Run Mix task in crontab

saggit

Hi, everybody
I was try to use crontab to schedule my simple mix task that send emails, the task works perfect by run
mix hello.greeting but does not work (scheduled, but no email sent ) if i put something like this in crontab */5 * * * * cd path/to/myapp; /usr/local/bin/mix hello.greeting

my simple task code

defmodule Mix.Tasks.Hello.Greeting do
  use Mix.Task

  alias Hwapp.Email
  alias Hwapp.Mailer

  @shortdoc "Sends a greeting to us from Hello Phoenix"

  @moduledoc """
    This is where we would put any long form documentation or doctests.
  """

  def run(_args) do
    Mix.shell.info("Greetings from the Hello Phoenix Application!")
    Mix.Task.run "app.start"
    # get all users
    "hello@localhost"
    		Email.welcome_html_email()
    		|> Mailer.deliver_now
    	end)
   end

end

Thanks for your time.

8 comments

#mix #crontab

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2019-04-25 02:03:28 UTC

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speeddragon

You can put that code cd path/to/myapp; /usr/local/bin/mix hello.greeting inside a shell script (something.sh) give +x permission (chmod +x something.sh) and then call it on the crontab. Don’t forget to use full path instead of relative paths.

Post #1

saggit

Thanks for your reply, I tried and got the same result, Just wonder if I got something wrong.

Post #2

NobbZ

Does cron send you any logs? If not please activate the feature to send you the logs of each run to your local address for the debugging period at least(*).

Also, how are you editing your crontab? If you do not use crontab -e(*) Cron won’t know about the changes and nothing will be run of course.

Have you made sure that the project folder and all folders above and below and the files are actually readable/accessible by the user that owns the crontab in question?

(*): Can’t look up details or exact command as I’m on mobile right now.

Post #3

saggit

Hi Nobbz, Thanks for your reply, tail -f /var/log/cron.log give me correct execute log say every 5 minutes without error message so that mean the path are correct and command run without error. I have to do more check. But thanks.

Post #4

NobbZ

As far as I remember Cron log will only contain that a job has started, it will not contain it’s results. Please try writing into a file, use the wrapper script from before and change it to be like this:

cd /path/to/project
mix hello.greeting >> /tmp/greeting.log

Post #5

speeddragon

Finally got it working. Here is the steps done in my computer (running OSX), it might change a little bit if you use Linux.

I’ve created a script with the following code:

#!/bin/bash
cd /path/project
mix phx.server&

And run with the following line on crontab:

*/1 * * * * /tmp/test.sh >> /var/log/crontab.log 2>&1

The output of crontab.log was showing this:

/tmp/test.sh: line 2: mix: command not found

Using the full path of mix didn’t solve it. (/usr/local/bin/mix phx.server)

env: elixir: No such file or directory

Searching that on google, I found an comment from José Valim, Ability to use elixir commands that shipped as an application dependency · Issue #789 · elixir-lang/elixir · GitHub

But even using /usr/local/bin/elixir /usr/local/bin/mix phx.server & didn’t solve it, because it gave the following error:

/usr/local/bin/elixir: line 123: exec: erl: not found

So, if you output the $PATH, you will see that only have 2 directories (or less than you expected): /usr/bin:/bin

You can check where is your binaries, with the command which, like which elixir. You will need in your path at least for mix, elixir and erl.

In the final script, you should export PATH concatenating the missing path, in my case was /usr/local/bin/.