> On Jul 19, 2017, at 10:05 AM, Thomas HUMMEL wrote:
>
> Hello,
>
> I've read some books about Mesos, installed one multi-master cluster (for POC
> purposes) with some frameworks (Marathon, Spark for instance) and watch some
> talks.
>
> Everything works and my understanding of Mesos is becoming clearer.
> However, I'm having a hard time fully understanding this section of the
> documentation :
>
> http://mesos.apache.org/documentation/latest/containerizer-internals/
>
> Note :
>
> - my understanding is that Mesos is now heading towards a universal
> containerizer, which is able to understand docker (among others) images thus
> beeing able to "do some docker" without a docker daemon.
>
> - Also, I don't think Mesos supports nester containers yet either.
http://mesos.apache.org/documentation/latest/nested-container-and-task-group/
>
> But I'm not really sure about what is the mesos-docker-executor, as opposed
> to mesos-executor.
>
> - For instance, in the "A)" case of the slave running in a container, the doc
> states :
>
> "if the task does not include an executor i.e. it defines a command, the
> default executor mesos-docker-executor is launched in a docker container to
> execute the command via Docker CLI."
>
> Why Docker CLI ? We are not in a shell context, are we ?
> Also, will the command be launched in another docker container, different
> from the one running mesos-docker-executor ?
>
> - In the B) case where the slave is not running in a container, the doc
> states :
>
> "If task does not include an executor i.e. it defines a command, a subprocess
> is forked to execute the default executor mesos-docker-executor.
> mesos-docker-executor then spawns a shell to execute the command via Docker
> CLI."
>
> Why is the mesos-docker-executor not run in a container ? Also, why does it
> not use docker API directly ?
>
> Can you help me figuring out how exactly mesos-docker-executor works and what
> its specificality relative to the mesos-executor ?
From the scheduler's POV, I'd say you don't really need to know the difference.
In the API you need to specify the container type to switch between using the
Docker containerized and the Mesos containerizer. For example, you can
experiment by passing JSON to the --task option of mesos-execute:
{
"name": "sleep",
"agent_id": { "value": "any" },
"task_id": {
"value": "some-unique-uuid"
},
"resources": [
{
"name": "cpus",
"type": "SCALAR",
"scalar": {
"value": 0.4
},
"role": "*"
},
{
"name": "mem",
"type": "SCALAR",
"scalar": {
"value": 32
},
"role": "*"
}
],
"command": {
"value": "command-line that you want to run",
"environment": {
" variables": [
{ "name": "GLOG_v", "value": "2" }
]
}
},
"container": {
"type": "MESOS",
"mesos": {
"image": {
"type": "DOCKER",
"docker": {
"name": "image/name"
}
}
}
}
}
