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From Gastón Kleiman (JIRA) <j...@apache.org>
Subject [jira] [Commented] (MESOS-5961) HTTP and TCP health checks should support docker executor and bridged mode.
Date Thu, 04 Aug 2016 13:55:20 GMT

    [ https://issues.apache.org/jira/browse/MESOS-5961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15407800#comment-15407800
] 

Gastón Kleiman commented on MESOS-5961:
---------------------------------------

h1. Summary / Suggested Solution
To keep the implementation simple and consistent, I propose that the Docker executor's health
check thread should always enter the task's net namespace and connect to {{localhost}} on
the port specified in the health check proto.

The framework would then be responsible for deciding if the health checker should connect
to the {{containerPort} or the {{hostPort}}.

h1. Testing results
h2. HOST networking
# Connect to {{localhost:<hostPort>}}.
# Enter the container's net ns and connect to {{localhost:<hostPort>}}.

h2. BRIDGED networking
# Connect to {{localhost:<hostPort>}}.
# Enter the container's net ns and connect to {{localhost:<containerPort>}}.

h2. USER networking (DC/OS Overlay network)
# If the task specifies a {{hostPort}}, connect to {{localhost:<hostPort>}}.
# If the task doesn't use a host port, enter the container's net ns and connect to {{localhost:<containerPort>}}.
I expect this to be the most common case.

h1. Testing notes
h2. Getting the networking namespace
{code}
NETNS="/proc/`docker inspect -f '{{.State.Pid}}' <container id>`/ns/net"
{code}

h2. Test Utility
The following utility enters a network namespace and does an HTTP request.

{code}
package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"syscall"

	"github.com/opencontainers/runc/libcontainer/system"
)

func doNetns(nsPath string) error {
	ns, err := os.Open(nsPath)
	if err != nil {
		return err
	}
	return system.Setns(ns.Fd(), syscall.CLONE_NEWNET)
}

func doGet(port string) {
	response, err := http.Get("http://localhost:" + port)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%s\n", err)
	} else {
		defer response.Body.Close()
		_, err := io.Copy(os.Stderr, response.Body)
		if err != nil {
			fmt.Fprintf(os.Stderr, "%s\n", err)
		}
	}
}

func main() {
	doNetns(os.Args[1])
	doGet(os.Args[2])
}
{code}

h2. Marathon App Definitions
h3. HOST networking
{code}
{
  "id": "/host",
  "cmd": "python -m SimpleHTTPServer $PORT0",
  "cpus": 0.1,
  "mem": 32,
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "python:2",
      "network": "HOST"
    }
  },
  "portDefinitions": [
    {
      "name": "http",
      "protocol": "tcp"
     }
  ]
}
{code}

h3. BRIDGE networking
{code}
{
  "id": "/bridged",
  "cmd": "python -m SimpleHTTPServer 31337",
  "cpus": 0.1,
  "mem": 32,
  "container": {
    "type": "DOCKER",
    "docker": {
      "image": "python:2",
      "network": "BRIDGE",
      "portMappings": [
        {
          "containerPort": 31337,
          "hostPort": 0,
          "name": "http"
        }
      ]
    }
  }
}
{code}

h3. USER networking (DC/OS Overlay network)
{code}
{
  "id": "/overlay",
  "cpus": 0.1,
  "mem": 32,
  "cmd": "python -m SimpleHTTPServer 31337",
  "container": {
   "type": "DOCKER",
    "docker": {
      "network": "USER",
      "image": "python:2",
      "portMappings": [
        {
          "containerPort": 31337,
          "protocol": "tcp",
          "name": "http"
        }
      ]
    }
  },
  "ipAddress": {
    "networkName": "dcos"
  }
}
{code}



> HTTP and TCP health checks should support docker executor and bridged mode.
> ---------------------------------------------------------------------------
>
>                 Key: MESOS-5961
>                 URL: https://issues.apache.org/jira/browse/MESOS-5961
>             Project: Mesos
>          Issue Type: Improvement
>            Reporter: Alexander Rukletsov
>            Assignee: haosdent
>              Labels: health-check, mesosphere
>
> If an executor and a task, e.g. the docker executor and docker container in bridged mode,
exist is different network namespaces, HTTP and TCP health checks using {{localhost}} may
not work properly. One solution would be to enter the container's network in the health check
binary.



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