[proxy] weavewait rewrites /etc/hosts so weave ip is returned first from 'hostname -i' #1079

paulbellamy · 2015-07-06T09:57:33Z

Partial fix for #68. Won't help with dynamic attach/detach or the weave script.

rade · 2015-07-06T11:21:42Z

I think this should close #68 and we should open a new issue (or issues) covering the remaining cases.

@bboreham would you mind reviewing this?

paulbellamy · 2015-07-06T12:35:23Z

I've tried this with Java's InetAddress.getLocalHost(), and it returns the weave address.

$ weave launch
$ docker $(weave proxy-config) run -ti --rm my-java-app
2c80b6ca84b7/10.128.0.2
$ docker run -ti --rm my-java-app
fc551c2b55a7/172.17.0.5

with code:

import java.net.InetAddress;

public class Main {
  public static void main(String[] args) {
    try {
      System.out.println(InetAddress.getLocalHost());
    } catch (java.net.UnknownHostException e) {
      System.out.println(e);
    }
  }
}

prog/weavewait/main.go

+	checkErr(err)
+	var oldHosts, newHosts bytes.Buffer
+	for _, addr := range addrs {
+		fmt.Fprint(&newHosts, strings.Split(addr.String(), "/")[0], "\t", hostname, "\n")


test/610_proxy_wait_for_weave_test.sh

@@ -19,4 +19,7 @@ COMMITTED_IMAGE=$(proxy docker_on $HOST1 commit c1)
 assert_raises "proxy docker_on $HOST1 run --name c2 $COMMITTED_IMAGE"
 assert "entrypoint c2" "$(entrypoint $COMMITTED_IMAGE)"

+# Check weave IP is first ip returned, so java (etc) prefer weave.
+assert "proxy docker_on $HOST1 run -e 'WEAVE_CIDR=10.2.1.1/24' $BASE_IMAGE hostname -i | cut -d' ' -f1" "10.2.1.1"


paulbellamy · 2015-07-06T15:12:44Z

As @bboreham points out above, afaict hostname -i makes no guarantees about order. Nor does Java.

If we want to add the ip hostname into /etc/hosts we could use docker's --add-hosts, but as hostname -I already returns the weave IP, I don't see the point of that.

rade · 2015-07-06T15:21:09Z

--add-host was considered in #68. It is of no use. The whole point of #68 is make hostname -i return the weave address. first.

We could remove the host entry for the docker ip.

paulbellamy · 2015-07-06T15:27:09Z

Yeah. removing the docker ip seems a bit naughty..

rade · 2015-07-06T15:32:12Z

Yeah. removing the docker ip seems a bit naughty.

Meh. The docker ip should still show up with hostname -I. Provided that both inbound and outbound docker links still work that is fine, I reckon. And we can add a flag for disabling that behaviour.

paulbellamy · 2015-07-06T15:56:41Z

Tried out links with the docker IP removed from /etc/hosts, and they still work fine. Not a big fan of adding yet another flag, but...

prog/weavewait/main.go

+		args         = os.Args[1:]
+		notInExec    = true
+		rewriteHosts = true
+	)

 	if args[0] == "-s" {


…rom 'hostname -i' Adds a --no-rewrite-hosts flag to the proxy, and be default, removes the docker IP from hosts. We only discard the docker host when it exists, so --net=none works.

prog/weavewait/main.go

+	writeHosts(hosts)
+}
+
+func parseHosts() map[string][]string {


tomwilkie · 2015-07-10T13:33:22Z

LGTM

prog/weavewait/main.go

+
+		fields := strings.Fields(line)
+		if len(fields) > 0 {
+			ips[fields[0]] = fields[1:]


LGTM. Closes #68, with remainder to #1122

paulbellamy assigned rade Jul 6, 2015

rade assigned bboreham and unassigned rade Jul 6, 2015

bboreham reviewed Jul 6, 2015
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prog/weavewait/main.go

checkErr(err)

var oldHosts, newHosts bytes.Buffer

for _, addr := range addrs {

fmt.Fprint(&newHosts, strings.Split(addr.String(), "/")[0], "\t", hostname, "\n")

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paulbellamy force-pushed the 68-rewrite-etc-hosts branch from 93e934a to 8652ba2 Compare July 6, 2015 13:40

bboreham reviewed Jul 6, 2015
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bboreham assigned paulbellamy and unassigned bboreham Jul 6, 2015

paulbellamy force-pushed the 68-rewrite-etc-hosts branch from 8652ba2 to 0e74e46 Compare July 6, 2015 15:14

paulbellamy force-pushed the 68-rewrite-etc-hosts branch from eb8ed82 to ea52cfd Compare July 7, 2015 10:41

paulbellamy assigned rade and unassigned paulbellamy Jul 7, 2015

rade removed their assignment Jul 7, 2015

paulbellamy force-pushed the 68-rewrite-etc-hosts branch from ea52cfd to 386e358 Compare July 7, 2015 14:50

tomwilkie reviewed Jul 9, 2015
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prog/weavewait/main.go

args = os.Args[1:]

notInExec = true

rewriteHosts = true

)

if args[0] == "-s" {

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paulbellamy force-pushed the 68-rewrite-etc-hosts branch 2 times, most recently from ce441c9 to e445837 Compare July 10, 2015 12:57

[proxy] weavewait rewrites /etc/hosts so weave ip is returned first f…

e445837

…rom 'hostname -i' Adds a --no-rewrite-hosts flag to the proxy, and be default, removes the docker IP from hosts. We only discard the docker host when it exists, so --net=none works.

tomwilkie reviewed Jul 10, 2015
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prog/weavewait/main.go

writeHosts(hosts)

}

func parseHosts() map[string][]string {

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rade assigned bboreham Jul 10, 2015

bboreham reviewed Jul 10, 2015
View reviewed changes

prog/weavewait/main.go

fields := strings.Fields(line)

if len(fields) > 0 {

ips[fields[0]] = fields[1:]

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bboreham assigned paulbellamy and unassigned bboreham Jul 10, 2015

Review feedback

fa67770

paulbellamy assigned bboreham and unassigned paulbellamy Jul 10, 2015

bboreham mentioned this pull request Jul 13, 2015

Make weave IP preferred in /etc/hosts lookup, for 'attach'-ed addresses #1122

Open

bboreham added a commit that referenced this pull request Jul 13, 2015

Merge pull request #1079 from weaveworks/68-rewrite-etc-hosts

5e43f0f

LGTM. Closes #68, with remainder to #1122

bboreham merged commit 5e43f0f into master Jul 13, 2015

paulbellamy deleted the 68-rewrite-etc-hosts branch July 13, 2015 10:19

rade modified the milestones: current, 1.1.0 Jul 13, 2015

rade mentioned this pull request Aug 4, 2015

weave does not set ip address in docker container in docker 1.7.0 #1233

Closed

rade mentioned this pull request Aug 31, 2015

document --no-rewrite-hosts #1373

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[proxy] weavewait rewrites /etc/hosts so weave ip is returned first from 'hostname -i' #1079

[proxy] weavewait rewrites /etc/hosts so weave ip is returned first from 'hostname -i' #1079

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tomwilkie commented Jul 10, 2015

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[proxy] weavewait rewrites /etc/hosts so weave ip is returned first from 'hostname -i' #1079

[proxy] weavewait rewrites /etc/hosts so weave ip is returned first from 'hostname -i' #1079

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