Suspected memory leak in database backup script - memory-leaks

Question

I have the following database backup script which runs once every hour.
I recently began seeing my docked-deployed Elixir application crash with the following error message:
Crash dump is being written to: erl_crash.dump...done
2016-07-27T11:05:39.754630931Z app[web.1]: binary_alloc: Cannot allocate 124512968 bytes of memory (of type "binary").
My database has been increasing steadily and it is around 130mb now.
I use the script below to do the backup and upload to So. Are there any obvious faults here which may lead to such a memory crash?
defmodule MyApp.Backup do
require Logger
alias MyApp.{ Repo, BackupUploader, S3 }
#database System.get_env("DATABASE_URL")
#bucket Application.get_env(:arc, :bucket)
#folder "backups"
def start do
Logger.info "*** Initiating database backup ***"
backup = %BackupRequest{}
backup
|> dump_database
|> upload_to_s3
end
defp dump_database(%BackupRequest{} = backup) do
Logger.info "*** Dumping database ***"
command = "pg_dump"
args = [#database]
{data, 0} = System.cmd command, args
%{backup | data: data, status: "dumped"}
end
defp upload_to_s3(%BackupRequest{data: data} = backup) do
Logger.info "*** Uploading to S3 bucket ***"
key = get_s3_key
ExAws.S3.put_object!(#bucket, key, data)
Logger.info "*** Backup complete ***"
end
# Helpers
#
#
defp get_s3_key do
{{year, month, day}, {hour, minute, _seconds}} = :os.timestamp |> :calendar.now_to_datetime
hash = SecureRandom.urlsafe_base64(32)
date = "#{day}-#{month}-#{year}-#{hour}:#{minute}"
key = #folder <> "/#{date}_#{hash}_#{Mix.env}"
key
end
end