I'm not sure I agree that this is an alpine bug.
This seems to be defined here: https://golang.org/src/net/conf.go#L203
// If /etc/nsswitch.conf doesn't exist or doesn't specify any //
sources for "hosts", assume Go's DNS will work fine. if
os.IsNotExist(nss.err) || (nss.err == nil && len(srcs) == 0) { if
c.goos == "solaris" { // illumos defaults to "nis
[NOTFOUND=return] files" return fallbackOrder }
if c.goos == "linux" { // glibc says the
default is "dns [!UNAVAIL=return] files" //
http://www.gnu.org/software/libc/manual/html_node/Notes-on-NSS-Configuration-File.html.
return hostLookupDNSFiles }
return hostLookupFilesDNS
On Thursday, March 31, 2016 at 11:29:40 AM UTC-4, Peter Bourgon wrote:
>
> The problem is with Alpine, specifically musl's DNS behavior, and not
> Go. See e.g. https://github.com/gliderlabs/docker-alpine/issues/8. I
> believe the issue will be fixed in Alpine in the near future.
>
> On Thu, Mar 31, 2016 at 5:26 PM, 'Dmitri Shelenin' via golang-nuts
> <[email protected] <javascript:>> wrote:
> > Hey,
> >
> > just hit the same thing for my service - DNS is used although the
> hostname
> > is in /etc/hosts files. Thanks for the pointers to the documentation -
> that
> > got me started on the research.
> > I checked the sources for net/conf.go for the way it is decided which
> host
> > lookup sequence to use. You're right that setting the netdns
> configuration
> > option changes the lookup order - it forces it to one of the values you
> > specify (go or cgo). I did not find any explicit mention about default
> > behaviour being that it is forced to use the go resolver - the default
> > actually is to use dynamic strategy.
> > Now, the interesting parts are in conf.hostLookupOrder (net/conf.go)
> which
> > determines the lookup strategy to use. It looks at several things
> including
> > /etc/nsswitch.conf (which can also define hostname resolution order).
> > In case there's no /etc/nsswitch.conf, it will fallback to dns+files
> order
> > (note: for linux) which is probably what you're (it was the case for
> me!)
> > experiencing.
> > So I guess the best bet is to (re-)configure the desired lookup order in
> > /etc/nsswitch.conf
> >
> > regards,
> > dmitri.
> >
> >
> > On Saturday, January 2, 2016 at 4:09:50 AM UTC+1, [email protected]
> wrote:
> >>
> >> Hello,
> >>
> >> I'm running 2 Docker containers linked together:
> >>
> >> * application written in Go
> >> * database (Postgres)
> >>
> >> If you are not familiar with Docker, link creates entry in /etc/hosts
> with
> >> IP of the other container (in this case database). So after linking
> database
> >> container, /etc/hosts in app container looks as follows:
> >>
> >> # cat /etc/hosts
> >> 172.17.0.32 8c70febffc58
> >> 127.0.0.1 localhost
> >> ::1 localhost ip6-localhost ip6-loopback
> >> fe00::0 ip6-localnet
> >> ff00::0 ip6-mcastprefix
> >> ff02::1 ip6-allnodes
> >> ff02::2 ip6-allrouters
> >> 172.17.0.31 db 23fa128ea263 vagrant_db_1
> >>
> >> I tried to connect to database using following code (using
> >> github.com/lib/pq driver):
> >>
> >> database, _ = sql.Open("postgres",
> >> "postgres://postgres@db:5432/test?sslmode=disable")
> >>
> >> err = database.Ping()
> >>
> >> if err != nil {
> >> log.Println(err)
> >> }
> >>
> >> It always seemed to ignore /etc/hosts, failing with "dial tcp: lookup
> db
> >> on 10.0.2.3:53: server misbehaving". I expect it bypassed my hosts
> file and
> >> tried to resolve it via DNS. I tried to debug it using
> GODEBUG=netdns=... as
> >> described in https://golang.org/pkg/net/#hdr-Name_Resolution and found
> out
> >> that connection was successfully established when I used
> GODEBUG=netdns=go
> >> or GODEBUG=netdns=cgo. I find that odd since the documentation mentions
> that
> >> "go" is used by default, but it behaved differently when I explicitly
> set
> >> it.
> >>
> >> I'm not sure if it's some problem with lib/pq, Golang or I'm
> >> misunderstading something. Any ideas what could be happening?
> >>
> >> I'm using Go 1.5.2, running inside Alpine Linux Docker container,
> running
> >> inside virtual Ubuntu (Linux vagrant-ubuntu-trusty-64 3.13.0-48-generic
> >> #80-Ubuntu SMP Thu Mar 12 11:16:15 UTC 2015 x86_64 x86_64 x86_64
> GNU/Linux)
> >> on OSX El Capitan.
> >
> > --
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