Cache Settings

Information on the Cache settings section

Are you looking for the NuCache Settings?

While most cache configurations are under the Umbraco:CMS:Cache settings node, a few remain under Umbraco:CMS:NuCache. Learn more about this at the bottom of this article.

HybridCacheOptions

Umbraco's cache is implemented using Microsoft's HybridCache, which also has its own settings. For more information see the HybridCache documentation.

MaximumPayLoadBytes

One HybridCache setting of particular interest is the MaximumPayloadBytes setting. This setting specifies the maximum size of a cache entry in bytes and replaces the BTreeBlockSize setting from NuCache. The default from Microsoft is 1MB. However, this limit could quickly be reached, especially when using multiple languages or property editors like the block grid. To avoid this Umbraco overrides the setting to 100MB by default. You can also configure this manually using a composer:

using Microsoft.Extensions.Caching.Hybrid;
using Umbraco.Cms.Core.Composing;

namespace MySite.Caching;

public class ConfigureCacheComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        builder.Services.AddOptions<HybridCacheOptions>().Configure(x =>
        {
            x.MaximumPayloadBytes = 1024 * 1024 * 10; // 10MB
        });
    }
}

Seeding settings

The Seeding settings allow you to specify which content should be seeded into your cache. For more information on cache seeding see the Cache Seeding. article.

ContentTypeKeys

The ContentTypeKeys setting specifies which Document Types should be seeded into the cache. The setting is a comma-separated list of Document Type keys.

"Umbraco": {
  "CMS": {
    "Cache": {
      "ContentTypeKeys": ["e811405e-0190-4d3e-8387-7558521eec81", "419e89fb-8cff-4549-a074-9f8a30687828", "e0d71146-8205-4cf4-8236-f982b392259f"],
    }
  }
}

DocumentBreadthFirstSeedCount and MediaBreadthFirstSeedCount

The DocumentBreadthFirstSeedCount setting specifies how many documents should be seeded into the cache when doing a breadth-first traversal. MediaBreadthFirstSeedCount provides the same for media. The default value for both is 100.

"Umbraco": {
  "CMS": {
    "Cache": {
      "DocumentBreadthFirstSeedCount": 500,
      "MediaBreadthFirstSeedCount": 500
    }
  }
}

DocumentSeedBatchSize and MediaSeedBatchSize

When populating the cache on startup the content keys defined by the seeding strategy are processed in batches. The batch size for documents and media can be modified via the DocumentSeedBatchSize and MediaSeedBatchSize respectively. The default value for both is 100.

"Umbraco": {
  "CMS": {
    "Cache": {
      "DocumentSeedBatchSize": 500,
      "MediaSeedBatchSize": 500
    }
  }
}

Cache Entry settings

The Entry settings allow you to specify how long cache entries should be kept. The cache entry settings are identical for documents and media.

LocalCacheDuration

Specifies the duration for which cache entries should be kept in the local memory cache. The default value is 24 hours.

"Umbraco": {
  "CMS": {
    "Cache": {
      "Entry": {
        "Document": {
          "LocalCacheDuration": "2.00:00:00"
        },
        "Media": {
          "LocalCacheDuration": "50.00:00:00"
        }
      }
    }
  }
}

RemoteCacheDuration

Specifies the duration that cache entries should be kept in the remote cache, second level cache. This setting is only relevant if a second-level cache is configured. The default value is 1 year.

"Umbraco": {
  "CMS": {
    "Cache": {
      "Entry": {
        "Document": {
          "RemoteCacheDuration": "100.00:00:00"
        },
        "Media": {
          "RemoteCacheDuration": "150.00:00:00"
        }
      }
    }
  }
}

SeedCacheDuration

Specifies the duration for which seeded cache entries should be kept in the cache. The default value is 1 year.

"Umbraco": {
  "CMS": {
    "Cache": {
      "Entry": {
        "Document": {
          "SeedCacheDuration": "200.00:00:00"
        },
        "Media": {
          "SeedCacheDuration": "250.00:00:00"
        }
      }
    }
  }
}

MaximumLocalCacheItems

By default, the in-process (L0) published content cache is unbounded. The cache grows as content is requested. A full-tree operation can grow the cache to hold the entire tree. Examples include a Descendants query, a Delivery API crawl, sitemap generation, or a cache warm-up. On large sites this increases memory usage.

The MaximumLocalCacheItems setting limits the number of converted items kept in the L0 cache. When set, the cache becomes bounded and scan-resistant. It retains frequently requested content, such as the home page. It evicts rarely accessed content. A one-off full-tree walk can no longer grow the cache without limit.

The setting is configured separately for documents and media. The default value is null (unbounded), which preserves the previous behavior. Existing sites are unaffected unless the setting is applied.

The MaximumLocalCacheItems setting is available from Umbraco 17.6.

Installing the bounded cache package

Bounding the cache requires the opt-in Umbraco.Cms.PublishedCache.HybridCache.Bounded package. The package replaces the default L0 cache with a bounded, scan-resistant W-TinyLFU implementation.

Install the package from the folder that contains your .csproj file:

dotnet add package Umbraco.Cms.PublishedCache.HybridCache.Bounded

If you configure a maximum without installing the package, the cache stays unbounded. A warning is logged at start-up.

Configuring the maximum

With the package installed, set the maximum number of items for documents and media:

"Umbraco": {
  "CMS": {
    "Cache": {
      "Entry": {
        "Document": {
          "MaximumLocalCacheItems": 10000
        },
        "Media": {
          "MaximumLocalCacheItems": 5000
        }
      }
    }
  }
}

Keep the following in mind when configuring the maximum:

• The value is read once when the cache is constructed at start-up. Changing the value requires an application restart.
• Values below 3 are raised to 3, which is the minimum the bounded cache supports.
• Leave the setting unset on small sites. Set it on large sites that see memory pressure from full-tree scans.

You can confirm the cache stays bounded through the cache size debug logging. Once enabled, a log line reports the number of entries held in the L0 cache after browsing the site:

[20:48:46 DBG] In-memory cache size: Published content (converted, L0) = 10 entries (~46580 bytes)

Content type rebuild mode

When you save a content type with structural changes, Umbraco rebuilds the database cache for every affected content item. Structural changes include removing a property, changing a property alias, or changing the variation mode. The stale cache rows are cleared in batches before being rebuilt; the batch size can be tuned with the ContentTypeRebuildDeleteBatchSize setting.

By default, this rebuild runs during the save operation and blocks it until every content item of the affected types has been re-serialized. On sites with many content items per type, or when multiple related content types are saved in succession, the save can be slow.

ContentTypeRebuildMode

The ContentTypeRebuildMode setting controls whether the database cache rebuild runs immediately or is deferred to a background task. It accepts two values:

• Immediate (default): the database cache rebuild runs during the save operation.
• Deferred: the database cache rebuild is queued to a background task. The save returns without waiting for the rebuild to complete.

"Umbraco": {
  "CMS": {
    "Cache": {
      "ContentTypeRebuildMode": "Deferred"
    }
  }
}

When Deferred is set, the content cache is still evicted immediately during the save. The next request reads the previously serialized data from the database. Once the background rebuild completes, the content cache is evicted again, and subsequent requests pick up the fresh data. Content continues to be served throughout the rebuild without errors, but may be temporarily stale.

If multiple content types are saved in quick succession, the affected content type IDs are accumulated and processed together in a single batch. This avoids overlapping rebuild work between related types.

The same setting also controls the deferral of search re-indexing triggered by content type changes.

The ContentTypeRebuildMode setting is available from Umbraco 17.4.

Observing cache memory usage

Umbraco keeps in-memory caches whose size grows with the content tree. On large sites these caches can be a significant source of memory usage.

To help you diagnose memory pressure, Umbraco can log the approximate size of each of these caches:

• The published content and media caches.
• The document URL cache.
• The document and media navigation trees.

This observability is available from Umbraco 17.6.

A background job collects these figures every minute on all servers. For each cache it logs the approximate entry count and byte size. It also logs the process's managed heap size and working set.

The job logs at the Debug level. It does nothing unless Debug logging is enabled for its category, so there is no overhead by default.

To enable the reporting, set the log level for the job's category to Debug:

"Serilog": {
  "MinimumLevel": {
    "Default": "Information",
    "Override": {
      "Umbraco.Cms.Infrastructure.BackgroundJobs.Jobs.MemoryCacheSizeReportingJob": "Debug"
    }
  }
}

Within a minute, the cache size figures appear in the log output. For more on changing the log level for a namespace, see the Serilog settings article.

The byte figures are approximations. Use them to spot trends and attribute memory usage between caches, not as exact heap measurements.

NuCache Settings

For backward compatibility reasons, certain settings are under the Umbraco:CMS:NuCache settings node.

UsePagedSqlQuery

When UsePagedSqlQuery is set to False, the Fetch method is used instead of the QueryPaged method for rebuilding the NuCache files. This will increase performance on larger Umbraco websites with a lot of content when rebuilding the NuCache.

"Umbraco": {
  "CMS": {
    "NuCache": {
      "UsePagedSqlQuery": false
    }
   }
 }

SqlPageSize

Specifying the SqlPageSize will change the size of the paged SQL queries. The default value is 1000.

"Umbraco": {
  "CMS": {
    "NuCache": {
      "SqlPageSize": 500
    }
   }
 }

ContentTypeRebuildDeleteBatchSize

When a content type is saved with structural changes, the database cache rows for every affected content item are deleted and then rebuilt. The delete runs in batches rather than as a single unbounded DELETE.

The ContentTypeRebuildDeleteBatchSize setting controls how many content items have their cache rows deleted per batch. The default value is 2000, which is also the maximum (the effective size is capped at the SQL parameter limit). Lower it if brief lock escalation on the cmsContentNu table during a rebuild is a concern.

"Umbraco": {
  "CMS": {
    "NuCache": {
      "ContentTypeRebuildDeleteBatchSize": 1000
    }
   }
 }

The ContentTypeRebuildDeleteBatchSize setting is available from Umbraco 17.6.

NuCacheSerializerType

The NuCacheSerializerType setting allows developers to specify the serialization format for cached content.

The fastest and most compact format MessagePack is used by default.

An alternate JSON option was provided for backward compatibility for the Umbraco cache implementation used from Umbraco 8 to 14 (NuCache).

It is no longer supported with the cache implementation from Umbraco 15+ based on .NET's Hybrid cache.

The option is kept available only for a more readable format suitable for testing purposes.