Invoke a published Fabric user data function — fabric_function

Usage

fabric_function_invoke(
  function_url,
  parameters = list(),
  timeout = 110,
  idempotent = FALSE,
  max_response_bytes = .fabric_function_response_limit,
  tenant_id = Sys.getenv("FABRICQUERYR_TENANT_ID"),
  client_id = Sys.getenv("FABRICQUERYR_CLIENT_ID", unset =
    "04b07795-8ddb-461a-bbee-02f9e1bf7b46"),
  token = NULL,
  auth_args = list(),
  audience = NULL
)

Arguments

function_url: Complete public URL copied from the published function's properties in Fabric. A discovered UserDataFunction item is not sufficient because the item API does not return the public function URL.
parameters: Named list, data frame, or named atomic vector serialized as the JSON object supplied to the function. Use list() for a function with no parameters.
timeout: Positive client request timeout in seconds. Fabric currently limits execution through a public function endpoint to 100 seconds.
idempotent: Logical. Permit bounded retries after transient failures. Keep FALSE for functions whose side effects cannot safely be repeated.
max_response_bytes: Positive whole-number client limit for the complete response body. The default is 32 MiB, slightly above Fabric's documented 30 MB function-output limit.
tenant_id: Microsoft Entra tenant ID. Defaults to FABRICQUERYR_TENANT_ID.
client_id: Microsoft Entra application/client ID. Defaults to FABRICQUERYR_CLIENT_ID, with the Azure CLI application ID as fallback.
token: Optional access token or token-provider function. Leave NULL to let 'fabricQueryR' use its normal sign-in flow for a Microsoft Fabric host. A custom function_url requires an explicitly supplied token or provider so an automatically acquired Fabric credential is not forwarded to another host.
auth_args: Additional sign-in options passed to AzureAuth::get_azure_token().
audience: OAuth audience/scope passed to the credential. NULL selects UserDataFunction.Execute.All for delegated sign-in or the Power BI .default audience for client credentials. To use Microsoft's broader alternative, pass "https://analysis.windows.net/powerbi/api/Item.Execute.All" explicitly.

Value

A fabric_function_result list with function_name, invocation_id, status, output, errors, http_status, and response. Function output is returned unchanged because field names such as token can be legitimate domain data. The rest of response is redacted and retains unknown future fields. Inspect status and errors; receiving a result does not by itself mean the function succeeded.

Details

Calls the public REST endpoint for one published Microsoft Fabric user data function and returns the service's synchronous execution result. Function definition, publication, and deployment are intentionally outside this helper's scope.

This invocation API is experimental because its request and response handling is covered by offline tests, but the package cannot currently maintain repeatable end-to-end coverage against published functions. The package's development sandbox uses a service principal, while Fabric's User Data Function create, update-definition, and delete APIs currently support delegated user identities only. The sandbox therefore cannot provision and maintain the published public-function fixtures needed for that coverage.

Before you invoke

Publish the user data functions item, switch it to Run only mode, enable Public access for the function, and copy its Public URL from the Fabric portal. Pass that complete URL to function_url; item discovery does not currently expose enough information to derive a public function URL safely.

Parameter names and values must match the published Python signature. Fabric supports JSON strings, ISO 8601 datetime strings, booleans, numbers, arrays, and objects as inputs. The top-level parameters object therefore needs unique, non-empty camelCase names without underscores. Python keywords and Fabric's reserved req, context, and reqInvocationId names are rejected before a request is sent. A named atomic vector is converted to a named list; use I() around a one-element value when it must remain a JSON array.

Permissions and authentication

Delegated authentication defaults to the narrower Power BI permission UserDataFunction.Execute.All. Microsoft also accepts the broader Item.Execute.All permission; use it only when the app registration grants that scope, and pass its full scope URL explicitly through audience. Either delegated scope still requires Execute permission on the user data functions item. Service-to-service callers can use an application credential with the Power BI .default audience and the required tenant and item access.

Application authentication for the public invocation endpoint is distinct from authentication used by connections inside the function. Microsoft currently does not support using a service principal through connections managed by user data functions to access Fabric items or data sources. A service principal can therefore invoke a compatible function while a function that relies on an unsupported managed connection can still fail.

The function URL is a credential boundary. Tokens are sent to the explicitly supplied HTTPS endpoint. URLs containing credentials, query parameters, fragments, or nonstandard ports are rejected. HTTPS and route validation do not prove hostname ownership or token audience. Use a custom host only when your organization controls it, with a token or provider issued for that host's intended audience.

Results, retries, and limits

Fabric reports Succeeded, BadRequest, Failed, Timeout, and ResponseTooLarge through one response envelope. Valid envelopes remain inspectable as fabric_function_result objects even when Fabric uses a non-success HTTP status. Authentication, authorization, throttling, and malformed service responses continue to raise the package's typed HTTP or response errors. The documentation describes an error name, while current responses can use errorCode; errors adds name as an alias when needed and response retains the original service shape.

Invocations are not retried by default because functions can have arbitrary side effects. Set idempotent = TRUE only when repeating the function is safe; this enables the package's bounded retries for transport failures, throttling, and transient HTTP responses.

Fabric limits public-endpoint execution to 100 seconds, request parameters to 4 MB, and a function's return value to 30 MB. The default 110-second client timeout allows the service timeout response to arrive. The 32 MiB client response cap leaves room for Fabric's envelope around a 30 MB output. Secret-named fields and bearer-token text are redacted recursively from errors, response metadata, and conditions. Function output is domain data and is returned unchanged, even when it contains secret-like field names.

References

Invoke user data functions from a Python application

Fabric user data functions service limits

Fabric user data function programming model

Examples

if (FALSE) { # \dontrun{
# Discover the user data functions item that owns the published function
workspace <- fabric_workspaces()[[1L]]
function_item <- fabric_user_data_functions(workspace)[[1L]]
function_item$displayName

# Discovery cannot expose a function URL yet. Copy the published function's
# complete Invoke URL from this item's Run-only settings into this variable
function_url <- Sys.getenv("FABRIC_FUNCTION_URL")

# Parameter names must match the published Python function signature
result <- fabric_function_invoke(
  function_url,
  parameters = list(
    customerName = "Ada",
    order = list(id = 42L, lines = I(c("A", "B")))
  )
)

# Inspect the output and any function-level errors returned by Fabric
result$status
result$output
result$errors
} # }