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From "Qian Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (MESOS-7709) Add --dns flag to the agent.
Date Tue, 27 Jun 2017 06:53:00 GMT

    [ https://issues.apache.org/jira/browse/MESOS-7709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16061870#comment-16061870
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Qian Zhang edited comment on MESOS-7709 at 6/27/17 6:52 AM:
------------------------------------------------------------

{quote}
The problem becomes even more acerbated when you have a mix of v4 and v6 containers, since
if now you rely only on `/etc/resolv.conf` to provide the default you will have pick some
of the 3 possible nameservers to v4 and some to v6 again making it inflexible.
{quote}
Do you mean the case that there are some v4 containers and some v6 containers in the same
agent host? And if we introduce a {{--dns}} agent flag, how will the issue you mentioned be
resolved? Thanks.

Update:
Had a sync up with Avinash in Slack, the idea is, in a Mesos cluster which has both IPv4 containers
and IPv6 containers, without the {{\--dns}} agent flag either the frameworks will have to
explicitly set a IPv6 DNS entry for v6 containers using the {{\--dns}} parameter to {{docker
run}}, or we will need to have IPv6 entry for {{nameservers}} in our {{/etc/resolv.conf}}.
With the introduction of the {{\--dns}} flag this problem goes away since for IPv6 networks
the operator can just set a nameserver (multiple of them if necessary) for a given network
and we can pass these values to the docker daemon when launching the docker container on that
IPv6 network.


was (Author: qianzhang):
{quote}
The problem becomes even more acerbated when you have a mix of v4 and v6 containers, since
if now you rely only on `/etc/resolv.conf` to provide the default you will have pick some
of the 3 possible nameservers to v4 and some to v6 again making it inflexible.
{quote}
Do you mean the case that there are some v4 containers and some v6 containers in the same
agent host? And if we introduce a {{--dns}} agent flag, how will the issue you mentioned be
resolved? Thanks.

> Add --dns flag to the agent.
> ----------------------------
>
>                 Key: MESOS-7709
>                 URL: https://issues.apache.org/jira/browse/MESOS-7709
>             Project: Mesos
>          Issue Type: Task
>          Components: containerization
>            Reporter: Avinash Sridharan
>            Assignee: Avinash Sridharan
>
> Mesos support both CNI (through `network/cni` isolator) and CNM (through docker) specification.
Both these specifications allow for DNS entries for containers to be set on a per-container,
and per-network basis. 
> Currently, the behavior of the agent is to use the DNS nameservers set in /etc/resolv.conf
when the CNI or CNM plugin that is used to attached the container to the CNI/CNM network doesnt'
explicitly set the DNS for the container. This is a bit inflexible especially when we have
a mix of v4 and v6 networks. 
> The operator should be able to specify DNS nameservers for the networks he installs either
the override the ones provided by the plugin or as defaults when the plugins are not going
to specify DNS name servers.
> In order to achieve the above goal we need to introduce a `\--dns` flag to the agent.
The `\--dns` flag should support a JSON (or a JSON file) with the following schema:
> {code}
> {
>   "mesos": {
>     [ 
>       {
>         "network" : <name of the network>,
>         "nameservers": [<list of name servers (upto 3)>]
>       }
>     ]
>   },
>   "docker": {
>     [ 
>       {
>         "network" : <name of the network>,
>         "nameservers": [<list of name servers (upto 3)>]
>       }
>     ]
>   }
> }
> {code}



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