# Reference manual

## Local FaaSr Execution

This package helps users simulate the entire FaaSr workflow without the need for interacting without Cloud-related interactions. This give the user the opportunity to verify that their workflow are behaving correctly before moving into actual cloud execution.

This local execution requires the FaaSr JSON workflow to match the schema with valid functions and ActionList. However, credentials for Cloud Platforms and S3 Storage or ActionContainers aren’t needed to be specified and won’t be used.

## Getting Started

### File Structure Setup

To use FaaSr, you need to organize your project files as follows:

    your-project/
    ├── workflow.json              # Your FaaSr workflow configuration (you will be passing this path)
    ├── faasr_data/                # Created automatically by faasr_test()
    │   ├── functions/             # (Optional) User R functions
    │   ├── files/                 # Simulated S3 storage
    │   ├── logs/                  # Log files
    │   └── temp/                  # Temporary execution files
    └── my_functions.R             # (Optional) Your R functions

Key Components:

1. Workflow JSON file: Your FaaSr workflow configuration (can be anywhere; you pass the path to `faasr_test()`)

2. R Functions: Your workflow functions can be stored in several locations:

   - In the package’s `inst/extdata/functions/` directory (for package development)
   - In `faasr_data/functions/` in your working directory
   - As standalone R files that you source before calling `faasr_test()`

3. faasr_data folder: Automatically created by `faasr_test()` to simulate cloud infrastructure:

   - `files/` - Simulates S3 bucket storage for file operations
   - `logs/` - Stores execution logs from `faasr_log()` calls
   - `temp/` - Temporary workspace for function execution

### Creating a Workflow Configuration

The workflow JSON configuration file is described by the FaaSr JSON schema.

Recommended approach: Use the FaaSr workflow builder to create and manage your workflow configuration files with a visual interface.

### faasr_test

Usage: `faasr_test(json_path)`

`json_path` is a required argument and specifies the path of a FaaSr workflow configuration file

This is the only function that you need to call in order to run this local test. It loads the JSON-formatted workflow configuration file from the path specified by `json_path` and execute the functions in the order specified in the workflow.

## FaaSr APIs

These are the FaaSr functions that users add to their R functions. They are used to read and write from/to S3 buckets and to generate logs for debugging. This package will simulate these behaviors using `faasr_data` folder as a bucket in S3 Storage.

### faasr_put_file

Usage: `faasr_put_file(server_name = NULL, local_folder = ".", local_file, remote_folder = "", remote_file)`

Uploads a file from the local filesystem to the local FaaSr storage (simulating S3 bucket upload).

Parameters: - `server_name`: String specifying the server name (ignored in local implementation) - `local_folder`: String path to the local folder containing the file to upload (default: “.”) - `local_file`: String name of the local file to upload (required) - `remote_folder`: String path to the remote folder where the file will be stored (default: ““) - `remote_file`: String name for the file in remote storage (required)

Example:

    faasr_put_file(local_file="output.csv", remote_folder="myfolder", remote_file="myoutput.csv")

### faasr_get_file

Usage: `faasr_get_file(server_name = NULL, remote_folder = "", remote_file, local_folder = ".", local_file)`

Downloads a file from the local FaaSr storage to the local filesystem (simulating S3 bucket download).

Parameters: - `server_name`: String specifying the server name (ignored in local implementation) - `remote_folder`: String path to the remote folder containing the file to download (default: ““) - `remote_file`: String name of the remote file to download (required) - `local_folder`: String path to the local folder where the file will be saved (default:”.”) - `local_file`: String name for the file in local storage (required)

Example:

    faasr_get_file(remote_folder="myfolder", remote_file="myinput1.csv", local_file="input1.csv")
    faasr_get_file(server_name="My_Minio_Bucket", remote_file="myinput2.csv", local_file="input2.csv")

### faasr_delete_file

Usage: `faasr_delete_file(server_name = NULL, remote_folder = "", remote_file)`

Deletes a file from the local FaaSr storage (simulating S3 bucket file deletion).

Parameters: - `server_name`: Character string specifying the server name (ignored in local implementation) - `remote_folder`: Character string path to the remote folder containing the file to delete (default: ““) - `remote_file`: Character string name of the remote file to delete (required)

Example:

    faasr_delete_file(remote_folder="myfolder", remote_file="myoutput.csv")
    faasr_delete_file(server_name="My_Minio_Bucket", remote_file="myoutput.csv")

### faasr_get_folder_list

Usage: `faasr_get_folder_list(server_name = NULL, faasr_prefix = "")`

Lists all files in the local FaaSr storage, optionally filtered by a prefix (simulating S3 bucket listing).

Parameters: - `server_name`: Character string specifying the server name (ignored in local implementation) - `faasr_prefix`: Character string prefix to filter file names (optional, default: ““)

Returns: Character vector of file names matching the criteria

Example:

    mylist1 <- faasr_get_folder_list(server_name="My_Minio_Bucket", faasr_prefix="myfolder")
    mylist2 <- faasr_get_folder_list(server_name="My_Minio_Bucket", faasr_prefix="myfolder/mysubfolder")

### faasr_log

Usage: `faasr_log(log_message)`

Appends a log message with timestamp to the local FaaSr log file. This is useful for debugging and tracking workflow execution.

Parameters: - `log_message`: Character string message to log (required)

Example:

    log_msg <- paste0('Function compute_sum finished; output written to ', folder, '/', output, ' in default S3 bucket')
    faasr_log(log_msg)

### faasr_rank

Usage: `faasr_rank()`

Returns the current rank information for the executing function in a parallel workflow. This is useful when functions are executed in parallel and need to know their position in the execution order.

Returns: List containing `rank` and `max_rank`, or empty list if no rank information is available

Example:

    # Get current rank information
    rank_info <- faasr_rank()
    if (length(rank_info) > 0) {
      cat("Current rank:", rank_info$rank, "of", rank_info$max_rank, "\n")
    }

### faasr_invocation_id

Usage: `faasr_invocation_id()`

Returns the invocation ID for the current workflow execution. This unique identifier can be used to track and correlate logs and outputs from a specific workflow run.

Returns: Character string invocation ID, or NULL if not available

Example:

    # Get current invocation ID
    inv_id <- faasr_invocation_id()
    if (!is.null(inv_id)) {
      cat("Invocation ID:", inv_id, "\n")
    }