php and persistent HTTP connections

Question

There is any way you can use HTTP persistent connections between requests ? I don't see the CURL extensions having a way to create a pool of connections that's used by all requests as there are in other extensions for mysql, redis, pg.

From what I see you can use persistent http connections only inside the same request.

Silviu

score 3 · Accepted Answer · answered Jan 13 '17 at 21:24

The pecl_http extension for PHP uses libcurl and allows you to open a persistent TCP connection that can be reused:

$client = new http\Client('curl', $persistentHandleID); 
$request = new http\Client\Request('GET', 'http://example.com/');
$client->enqueue($request);
$client->send();
$response = $client->getResponse($request);

If another $client running on the same PHP process (possibly during a different PHP request) accesses the same host and shares the same $persistentHandleID, it will send its HTTP requests over the same TCP connection as before.

The TCP connection will be kept alive until the PHP module is shut down or until the $client sends Connection: Close or forbids further use of the connection:

$client->setOptions(['forbid_reuse' => true, … ]);

You might wanna take a look at this excellent article: http://technosophos.com/2012/06/18/connection-sharing-curl-php-how-re-use-http-connections-knock-70-rest-network-time.html — Omid Ariyan, Apr 03 '18 at 08:25

score 2 · Answer 2 · answered Jan 12 '17 at 22:48

In HTTP there is the concept of keep-alive and pipelining. Keep-Alive allows one TCP connection to be used across multiple HTTP requests and responses. This allows a browser to load a web page with all its resources (e.g. images, scripts, etc.) on one TCP connection, which avoids the connection setup and tear down overhead. CURL uses this by default, appending Connection: keep-alive to the header. The server is configured for max requests and how long the connection will remain open. But it still acts in a request- response mode.

With Pipelining multiple requests can be made prior to receiving a response. Pipelining is not widely implemented and to work both the client and server must implement it. To use in CURL you must find a library (there are some out there) which implements it for you client, and again the server must also utilize it.

If you are unsure if your CURL app is sending the keep-alive header then use an http proxy or packet sniffer to inspect your traffic.

With HTTP/1.1 persistent connections are the default and no `Connection:` header is needed for that. All a PHP program needs to do is to reuse the same curl handle when doing subsequent requests. — Daniel Stenberg, Jan 12 '17 at 22:53
my question was : There is any way you can use HTTP persistent connections between requests and also in the final post I worte: From what I see you can use persistent http connections only inside the same request. Because of the php scripts life-cycle I don't see how you can use a pool of connections. — silviu, Jan 13 '17 at 06:08

php and persistent HTTP connections

2 Answers2