Azure API Client

An R6 class that provides a base HTTP client for interacting with Azure APIs. This client handles authentication, request building, retry logic, logging, and error handling for Azure API requests.

Details

The api_client class is designed to be a base class for Azure service-specific clients. It provides:

• Automatic authentication using Azure credentials

• Configurable retry logic with exponential backoff

• Request and response logging

• JSON, XML, and HTML content type handling

• Standardized error handling

Public fields

.host_url

Base URL for the API

.base_req

Base httr2 request object

.provider

Credential provider R6 object

.credentials

Credentials function for authentication

.options

Request options (timeout, connecttimeout, max_tries)

.response_handler

Optional callback function to process response content

Methods

Public methods

• api_client$new()

• api_client$.fetch()

• api_client$.resp_content()

• api_client$.build_request()

• api_client$.send_request()

• api_client$.resp_body_content()

• api_client$.get_token()

• api_client$clone()

---

Method new()

Create a new API client instance

Usage

api_client$new(
  host_url,
  provider = NULL,
  credentials = NULL,
  timeout = 60L,
  connecttimeout = 30L,
  max_tries = 5L,
  response_handler = NULL
)

Arguments

host_url

A character string specifying the base URL for the API (e.g., "https://management.azure.com").

provider

An R6 credential provider object that inherits from the Credential or DefaultCredential class. If provided, the credential's req_auth method will be used for authentication. Takes precedence over credentials.

credentials

A function that adds authentication to requests. If both provider and credentials are NULL, uses default_non_auth(). The function should accept an httr2 request object and return a modified request with authentication.

timeout

An integer specifying the request timeout in seconds. Defaults to 60.

connecttimeout

An integer specifying the connection timeout in seconds. Defaults to 30.

max_tries

An integer specifying the maximum number of retry attempts for failed requests. Defaults to 5.

response_handler

An optional function to process the parsed response content. The function should accept one argument (the parsed response) and return the processed content. If NULL, uses default_response_handler() which converts data frames to data.table objects. Defaults to NULL.

Returns

A new api_client object

---

Method .fetch()

Make an HTTP request to the API

Usage

api_client$.fetch(
  path,
  ...,
  query = NULL,
  body = NULL,
  headers = NULL,
  method = "get",
  verbosity = 0L,
  content = c("body", "headers", "response", "request"),
  content_type = NULL
)

Arguments

path

A character string specifying the API endpoint path. Supports rlang::englue() syntax for variable interpolation using named arguments passed via ....

...

Named arguments used for path interpolation with rlang::englue().

query

A named list of query parameters to append to the URL.

body

Request body data. Sent as JSON in the request body. Can be a list or character string (JSON).

headers

A named list of additional HTTP headers to include in the request.

method

A character string specifying the HTTP method. One of "get", "post", "put", "patch", or "delete". Defaults to "get".

verbosity

An integer specifying the verbosity level for request debugging (passed to httr2::req_perform()). Defaults to 0.

content

A character string specifying what to return. One of:

• "body" (default): Return the parsed response body

• "headers": Return response headers

• "response": Return the full httr2 response object

• "request": Return the prepared request object without executing it

content_type

A character string specifying how to parse the response body. If NULL, uses the response's Content-Type header. Common values: "application/json", "application/xml", "text/html".

Returns

Depends on the content parameter:

• "body": Parsed response body (list, data.frame, or character)

• "headers": List of response headers

• "response": Full httr2::response() object

• "request": httr2::request() object

---

Method .resp_content()

Extract content from a response object

Usage

api_client$.resp_content(resp, content, content_type = NULL)

Arguments

resp

An httr2::response() object

content

A character string specifying what to return. One of:

• "body": Return the parsed response body

• "headers": Return response headers

• "response": Return the full httr2 response object

content_type

A character string specifying how to parse the response body. Only used when content = "body". If NULL, uses the response's Content-Type header.

Returns

Depends on the content parameter:

• "body": Parsed response body (list, data.frame, or character)

• "headers": List of response headers

• "response": Full httr2::response() object

---

Method .build_request()

Build an HTTP request object

Usage

api_client$.build_request(
  path,
  ...,
  query = NULL,
  body = NULL,
  headers = NULL,
  method = "get"
)

Arguments

path

A character string specifying the API endpoint path. Supports rlang::englue() syntax for variable interpolation using named arguments passed via ....

...

Named arguments used for path interpolation with rlang::englue().

query

A named list of query parameters to append to the URL.

body

Request body data. Sent as JSON in the request body. Can be a list or character string (JSON).

headers

A named list of additional HTTP headers to include in the request.

method

A character string specifying the HTTP method. One of "get", "post", "put", "patch", or "delete". Defaults to "get".

Returns

An httr2::request() object ready for execution

---

Method .send_request()

Perform an HTTP request and log the results

Usage

api_client$.send_request(req, verbosity)

Arguments

req

An httr2::request() object to execute

verbosity

An integer specifying the verbosity level for request debugging (passed to httr2::req_perform()). Defaults to 0.

Returns

An httr2::response() object containing the API response

---

Method .resp_body_content()

Extract and parse response content

Usage

api_client$.resp_body_content(resp, content_type = NULL)

Arguments

resp

An httr2::response() object

content_type

A character string specifying how to parse the response body. If NULL, uses the response's Content-Type header. Common values: "application/json", "application/xml", "text/html".

Returns

Parsed response body. Format depends on content type:

• JSON: List or data.frame

• XML: xml2 document

• HTML: xml2 document

• Other: Character string

---

Method .get_token()

Get authentication token from the credential provider

Usage

api_client$.get_token()

Returns

An httr2::oauth_token() object if a provider is available, otherwise returns NULL with a warning.

---

Method clone()

The objects of this class are cloneable with this method.

Usage

api_client$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

if (FALSE) { # \dontrun{
# Create a client with default credentials
client <- api_client$new(
  host_url = "https://management.azure.com"
)

# Create a client with a credential provider
cred_provider <- get_credential_provider(
  scope = "https://management.azure.com/.default"
)
client <- api_client$new(
  host_url = "https://management.azure.com",
  provider = cred_provider
)

# Create a client with custom credentials function
client <- api_client$new(
  host_url = "https://management.azure.com",
  credentials = my_credential_function,
  timeout = 120,
  max_tries = 3
)

# Create a client with custom response handler
custom_handler <- function(content) {
  # Custom processing logic - e.g., keep data frames as-is
  content
}
client <- api_client$new(
  host_url = "https://management.azure.com",
  response_handler = custom_handler
)

# Make a GET request
response <- client$.fetch(
  path = "/subscriptions/{subscription_id}/resourceGroups",
  subscription_id = "my-subscription-id",
  query = list(`api-version` = "2021-04-01"),
  method = "get"
)
} # }