As said, I only use persistent volumes with my only scheduler straight
on Mesos so do not exactly know how this works in Marathon...
The persistent volume is created on a Mesos agent and basically ends up
being a folder on that hosts disk. So yes, you can not use the volume on
a different agent/slave. For marathon you would need to set a hostname
constraint that makes sure the same host is used when restarting the
task. You won't be able to use fail over to different agents just have
Marathon restart your task once it fails. Also only one task at a time
can have the volume bound.
Yes, you can achieve persistence in pretty much the same way by using a
hostpath but then you are using implicit knowledge about your
environment, which is not very clean in my opinion, and thus have a
tighter coupling. The nice thing about persistent volumes is that they
are managed by Mesos. I do not need to tell the Mesos admin that I need
space at some location. I do not need to do something special if I have
multiple instances running as they get all their own directory. And I
can programatically destroy the volume and then the directory on the
host gets deleted again (at least since Mesos 1.0). So in my opinion the
usage of persistent volumes is much cleaner. But there are certainly use
cases that do not really work with them, like being able to fail over to
different host. For that you would wither need a shared network mount or
storage like HDFS. Btw, the Mesos containerizer should also enforce disk
quotas so your task would not be able to fill the filesystem.
On 27.11.2017 16:11, Dino Lokmic wrote:
yes I did. So I don't have to prepare it before task? I can't use
volume created on slave A, from slave B
Once task fails where will it be restarted? Do I have to specify host?
If I do, it means I can achieve "persistence" same way I deploy now,
by specifying hostpath for volume and hostname
....
"constraints": [
[
"hostname",
"CLUSTER",
"MYHOSTNAME"
]
],
"container": {
"type": "DOCKER",
"volumes": [
{
"containerPath": "/opt/storm/storm-local",
"hostPath": "/opt/docker_data/storm/storm-local",
"mode": "RW"
},
{
"containerPath": "/opt/storm/logs",
"hostPath": "/opt/docker_logs/storm/logs",
"mode": "RW"
},
{
"containerPath": "/home/xx/runtime/storm",
"hostPath": "/home/xx/runtime/storm",
"mode": "RO"
}
],
"docker": {
"image": "xxx/storm-1.1.0",
"network": "HOST",
"portMappings": [],
"privileged": false,
"parameters": [],
"forcePullImage": true
}
},
....
On Mon, Nov 27, 2017 at 3:05 PM, Hendrik Haddorp
<[email protected] <mailto:[email protected]>> wrote:
I have my own scheduler that is performing a create operation. As
you are using Marathon this call would have to be done by Marathon.
Did you read
https://mesosphere.github.io/marathon/docs/persistent-volumes.html
<https://mesosphere.github.io/marathon/docs/persistent-volumes.html> ?
On 27.11.2017 14:59, Dino Lokmic wrote:
@hendrik
How did you create this
"my-volume-227927c2-3266-412b-8572-92c5c93c051a" volume?
On Mon, Nov 27, 2017 at 7:59 AM, Hendrik Haddorp
<[email protected] <mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>> wrote:
Hi,
I'm using persistent volumes directly on Mesos, without
Marathon.
For that the scheduler (like Marathon) has to first
reserve disk
space and then create a persistent volume with that. The next
resource offer message then contain the volume in "disk"
resource
part of the offer. Now you can start your task. In the
request you
would need to include the resources and for the
"container" part
of the request you would have:
volumes {
container_path: "/mount/point/in/container"
host_path:
"my-volume-227927c2-3266-412b-8572-92c5c93c051a"
mode: RW
}
The container path is the mount point in your container
and the
host path is the id of your persistent volume.
In case you use marathon the documentation should be this:
https://mesosphere.github.io/marathon/docs/persistent-volumes.html
<https://mesosphere.github.io/marathon/docs/persistent-volumes.html>
<https://mesosphere.github.io/marathon/docs/persistent-volumes.html
<https://mesosphere.github.io/marathon/docs/persistent-volumes.html>>
regards,
Hendrik
On 23.11.2017 10:00, Dino Lokmic wrote:
I have few machines on Linode and I run Mesos there. Can
someone explain to me, how to set volumes right.
Now I run taks via marathon like this
...
"constraints": [
[
"hostname",
"CLUSTER",
"HOSTNAME"
]
],
"container": {
"type": "DOCKER",
"volumes": [
{
"containerPath": "/opt/storm/storm-local",
"hostPath": "/opt/docker_data/storm/storm-local",
"mode": "RW"
}
],
"docker": {
"image": "xxxx",
"network": "HOST",
"portMappings": [],
"privileged": false,
"parameters": [],
"forcePullImage": true
}
},
...
So if task is restarted I can be sure it has access to
previously used data.
You can see I have scaling problem and my task is
depending on
this node.
I would like for my apps to be node independent and
also that
they have redundant data.
What is best practice for this?
I want to scale aplication to 2 instances, I1 and I2
Instance I1 runs on agent A1 and uses volume V1
Instance I2 runs on agent A2 and uses volume V2
If agent A1 stops, I1 is restared to A3 and uses V1
If V1 failes I1 uses copy of data from V3...
Can someone point to article describing this, or at
least give
me few "keywords"
Thanks
