Hybrid Cache - DefaultJsonSerializer Error

warren · October 16, 2025, 2:04pm

Fixed

For anyone following along the FATAL log error message bug has been fixed in 16.3.0 with this PR

github.com/umbraco/Umbraco-CMS

Hybrid cache: Check for `ContentCacheNode` instead of object on exists for hybrid cache to ensure correct deserialization (closes #20352)

main ← v16/bugfix/fix-deserialization-issue-on-exists-check-with-l2-hybrid-cache

opened 02:27PM - 06 Oct 25 UTC

AndyButland

+13 -12

### Prerequisites - [X] I have added steps to test this contribution in the d…escription below Fixes https://github.com/umbraco/Umbraco-CMS/issues/20352 caused by a regression introduced by https://github.com/umbraco/Umbraco-CMS/pull/19890. ### Description Although the reported issue related to Redis, this is visible with any L2 cache other than a memory cache where deserialization is required. The problem comes about because we are using `object` to verify the existence of something in the cache, rather than the actual object `ContentCacheNode` we always store, which has configured serialization rules. As such the deserialization is using the default JSON serializer, which fails as we aren't stored cached values as JSON. ### Testing Set up SQL L2 cache, which if running from source, is done by: - Add the following to `Directory.Packages.props`: ``` <ItemGroup> <PackageVersion Include="Microsoft.Extensions.Caching.SqlServer" Version="9.0.9" /> </ItemGroup> ``` - Add the following to `Umbraco.Web.UI.csproj`: ``` <ItemGroup> <PackageReference Include="Microsoft.Extensions.Caching.SqlServer" /> </ItemGroup> ``` - Add the following to `Program.cs`, just before `WebApplication app = builder.Build();`: ``` builder.Services.AddDistributedSqlServerCache(options => { options.ConnectionString = builder.Configuration.GetConnectionString("SqlDistributedCache"); options.SchemaName = "dbo"; options.TableName = "TestCache"; }); ``` - Create a SQL Server database - Populate the database with: ``` dotnet tool install --global dotnet-sql-cache dotnet sql-cache create "Server=.\SQLEXPRESS;Database=MyDatabase;Integrated Security=true;TrustServerCertificate=true;" dbo TestCache ``` - Add the following connection string to `appSettings.json`: ``` "SqlDistributedCache": "Server=.\\SQLEXPRESS;Database=UmbracoCms16HybridCache;Integrated Security=true;TrustServerCertificate=true;" ``` Now verify the issue resolution with: - Start up Umbraco using code from `main`. The first time it'll be fine, as the table is empty and will be populated. - Verify via `select * from TestCache` - Stop and start Umbraco again. You should now hit the error: ``` An error occurred starting the application System.AggregateException: One or more errors occurred. (One or more errors occurred. ('0x92' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.)) ``` - Check out the code in this branch and empty the table with `truncate table TestCache` - Repeat starting up Umbraco twice. This time there should be no error on the second restart.

Redis Insights

I am not 100% sure if I am able to ever truly view/read the contents in Redis Insight desktop tool in a human readable way.

If anyone knows if we should or not that would be good to know