embed: warns about empty hosts in advertise urls

[gyuho]

Address #8379.

./bin/etcd --listen-client-urls=http://127.0.0.1:2379 --advertise-client-urls=http://$SPELEDOK:2379

2017-08-09 13:34:52.220844 E | etcdmain: error verifying flags, unexpected empty host (http://:2379). See 'etcd --help'.

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Codecov Report

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The diff coverage is 33.33%.

@@            Coverage Diff            @@
##             master    #8384   +/-   ##
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  Coverage          ?   76.97%           
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  Hits              ?    21652           
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Impacted Files	Coverage Δ
embed/config.go	66.19% <33.33%> (ø)

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[heyitsanthony]

I tried some empty host url abuse.

./etcd defaults:

$ ETCDCTL_API=3 ./bin/etcdctl --endpoints=http://:2379 endpoint status
http://:2379, 8e9e05c52164694d, 3.2.0+git, 16 kB, true, 10, 20

fails because of IP check:

$ ./bin/etcd --listen-client-urls=http://:2379 --advertise-client-urls=http://:2379
etcdmain: error verifying flags, expected IP in URL for binding (http://:2379). 

(fixed by this patch):

$ ./bin/etcd --listen-client-urls=http://0.0.0.0:2379 --advertise-client-urls=http://:2379

Does anyone use the empty host => any address behavior? A workaround like this seems tempting:

$ ETCDCTL_API=3 ./bin/etcdctl --endpoints=http://0.0.0.0:2379 endpoint status
http://0.0.0.0:2379, 8e9e05c52164694d, 3.2.0+git, 16 kB, true, 12, 24

but that only binds to any ipv4 address instead of any address.

On the other hand, empty hosts fail the curl sanity test:

$ curl http://:2379/
curl: (6) Could not resolve host: 
$ curl http://localhost:2379/health
{"health":true}
$ wget http://:2379/health
http://:2379/health: Invalid host name.

If etcd is advertising a client address curl can't parse, that must be broken. Maybe someone somewhere somehow relies on this though. Can this be a warning in 3.3 then a full error/exit in 3.4?

[gyuho]

@heyitsanthony PTAL. Now just logs warnings.

Thanks.

[heyitsanthony]

should these say something like "advertise-peer-urls %q is deprecated (%v)" if the intent is to eventually exit out? warning with only the error doesn't seem clear enough

[gyuho]

@heyitsanthony PTAL. Now

./bin/etcd --listen-client-urls=http://127.0.0.1:2379 --advertise-client-urls=http://$SPELEDOK:2379
2017-08-10 12:33:58.211006 W | embed: advertise-client-urls "http://:2379" is deprecated (unexpected empty host (http://:2379))

Thanks.

[heyitsanthony]

lgtm thanks