 300000
)
);
$Mdb = $Mongo->DB; // create or open DB
$Mdb->setReadPreference( \MongoClient::RP_NEAREST );
"Postgres core developer Bruce Momjian has blogged about this topic. Momjian states, "Unix-domain socket communication is measurably faster." He measured query network performance showing that the local domain socket was 33% faster than using the TCP/IP stack."
http://stackoverflow.com/questions/257433/postgresql-unix-domain-sockets-vs-tcp-sockets
Excerpt: IP sockets over localhost are basically looped back network on-the-wireIP. There is intentionally “no special knowledge” of the fact that the connection is to the same system, so no effort is made to bypass the normal IP stack mechanisms for performance reasons. For example, transmission over TCP will always involve two context switches to get to the remote socket, as you have to switch through the netisr, which occurs following the “loopback” of the packet through the synthetic loopback interface. Likewise, you get all the overhead of ACKs, TCP flow control, encapsulation/decapsulation, etc. Routing will be performed in order to decide if the packets go to the localhost. Large sends will have to be broken down into MTU-size datagrams, which also adds overhead for large writes. It’s really TCP, it just goes over a loopback interface by virtue of a special address, or discovering that the address requested is served locally rather than over an ethernet (etc).
UNIX domain sockets have explicit knowledge that they’re executing on the same system. They avoid the extra context switch through the netisr, and a sending thread will write the stream or datagrams directly into the receiving socket buffer. No checksums are calculated, no headers are inserted, no routing is performed, etc. Because they have access to the remote socket buffer, they can also directly provide feedback to the sender when it is filling, or more importantly, emptying, rather than having the added overhead of explicit acknowledgement and window changes. The one piece of functionality that UNIX domain sockets don’t provide that TCP does is out-of-band data. In practice, this is an issue for almost noone.
http://osnet.cs.binghamton.edu/publications/TR-20070820.pdf
Excerpt: It was hypothesized that pipes would have the highest throughtput due to its limited functionality, since it is half-duplex, but this was not true. For almost all of the data sizes transferred, Unix domain sockets performed better than both TCP sockets and pipes, as can be seen in Figure 1 below. Figure 1 shows the transfer rates for the IPC mechanisms, but it should be noted that they do not represent the speeds obtained by all of the test machines. The transfer rates are consistent across the machines with similar hardware configurations though. On some machines, Unix domain sockets reached transfer rates as high as 1500 MB/s.
http://bhavin.directi.com/unix-domain-sockets-vs-tcp-sockets/
Unix Domain Socket支持
MongoDB 服务程序内置支持通过 Unix Sockets 链接，并且会在启动时建立socket，默认位置在 /tmp/mongodb-<port>.sock..
要通过socket链接，需要在连接字符串中指定socket路径，如：
<?php
$m = new MongoClient("mongodb:///tmp/mongo-27017.sock");
?>
如果要在通过socket的链接中对数据库进行认证（如上文所述），你需要指定一个端口号
0 让链接字符串解析时可以找到 socket路径 的结尾。另外，你可以在链接的时候使用options参数。
<?php
$m = new MongoClient("mongodb://username:password@/tmp/mongo-27017.sock:0/foo");
?>
更新日志
| 版本 | 说明 |
|---|---|
| 1.0.9 | 添加 Unix Sockets 的支持。 |
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User Contributed Notes 3 notes
East Ghost Com ¶
11 years ago
mike at eastghost dot com ¶
11 years ago
We've enjoyed a 100x - 200x speed boost, just changing from TCP connection to unix domain socket. Page loads went from 1,400 ms down to 7 ms instantly.
ere dot maijala at helsinki dot fi ¶
11 years ago
In my case (CentOS 6.4, PHP 5.3.3, MongoDB 2.4.5, PHP Mongo driver 1.4.2, all on the same system under VMWare, mixed updates, inserts and finds) unix domain sockets seem to work more than ten times faster than a TCP/IP connection to localhost.
