Question: What are the error codes in Memcached?


Memcached is a popular distributed caching system that is used to speed up web applications by caching data in memory. While using Memcached, you may come across various error codes, which can help you diagnose and fix issues with your cache.

Here are some common error codes you may encounter while working with Memcached:

  1. ERR_NOT_FOUND: This error occurs when you try to retrieve an item from the cache that does not exist.
  2. ERR_EXISTS: This error occurs when you try to store an item in the cache that already exists.
  3. ERR_CACHE_MISS: This error occurs when Memcached is unable to retrieve an item from the cache due to a cache miss.
  4. ERR_BAD_COMMAND: This error occurs when you send an invalid command to the Memcached server.
  5. ERR_SERVER: This error occurs when there is an issue with the Memcached server, such as a network outage or hardware failure.
  6. ERR_CLIENT: This error occurs when there is an issue with the client connecting to the Memcached server, such as authentication failure or incorrect configuration parameters.

In addition to these error codes, Memcached also provides detailed error messages that can provide additional information about the nature of the error. For example, if you receive an ERR_NOT_FOUND error, the error message may indicate which key was not found in the cache.

Here's an example showing how to handle errors in PHP when working with Memcached:

$memcached = new Memcached();
$memcached->addServer('localhost', 11211);

$value = $memcached->get('my_key');
if ($memcached->getResultCode() == Memcached::RES_NOTFOUND) {
    echo 'Value not found in cache';
} elseif ($memcached->getResultCode() == Memcached::RES_SUCCESS) {
    echo 'Value retrieved from cache: ' . $value;
} else {
    echo 'Error retrieving value from cache: ' . $memcached->getResultMessage();

In this example, we use the getResultCode() method to check the result code of the previous Memcached operation. We then use an if-elseif-else statement to handle the various possible outcomes. Finally, we use the getResultMessage() method to retrieve the error message in case of an error.

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