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FIRECLOUD | Doc #12221 | Error message: File is larger than 1000000 Bytes…

Error message: File is larger than 1000000 Bytes…
Solutions to Problems | Created 2018-06-15 | Last updated 2018-06-15

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You’ve likely used one of the read_X functions in your WDL and have surpassed the default limits set in FireCloud’s Cromwell instance. In practice when Cromwell starts reading a file and surpasses the size limit, Cromwell will immediately stop downloading and fail the workflow giving you this error message. If you want to know why these limits were introduced, read this blog post (link coming soon).


  • read_lines: = 1MB
  • read_json = 1MB
  • read_tsv = 1MB
  • read_object = 1MB
  • read_boolean = 7 bytes
  • read_int = 19 bytes
  • read_float = 50 bytes
  • read_string = 128KB
  • read_map = 128KB


In the case where you are using read_lines() with a large file of filenames and are getting an error, the best workaround will be to split the large file by line count into multiple small files, scatter over the array of small files, and grab the filename by reading contents of each small file. This same concept can be applied to other read_X errors.

Here are two example WDLs for inspiration:

Option 1

workflow w {
  File fileOfFilenames # 1GB in size

  #Split large file into small individual files
  call splitFile { input: largeFile = fileOfFilenames }

 scatter (f in splitFile.tiny_files) {
    String fileName = read_string(f)   

  Array[String] filenames = fileName

task splitFile {
    File largeFile

    command {
        mkdir sandbox
        split -l 1 ${largeFile} sandbox/

    output {
        Array[File] tiny_files = glob("sandbox/*")
    runtime {
        docker: "ubuntu:latest"

Option 2

workflow use_file_of_filenames {
  File file_of_filenames
  call count_filenames_in_file { input: file_of_filenames = file_of_filenames }
  scatter (index in range(count_filenames_in_file.count)) {
    call operate_on_file { input: file_of_filenames = file_of_filenames, file_index = index }

task count_filenames_in_file {
  File file_of_filenames
  command {
    wc -l < ${file_of_filenames}
  output {
    Int count = read_int(stdout())

task operate_on_file {
  File file_of_filenames
  Int file_index
  command {
    # 1: Get the appropriate file name from the list
    # 2: Operate on that file as a URL

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