> On Sept. 18, 2015, 10:57 p.m., Cong Wang wrote:
> > Why not just set --host_name=$LIBPROCESS_IP for your case since you anyway 
> > need to provide a flag?
> 
> Guangya Liu wrote:
>     I also have the same question with Cong, @Marco, can you please show more 
> detail for why not using the solution as above? What is the benefit of this 
> compared to using --host_name=$LIBPROCESS_IP? Thanks.
> 
> Marco Massenzio wrote:
>     `$LIBPROCESS_IP` may not be set by the time we run the binary - it is 
> actually set in the `main()` method (of both Master/Agent) after parsing the 
> `--ip` (and `--ip_discovery_command`) flags.
>     
>     The reason I use `LIBPROCESS_IP` here is to ensure that the IP used by 
> `libprocess` (which is initialized before creating the `Master` or `Slave` 
> object) is consistent with what the `Master/Agent` will be configured with.
>     
>     Please also refer to the conversation about the introduction of 
> `--ip_discovery_command` as to why we need a "dynamic" way of configuring 
> hostname/IP - it all boils down to make Mesos play nice in various Cloud (and 
> Enterprise data centers) where the DNS resolution (and hostname configuration 
> of VMs) is vastly different and may not necessarily conform to the generally 
> assumed scenario, where IP/hostname are kept in sync / resolved by the OS 
> and/or external services (DHCP/DNS).
> 
> Qian Zhang wrote:
>     If you want to set hostname to the chosen IP, then I think you can just 
> use the existing flag "--hostname" (set it to the chosen IP manually). And if 
> "--hostname" is set, then I think the hostname lookup will be bypassed. So 
> why do we need to introduce a new flag "--no_hostname_lookup"?
> 
> Marco Massenzio wrote:
>     Please refer to the conversation on 
> https://issues.apache.org/jira/browse/MESOS-3154 for why this may not be 
> possible in the above-mentioned environments.
>     (and, yes, we do know about the `--hostname` flag - unfortunately, under 
> certain scenarios, it's not possible to set it to a "static" value)

Makes sense for me, can you document it in configuration.md too? Thanks.


- Cong


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On Sept. 19, 2015, 1:25 a.m., Marco Massenzio wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/38473/
> -----------------------------------------------------------
> 
> (Updated Sept. 19, 2015, 1:25 a.m.)
> 
> 
> Review request for mesos, Benjamin Hindman, Cody Maloney, and Neil Conway.
> 
> 
> Bugs: MESOS-3457
>     https://issues.apache.org/jira/browse/MESOS-3457
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Under certain circumstances, dynamic lookup of hostname, while
> successful, provides undesirable results; we would also like, in
> those circumstances, be able to just set the hostname to the chosen
> IP address (possibly set via the --ip_discovery_command method).
> 
> The flag we add here, --[no]-hostname_lookup is `true` by default
> (which is the existing behavior) and will work under most
> circumstances: however, by disabling lookup (using, for example,
> --no_hostname_lookup) the hostname used will be the same as the
> one configured (possibly, via --ip or MESOS_IP) in `LIBPROCESS_IP`.
> 
> This change affects both Master/Agent nodes.
> 
> WARNING - the `Address::hostname()` method always does a dynamic
> hostname lookup, which may in fact return inconsistent results
> wrt the Master's configuration (this is *not* affected by
> this change) and should be avoided; use instead
> `Master::info()::hostname()` which is always consistent with
> the Master's configuration.
> 
> 
> Diffs
> -----
> 
>   docs/configuration.md dd7f4aa806a3c1a8653a0fda9a326a3707308e7c 
>   src/master/flags.hpp e4b1df3f5a33049defff4688463274067f1f1ebf 
>   src/master/flags.cpp 80879611fbcfd764c9fc8f60a31613a9c8fc2364 
>   src/master/master.cpp ca4d5876dcd427964111428edc22d567ddaede0b 
>   src/slave/flags.hpp e31a4183170c3442ac4a15365c229391e7e91480 
>   src/slave/flags.cpp add4196dfd06c0f602ff5ebd39960dc05c4cd11f 
>   src/slave/slave.cpp ad710d7b930a2f115d503ceb8f8fd7421ad30287 
>   src/tests/cluster.hpp 114583de8c867495a2b7a953e6826708838e5d23 
>   src/tests/master_tests.cpp a477794df37c658b80d79dea8555b001415f7b6a 
>   src/tests/mesos.hpp 3db97aca921c9216d90384e1eb17030849516454 
> 
> Diff: https://reviews.apache.org/r/38473/diff/
> 
> 
> Testing
> -------
> 
> make check
> 
> 
> Thanks,
> 
> Marco Massenzio
> 
>

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