DockerCLI/cli/compose/types
Sebastiaan van Stijn dbdf8f6468
Preserve sort-order of extra hosts, and allow duplicate entries
Extra hosts (`extra_hosts` in compose-file, or `--hosts` in services) adds
custom host/ip mappings to the container's `/etc/hosts`.

The current implementation used a `map[string]string{}` as intermediate
storage, and sorted the results alphabetically when converting to a service-spec.

As a result, duplicate hosts were removed, and order of host/ip mappings was not
preserved (in case the compose-file used a list instead of a map).

According to the **host.conf(5)** man page (http://man7.org/linux/man-pages/man5/host.conf.5.html)

    multi  Valid values are on and off.  If set to on, the resolver
      library will return all valid addresses for a host that
      appears in the /etc/hosts file, instead of only the first.
      This is off by default, as it may cause a substantial
      performance loss at sites with large hosts files.

Multiple entries for a host are allowed, and even required for some situations,
for example, to add mappings for IPv4 and IPv6 addreses for a host, as illustrated
by the example hosts file in the **hosts(5)** man page (http://man7.org/linux/man-pages/man5/hosts.5.html):

    # The following lines are desirable for IPv4 capable hosts
    127.0.0.1       localhost

    # 127.0.1.1 is often used for the FQDN of the machine
    127.0.1.1       thishost.mydomain.org  thishost
    192.168.1.10    foo.mydomain.org       foo
    192.168.1.13    bar.mydomain.org       bar
    146.82.138.7    master.debian.org      master
    209.237.226.90  www.opensource.org

    # The following lines are desirable for IPv6 capable hosts
    ::1             localhost ip6-localhost ip6-loopback
    ff02::1         ip6-allnodes
    ff02::2         ip6-allrouters

This patch changes the intermediate storage format to use a `[]string`, and only
sorts entries if the input format in the compose file is a mapping. If the input
format is a list, the original sort-order is preserved.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
2017-10-30 01:48:09 +01:00
..
types.go Preserve sort-order of extra hosts, and allow duplicate entries 2017-10-30 01:48:09 +01:00