Persistent/keepalive HTTP with the PHP Curl library?

user_82769 0
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I'm using a simple PHP library to add documents to a SOLR index, via HTTP.

There are 3 servers involved, currently:

  1. The PHP box running the indexing job
  2. A database box holding the data being indexed
  3. The solr box.

At 80 documents/sec (out of 1 million docs), I'm noticing an unusually high interrupt rate on the network interfaces on the PHP and solr boxes (2000/sec; what's more, the graphs are nearly identical -- when the interrupt rate on the PHP box spikes, it also spikes on the Solr box), but much less so on the database box (300/sec). I imagine this is simply because I open and reuse a single connection to the database server, but every single Solr request is currently opening a new HTTP connection via cURL, thanks to the way the Solr client library is written.

So, my question is:

  1. Can cURL be made to open a keepalive session?
  2. What does it take to reuse a connection? -- is it as simple as reusing the cURL handle resource?
  3. Do I need to set any special cURL options? (e.g. force HTTP 1.1?)
  4. Are there any gotchas with cURL keepalive connections? This script runs for hours at a time; will I be able to use a single connection, or will I need to periodically reconnect?
keep-alive libcurl curl http php
4 Answers

cURL PHP documentation (curl_setopt) says:

CURLOPT_FORBID_REUSE - TRUE to force the connection to explicitly close when it has finished processing, and not be pooled for reuse.

So:

  1. Yes, actually it should re-use connections by default, as long as you re-use the cURL handle.
  2. by default, cURL handles persistent connections by itself; should you need some special headers, check CURLOPT_HTTPHEADER
  3. the server may send a keep-alive timeout (with default Apache install, it is 15 seconds or 100 requests, whichever comes first) - but cURL will just open another connection when that happens.
Piskvor_197460

Curl sends the keep-alive header by default, but:

  1. create a context using curl_init() without any parameters.
  2. store the context in a scope where it will survive (not a local var)
  3. use CURLOPT_URL option to pass the url to the context
  4. execute the request using curl_exec()
  5. don't close the connection with curl_close()

very basic example:

function get($url) {
    global $context;
    curl_setopt($context, CURLOPT_URL, $url);
    return curl_exec($context);
}

$context = curl_init();
//multiple calls to get() here
curl_close($context);
user_13241910

If you don't care about the response from the request, you can do them asynchronously, but you run the risk of overloading your SOLR index. I doubt it though, SOLR is pretty damn quick.

Asynchronous PHP calls?

UltimateBrent_106800
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