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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:
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{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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