Pipes/redirection and stdout/stdin

[Cristina Luis]

Hi, 

I'm trying to run a couple of chained tasks in a Docker container as a Nomad task and have run into some difficulties.

A command that works outside of Nomad:

 docker run --rm -it ourtask/image:latest sh -c "task arg1 --arg2 val2 | task arga argb"

The only success I've had is by just running the first task as a command. Relevant portion of job spec:

task "loader" {

driver = "docker"

config {

image = "ourtask/image:latest"

command = "task" 

args = [

"arg1",

"--arg2", "val2"

]

}

If I use "sh" as the command with ["task", "arg1", "--arg2", "val2"] as the list of arguments then 'task' gets run but doesn't seem to be receiving the arguments. 

The success example does appear to run properly, based on the log output at alloc/log/loader.stderr.0 but the output of the task, which is emitted to stdout, is nowhere to be found.

So there are two main problems:

1. Passing in a command and args so that the entire line is executed. I realize there are other possibilities, e.g. using artifacts to define more complex config options, but we'll be generating a lot of different jobs using the same tasks and it would be most clear if everything were defined in the job specs. 

2. Where is the output? It won't matter if I can run the whole line if there's no stdout to redirect to the next one.

Thanks,

Cristina 

(Nomad & Docker newbie)

[Alex Dadgar]

Hey Cristina,

You can get the arguments to be passed by running:

config {

image = "ourtask/image:latest"

command = "sh" 

args = [

"-c",

"arg1 --arg2 val2"

]

}

As for the logs you can access them via: `nomad fs <alloc-id> alloc/logs/`. That will list the log files and then if you add the file name it will cat them. This workflow will be made easier soon!

Thanks,

Alex

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[Cristina Luis]

Hi Alex,

Aha, that does work for the whole command with the pipe, thanks! 

There still seems to be a problem with the stdout output when I run just the first task script -- there's nothing in the stdout log (from nomad fs <alloc-id> alloc/logs/). When I add the pipe and the second task script I do get output (from the second task script) in stdout, so the information exists and is getting redirected, but there's no sign of it if I just run the one by itself. Is there some other place it could end up, or something that could cause it not to be saved in the logs? 

Thanks,

Cristina

[Alex Dadgar]

Hey Cristina,

If you can run the task locally and it prints to stdout then it should work on Nomad as well. Be aware on your terminal you are seeing both stdout and stderr together. So it may be in the stderr file!

Thanks,

Alex

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