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DNS query failed in k8s by service name #1694

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dawnbreaks opened this issue Apr 4, 2019 · 9 comments · Fixed by #1697
Closed

DNS query failed in k8s by service name #1694

dawnbreaks opened this issue Apr 4, 2019 · 9 comments · Fixed by #1697
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defect
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0.84.0

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@dawnbreaks
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Hi, the DnsAddressEndpointGroup can not resolve successfully by the k8s service name, and must use a fully qualified domain name.
e.g.

//query failed
new DnsAddressEndpointGroupBuilder("service-a").port(8080).build()
//only a fully qualified domain name work
new DnsAddressEndpointGroupBuilder("service-a.infra.svc.cluster.local").port(8080).build()
@dawnbreaks dawnbreaks changed the title DNS query failed in kubernetes by service name DNS query failed in k8s by service name Apr 4, 2019
@trustin
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trustin commented Apr 4, 2019

Hi! Could you paste your /etc/hosts and /etc/resolv.conf? IIUC, /etc/resolv.conf must contain the following lines:

search infra.svc.cluster.local svc.cluster.local cluster.local 
options ndots:5

@dawnbreaks
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Yes, the /etc/resolv.conf do contains the search options. It seem that armeria always transform a relative dns name to absulute one by adding a trailing dot at the end of the host name.

nameserver 192.168.80.10
search infra.svc.cluster.local svc.cluster.local cluster.local localdomain
options ndots:5

@dawnbreaks
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Hi, the DefaultDnsQuestion in netty will transform a relative dns name to an absolute one. So the search options will never work.

@trustin
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trustin commented Apr 4, 2019

Let us investigate this further. Thanks for reporting. 👍

@trustin trustin added the defect label Apr 4, 2019
@trustin trustin added this to the 0.84.0 milestone Apr 4, 2019
@trustin
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trustin commented Apr 4, 2019

One more question: Could you set the log level of io.netty.resolver.dns.TraceDnsQueryLifeCycleObserverFactory logger to DEBUG to see what DNS queries Netty sends?

@trustin
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trustin commented Apr 4, 2019

.. and could you also let us know the version of Armeria and Netty in your class path?

@dawnbreaks
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armeria version: 0.82.0
netty version: 4.1.33.final

the parent class of DefaultDnsQuestion append the trailing dot to the host name, Please refer to this file AbstractDnsRecord

trustin added a commit to trustin/armeria that referenced this issue Apr 4, 2019
@trustin
Fix a bug where DnsEndpointGroup does not respect search domains in…
ff877ce 
… `/etc/resolv.conf`

Motivation:

When using `Dns*EndpointGroup` with search domains in
`/etc/resolv.conf`, the resolver should try all search domains until the
host name is resolved.

However, it treats the specified host name as a full domain name by
appending a dot (.) to the specified host name.

Modifications:

- Introduce a new `DnsQuestion` implementation called
  `DnsQuestionWithoutTrailingDot` which does not append a dot at the end
  of the host name.

Result:

- `Dns*EndpointGroup` respects the search domains in `/etc/resolv.conf`.
- Fixes line#1694
@trustin trustin mentioned this issue Apr 4, 2019
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@trustin
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trustin commented Apr 4, 2019

Should be fixed with #1697. Please give it a try if you don't mind building Armeria by yourself.

@dawnbreaks
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Great. I'm on vacation, and will have a try next week. It 'would be appreciated that An new release that fixed this issue will be made soon.

trustin added a commit that referenced this issue Apr 5, 2019
@trustin
Fix a bug where DnsEndpointGroup does not respect search domains in…
826f520 
… `/etc/resolv.conf` (#1697)

Motivation:

When using `Dns*EndpointGroup` with search domains in
`/etc/resolv.conf`, the resolver should try all search domains until the
host name is resolved.

However, it treats the specified host name as a full domain name by
appending a dot (.) to the specified host name.

Modifications:

- Introduce a new `DnsQuestion` implementation called
  `DnsQuestionWithoutTrailingDot` which does not append a dot at the end
  of the host name.

Result:

- `Dns*EndpointGroup` respects the search domains in `/etc/resolv.conf`.
- Fixes #1694
fmguerreiro pushed a commit to fmguerreiro/armeria that referenced this issue Sep 19, 2020
@trustin
Fix a bug where DnsEndpointGroup does not respect search domains in…
aba5ee9 
… `/etc/resolv.conf` (line#1697)

Motivation:

When using `Dns*EndpointGroup` with search domains in
`/etc/resolv.conf`, the resolver should try all search domains until the
host name is resolved.

However, it treats the specified host name as a full domain name by
appending a dot (.) to the specified host name.

Modifications:

- Introduce a new `DnsQuestion` implementation called
  `DnsQuestionWithoutTrailingDot` which does not append a dot at the end
  of the host name.

Result:

- `Dns*EndpointGroup` respects the search domains in `/etc/resolv.conf`.
- Fixes line#1694
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Fix a bug where DnsEndpointGroup does not respect search domains trustin/armeria
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