simple exec (no cgroups, docker or resource isolation)

[jippi]

hi,

a nice feature would be to have a very simple exec driver, that just runs a command

no fancy docker, cgroups or resource isolation - just running a command

would allow me to replace supervisord with nomad, and get a lot of the features I'm missing from supervisor backed right into nomad

[ghost]

There is one https://nomadproject.io/docs/drivers/exec.html

There are even Qemu and JVM drivers.

[jippi]

Every time I execute a job with exec my mount points gets messed up - some goes missing and it remounts the data dir as well -- currently it doesn't seem like the job is actually executed either, as nomad.out is nowhere to be found.

Example:

job "example" {
    # region = "global"
    datacenters = ["online"]
    type = "batch"
    priority = 50

    update {
        # Stagger updates every 10 seconds
        stagger = "10s"

        # Update a single task at a time
        max_parallel = 1
    }

    group "demo" {
        # Control the number of instances of this groups.
        # Defaults to 1
        # count = 1

        # Define a task to run
        task "date" {
            driver = "exec"

            config {
                command = "/bin/date > nomad.out"
            }

                        resources {
                                cpu = 500 # 500 Mhz
                        }
        }
    }
}

gives

==> Monitoring evaluation "c8587fb6-8043-d59c-db4e-32b9cce42997"
    Evaluation triggered by job "example"
    Allocation "b91276d6-cdd4-815b-48b6-d10d6377fe02" modified: node "ee0bd4c4-c1df-2ca1-c01d-7ac4c2138769", group "demo"
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "c8587fb6-8043-d59c-db4e-32b9cce42997" finished with status "complete"

and makes a new mount point on the box

/dev/disk/by-uuid/2778df7a-f8b9-4dc0-b2ba-71d76aea0261   12G  7.5G  3.2G  71% /opt/nomad/data/alloc/b91276d6-cdd4-815b-48b6-d10d6377fe02/date/alloc

and umounts devtmpfs and proc

before exec

-> df -h
Filesystem                                              Size  Used Avail Use% Mounted on
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   3.0G  216K  3.0G   1% /run
/dev/disk/by-uuid/2778df7a-f8b9-4dc0-b2ba-71d76aea0261   12G  7.4G  3.2G  70% /
tmpfs                                                   5.0M     0  5.0M   0% /run/lock
tmpfs                                                   6.1G     0  6.1G   0% /run/shm

after exec

-> df -h
df: `devtmpfs': No such file or directory
df: `proc': No such file or directory
Filesystem                                              Size  Used Avail Use% Mounted on
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   3.0G  220K  3.0G   1% /run
/dev/disk/by-uuid/2778df7a-f8b9-4dc0-b2ba-71d76aea0261   12G  7.5G  3.2G  71% /
tmpfs                                                   5.0M     0  5.0M   0% /run/lock
tmpfs                                                   6.1G     0  6.1G   0% /run/shm
/dev/disk/by-uuid/2778df7a-f8b9-4dc0-b2ba-71d76aea0261   12G  7.5G  3.2G  71% /opt/nomad/data/alloc/b91276d6-cdd4-815b-48b6-d10d6377fe02/date/alloc

[dadgar]

Hey,

Would you mind describing your environment? The mounts are a bit odd because they get cleaned up with the allocation is destroyed. This is hours after the job finishes which in a production environment gives you time to look at the logs or ship them. But when running locally it is undesirable. We will work on that.

BTW the stdout and stderr logs can be found in the tasks local directory. This can be found at /nomad_alloc_dir/alloc_id/task_name/local/task_name.stderr/stdout

[jippi]

Hi,

I'm running the 5 x nomad servers and 7 x nomad clients - with v0.1.0 - each on its own dedicated vm.

both the nomad servers and nomad clients are running inside a QEMU / KVM instance running Debian 7.8 with a custom 4.0.6 kernel

Is it possible to make a executor that won't touch anything, but simple exec a command without any server modifications ? :) I'm not looking for nomad for resource isolation, but simply a distributed executor in place of supervisord - which have plenty of pain points for us currently.

example fstab

UUID=2778df7a-f8b9-4dc0-b2ba-71d76aea0261 /                 ext4        rw,noatime,nodiratime,discard,nouser_xattr,barrier=0,data=ordered,errors=remount-ro     0       1
UUID=71570a26-77ff-4b86-a26d-9531dd0b4f35 none              swap        sw                                                      0       0
UUID=a779cc49-20be-4f23-bb5c-72d9f6713f54 /var/spool/postfix/   ext4            rw,noatime,nodiratime,discard,nouser_xattr,barrier=0,data=ordered,errors=remount-ro             0       0
tmpfs                                     /tmp                  tmpfs           rw,noatime,nodiratime,noatime,size=5g

[aldergren]

From my understanding of the code, the exec driver relies uses the executor to run your task within a per-task chroot. It will make some mounts available within this chroot but most won't be. Which mounts are accessible is currently not configurable. I have the same requirement as you and I'd be willing to attempt to write the code if there's consensus on a design that's likely to be accepted.

[wagnersza]

+1 simple exec (no cgroups, docker or resource isolation)

for instance, to run "puppet apply" command in the hosts.

[dadgar]

Just as an update, this is something we plan to support.

[dadgar]

We now have a raw_exec driver!

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