Hosting with .NET Aspire

SQLite is a file, so Aspire has nothing to start for Fisher: the AppHost's job is to say which file and hand that to the service. Two routes.

Fisher.Aspire.Hosting

dotnet add package Fisher.Aspire.Hosting

In the AppHost:

var orders = builder.AddFisher("orders", "/data/orders.db"); // path optional: defaults to ./orders.db

builder.AddProject<Projects.Api>("api")
    .WithReference(orders)   // ConnectionStrings__orders = "Data Source=/data/orders.db"
    .WithVolume(orders);     // FISHER_DATA_DIRECTORY = /data

In the service, the connection string is an ordinary SQLite one:

builder.Services.AddFisher(builder.Configuration.GetConnectionString("orders")!);

WithVolume sets FISHER_DATA_DIRECTORY on a project or container so the service can find the directory a mounted volume provides. It does not mount anything itself.

Community Toolkit AddSqliteConnection

If the AppHost already uses the Aspire Community Toolkit's SQLite integration (AddSqlite), the connection string it hands a project works with AddFisher(connectionString). CommunityToolkit.Aspire.Hosting.Sqlite 13.6.1 produces Data Source={path};Cache=Shared;Mode=ReadWriteCreate, which Microsoft.Data.Sqlite opens as an ordinary file. Fisher then applies its own schema, journal mode and PRAGMAs through its own data source, so the file still runs in WAL, and concurrent writers commit with the async daemon reading beside them under the shared cache. community_toolkit_connection_string in Fisher's suite pins that string; another toolkit version could produce a different one.

On the service side you do not need the toolkit's client package (AddSqliteConnection): read the connection string from configuration and pass it to AddFisher, as above.

OpenTelemetry

Fisher emits an ActivitySource and a Meter both named Fisher. Register them with the service defaults' OpenTelemetry setup:

builder.Services.AddOpenTelemetry()
    .WithTracing(t => t.AddSource("Fisher"))
    .WithMetrics(m => m.AddMeter("Fisher"));

Metric instruments are opt-in through StoreOptions.OpenTelemetry; see Diagnostics.

Health check

With Fisher.AspNetCore, AddHealthChecks().AddFisherHighWaterHealthCheck() reports a stuck async daemon, which the Aspire dashboard shows on the service's tile.