Couchbase

[PCBC-139] PHP client needs fastlz compression to be compatible with legacy memcached clients

Dependency — Tue, 11 Dec 2012 19:55:30 -0600

The existing memcached clients for PHP (pecl-memcached and memcache) both default to using fastlz compression for values >= 2000 bytes.

The couchbase client library doesn't have fastlz compression included. It doesn't provide a useful error message when it runs into this problem. Instead, it misinterprets the stored value, tries to allocate a huge block of memory and fails. The error it gives (look, e.g., in the PHP-FPM web-access.log) is:

[01-Nov-2012 20:45:49 UTC] PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 8460104323416721361 bytes) in /usr/share/nginx/html/cb.php on line 32

To reproduce, just set a value >= 2000 bytes with pecl-memcached client, and try to read it with Couchbase client. Here's a sample:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Couchbase Server PHP Test</title>
</head>
<body>

<p>
<?php

$host = "10.4.2.15";
$user = "Administrator";
$password = "password";
$bucketName = "default";
$persistConnection = false;
$cb = new Couchbase($host . ":8091",
        $user, $password, $bucketName, $persistConnection);

$mc = new Memcached('Pool-1');
if (count($mc->getServerList()) == 0) {
    // No servers, this pool needs to be configured
    $mc->addServer($host, 11211);
    //$mc->addServer("other host", 11211);
}

// Change this to 1999 and it will work
$valLength = 2000;
date_default_timezone_set('UTC');
$val = date(DateTime::RFC2822) . ' ';
$val .= str_repeat('X', $valLength - strlen($val));

$mc->set("a", $val);
echo("The value for 'a' is: ");
var_dump($cb->get("a"));

?>
</p>
</body>
</html>

The correct behavior is for the Couchbase client to ship, out of the box, compatible with existing Memcached client implementations. It should include fastlz support directly, or else clearly document how to add such support without requiring any unusual compilations or other hoops. The fastlz code is very small and portable, and hasn't changed since 2007, so it should present a minimal maintenance issue.

In addition, the PHP client documentation should clearly indicate what changes are needed in order for the client to be compatible with the other Couchbase clients (Java, .NET, etc.). Again, without requiring recompilation or extra hoops to jump through.

[PCBC-130] Remove mention of pecl-memcache and pecl-memcached from http://www.couchbase.com/develop

Tue, 16 Apr 2013 11:21:00 -0500

Is this docs or client library?

Anyway, a customer somehow missed the big "PHP 1.0" link at the top of the page and thought that he had to use pecl-memcache*. let's remove those now that we have native PHP support.

[PCBC-68] client getting NOT FOUND error for items which are present

Thu, 17 May 2012 13:03:40 -0500

A load generator test shows the client getting NOT FOUND errors when getting values that have just been set. A manual check shows the values are there.

If the server or moxi is overloaded, or there are too many connections on the host, it should return a timeout, connection error, server down, etc. But not a NOT FOUND error, which prevents the client from dealing properly with the underlying error.

Also, moxi should provide some message in its error logs if there is a connection problem.

With the test case scenario, this NOT FOUND error went away when switching to persistent connections in the new Memcached() call. So it seems some other (connection-related) error is being converted to NOT FOUND incorrectly.

[PCBC-61] Couchbase PHP vs ext/memcached compatibility

Thu, 10 May 2012 10:08:23 -0500

Here is a sample script that demonstrates the problem:

<?php

// configure Memcached to talk to bejc bucket
$mc = new Memcached();
$mc->addServer("mem1-bjb.test.vte.customer.com", 11214);
// configure Couchbase to talk to becj bucket
$cb = new Couchbase("mem1-bjb.test.vte.customer.com:8091", "", "", "bejc");

echo "Setting testKeyOne with Memcached\n";
$mc->set("testKeyOne", "testValueOne");

echo "Getting testKeyOne with Memcached\n";
var_dump($mc->get("testKeyOne"));

echo "Getting testKeyOne with Couchbase\n";
var_dump($cb->get("testKeyOne"));

echo "----------\n";

echo "Setting testKeyTwo with Couchbase\n";
$cb->set("testKeyTwo", "testValueTwo");

echo "Getting testKeyTwo with Couchbase\n";
var_dump($cb->get("testKeyTwo"));

echo "Getting testKeyTwo with Memcached\n";
var_dump($mc->get("testKeyTwo"));

?>

You need to have a Couchbase server setup with a Couchbase bucket type. Alter server names and ports/buckets to match your setup.

Save the script in a file called test.php and then run it: php test.php

The output should look something like the following:

Setting testKeyOne with Memcached
Getting testKeyOne with Memcached
string(12) "testValueOne"
Getting testKeyOne with Couchbase
int(0)
----------
Setting testKeyTwo with Couchbase
Getting testKeyTwo with Couchbase
string(12) "testValueTwo"
Getting testKeyTwo with Memcached
NULL

The script requires the Couchbase PHP library and the Memcached library to be installed.

On Debian/Ubuntu you can install the Memcached library by running:

apt-get install php5-memcached

Because of the size of our code base we need to slowly migrate to the Couchbase library so interoperability is needed. For example while we may update the actual game code to use Couchbase it might take us a while to update the CS Tools that we use to solve customer problems.