PHP Redis: Get Current Memory Usage (Detailed Guide w/ Code Examples)

Use Case(s)

In PHP Redis, getting the current memory usage is important for monitoring and debugging. This can be used to keep track of how much memory your Redis server is using at any given moment, and determine if there are any memory leaks.

Code Examples

Example 1: Get the memory usage

<?php
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$info = $redis->info();
print_r($info['used_memory']);
?>

This code connects to a Redis server and calls info(), which returns various information about the Redis server including its current memory usage. The memory usage is then printed to the console.

Best Practices

While checking memory usage in Redis, always be aware that the 'used_memory' field only shows the amount of memory taken by Redis itself and does not include additional overheads. Also, regularly check the memory usage, especially after significant write operations or deletions.

Common Mistakes

One common mistake when interpreting the result of info() is overlooking that 'used_memory' refers to the total amount of bytes allocated by Redis using its allocator (either standard libc, jemalloc, or an alternative). It does not account for other auxiliary processes and overheads.

FAQs

Q: Why is the 'used_memory' value significantly higher than my data size?

A: This could be due to either memory fragmentation or Redis maintaining extra copies of certain data structures for faster performance.