Added logic to read NetworkInfo from /state.json.

[ConnorDoyle]

Overview

Mesos 0.25.0 will include a new way for network isolation modules to communicate assigned IP addresses assigned to containers at executor launch time. Where previously Mesos-DNS picked up the values of some special labels appended to a task status, Mesos 0.25.0 introduces a new structure called NetworkInfo.

Change summary

This change preserves the previous behavior of reading special labels to ease transition to users who relied on that method of IP address discovery. However, the information in the new NetworkInfo structure should take precedence if present.

Additional references

• For general information on the NetworkInfo message and its intended use, see the public networking design document.
• For a different angle on how Framework developers will interact with new network isolation strategies in Mesos, see the public Framework writer’s guide to IP-per-container.
• For implementation details around NetworkInfo and its representation in the Mesos master state endpoint, see Review Request 38367: Added NetworkInfo message to ContainerInfo and TaskStatus by @karya0 .

[jdef]

may be interesting to filter on label here at some point in the future when there are multiple IPs

[ConnorDoyle]

I'm not even sure what Mesos-DNS should do when there are multiple addreses assigned. I think we'd need conventions for handling additional metadata to give us clues (e.g. labels on NetworkInfo, etc.)

[jdef]

Right, it's not clear to me either how mesos-dns should respond in
situations like that. It also just occurred to me that it might be nice to
include mention of this new behavior somewhere in the mesos-dns docs pages.

On Wed, Sep 16, 2015 at 7:15 PM, Connor Doyle [email protected]
wrote:

In records/state/state.go
#266 (comment):

@@ -103,7 +116,18 @@ func (t *Task) containerIP(src string) string {
continue
}

•   // find the latest docker-inspect label
  

•   // first try to extract the address from the NetworkInfo structure
  

•   if len(status.ContainerStatus.NetworkInfos) > 0 {
  

•       // TODO(CD): handle multiple NetworkInfo objects
  

•       // TODO(CD): only create A records if the address is IPv4
  

•       // TODO(CD): create AAAA records if the address is IPv6
  

•       latestContainerIP = status.ContainerStatus.NetworkInfos[0].IPAddress
  

I'm not even sure what Mesos-DNS should do when there are multiple
addreses assigned. I think we'd need conventions for handling additional
metadata to give us clues (e.g. labels on NetworkInfo, etc.)

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https://github.com/mesosphere/mesos-dns/pull/266/files#r39696900.

[jdef]

Great writeup! Thanks for all the context. Couple of minor comments but overall looking good. LGTM after comments addressed.

[ConnorDoyle]

Hey @tsenart, could you PTAL and merge if you don't find anything objectionable?

[tsenart]

How do we know if the IPAddress is v4 or v6? Are all clients supposed to try parsing one and then fallback?

[ConnorDoyle]

Yes, exactly. Using a string here was seen as a better alternative than trying to come up with a clever packed representation.

On Sep 17, 2015, at 01:39, Tomás Senart [email protected] wrote:

In records/state/state.go:

• Timestamp float64 json:"timestamp"
• State string json:"state"
• Labels []Label json:"labels,omitempty"
• ContainerStatus ContainerStatus json:"container_status,omitempty"
  +}

+// ContainerStatus holds container metadata as defined in the /state.json
+// Mesos HTTP endpoint.
+type ContainerStatus struct {

• NetworkInfos []NetworkInfo json:"network_infos,omitempty"
  +}

+// NetworkInfo holds a network address resolution as defined in the
+// /state.json Mesos HTTP endpoint.
+type NetworkInfo struct {

• IPAddress string json:"ip_address,omitempty"
  How do we know if the IPAddress is v4 or v6? Are all clients supposed to try parsing one and then fallback?

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[tsenart]

@ConnorDoyle: I'm briefly working on suggested change set that would set in place the constructs required to address your TODOs.

[tsenart]

PTAL: #267