R/faasr_log.R

In FaaSr: FaaS (Function as a Service) Package

#' @name faasr_log
#' @title faasr_log
#' @description 
#' Helper function to append to the log file residing in an S3 bucket
#' the name of the S3 server is implicit from the validated JSON payload, key LoggingServer
#' the log file is a concatenation of folder "logs" and file name "faasr_log_" + InvocationID + ".txt"
#' @param faasr list with parsed and validated Payload
#' @param log_message string message to be appended to the log
#' @return return nothing / leave the log to the bucket
#' @importFrom "paws.storage" "s3"
#' @importFrom "utils" "write.table"
#' @export
#' @examples
#' # This function can be run only in the container
#' if (interactive()){
#' log_message <- "test message"
#' faasr_log(log_message)
#' }

globalVariables(".faasr")

faasr_log <- function(log_message) {

  # Extract name of logging server
  if (is.null(.faasr$LoggingDataStore)){
    log_server_name = .faasr$DefaultDataStore
  } else {
    log_server_name = .faasr$LoggingDataStore
  }
  # Validate that server_name exists, otherwise abort
  if (log_server_name %in% names(.faasr$DataStores)) {
    NULL
   } else {
     err_msg <- paste0('{\"faasr_log\":\"Invalid logging server name: ',log_server_name,'\"}', "\n")
     message(err_msg)
     stop()
   }

  log_server <- .faasr$DataStores[[log_server_name]]

  s3<-paws.storage::s3(
    config=list(
	  credentials=list(
	    creds=list(
		  access_key_id=log_server$AccessKey,
		  secret_access_key=log_server$SecretKey
		)
	  ),
	  endpoint=log_server$Endpoint,
	  region=log_server$Region
	)
  )

  # set file name to be "faasr_log_" + faasr$InvocationID + faasr$FunctionInvoke + ".txt"
  log_folder <- paste0(.faasr$FaaSrLog, "/", .faasr$InvocationID)
  log_file <- paste0(log_folder, "/", .faasr$FunctionInvoke,".txt")
  if (!dir.exists(log_folder)){dir.create(log_folder, recursive=TRUE)}

  check_log_file <- s3$list_objects_v2(Bucket=log_server$Bucket, Prefix=log_file)
  if (length(check_log_file$Contents) != 0) {
	  if (file.exists(log_file)) {
	    file.remove(log_file)
	  }
	  s3$download_file(Bucket=log_server$Bucket, Key=log_file, Filename=log_file)
  }

  # append message to the local file then upload
  logs <- log_message
  write.table(logs, log_file, col.names=FALSE, row.names = FALSE, append=TRUE, quote=FALSE)
  s3$put_object(Body=log_file, Key=log_file, Bucket=log_server$Bucket)
}