Instrument Caches

Learn how to manually instrument your code to use Sentry's Caches module.

A cache can be used to speed up data retrieval, thereby improving application performance. Because instead of getting data from a potentially slow data layer, your application will be getting data from memory (in a best case scenario). Caching can speed up read-heavy workloads for applications like Q&A portals, gaming, media sharing, and social networking.

Sentry offers a cache-monitoring dashboard for getting an overview of your application's caches.

To make it possible for Sentry to give you an overview of your cache performance, you'll need to create two spans - one indicating that something is being put into the cache, and a second one indicating that something is being fetched from the cache.

Make sure that there's a transaction running when you create the spans. If you're using a web framework like ASP.NET Core those transactions will be created for you automatically. See Performance Monitoring for more information.

For detailed information about which data can be set, see the Cache Module Developer Specification.

Follow the steps below to make sure your Cache related spans end up in Sentry correctly.

  1. Set the cache value with whatever cache library you happen to be using.
  2. Wrap the part of your application that uses the cached value with Sentry.with_child_span { |span| ... }
  3. Set op to cache.put.
  4. Set cache.item_size to an integer representing the size of the cached item.

  1. Fetch the cached value from whatever cache library you happen to be using.
  2. Wrap the part of your application that uses the cached value with Sentry.with_child_span { |span| ... }
  3. Set op to cache.get.
  4. Set cache.hit to a boolean value representing whether the value was successfully fetched from the cache or not.
  5. Set cache.item_size to an integer representing the size of the cached item.

Consider the following example service using IMemoryCache allowing you to SetInCache and GetFromCache.

Copied
using Microsoft.Extensions.Caching.Memory;

public class MyCachingService
{
    private readonly IMemoryCache _cache;

    public MyCachingService(IMemoryCache cache)
    {
        _cache = cache;
    }

    public void SetInCache(string cacheKey, object value)
    {
        var cacheSpan = SentrySdk.GetSpan()?.StartChild("cache.put");

        // Describe the cache server you are accessing
        cacheSpan?.SetExtra("network.peer.address", "cache.example.com/supercache");
        cacheSpan?.SetExtra("network.peer.port", 9000);

        // Set the key you're going to use to add to the cache
        cacheSpan?.SetExtra("cache.key", cacheKey);

        // Optional: You can also provide the cached item's size
        // cacheSpan?.SetExtra("cache.item_size", /* item size in bytes */);

        // Add an item to your cache
        _cache.Set(cacheKey, value);

        cacheSpan?.Finish();
    }

    public object? GetFromCache(string cacheKey)
    {
        var cacheSpan = SentrySdk.GetSpan()?.StartChild("cache.get");

        // Describe the cache server you are accessing
        cacheSpan?.SetExtra("network.peer.address", "cache.example.com/supercache");
        cacheSpan?.SetExtra("network.peer.port", 9000);

        // Set the key you're going to use to retrieve from the cache
        cacheSpan?.SetExtra("cache.key", cacheKey);

        // Attempt to retrieve the cached item
        if (_cache.TryGetValue(cacheKey, out var cachedValue))
        {
            // If you retrieved a value, the cache was hit
            cacheSpan?.SetExtra("cache.hit", true);

            // Optional: You can also provide the cached item's size
            // cacheSpan.SetExtra("cache.item_size", /* item size in bytes */);

            cacheSpan?.Finish();

            return cachedValue;
        }

        // If you could not retrieve a value, it was a miss
        cacheSpan?.SetExtra("cache.hit", false);
        cacheSpan?.Finish();
        return null;
    }
}

You should now have the right spans in place. Head over to the Cache dashboard to see how your cache is performing.

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