Add network_aliases for docker driver

[dmexe]

#1948 Add config.network_aliases key. PL doesn't have tests because fsouza/go-dockerclient doesn't provide query api for aliases.

[dadgar]

What is the need to gate on && hostConfig.NetworkMode != ""?

[dadgar]

Can you update the driver docs: https://github.com/hashicorp/nomad/blob/master/website/source/docs/drivers/docker.html.md

[dmexe]

@dadgar done, please review

[jorgemarey]

Is it possible/interesting to add the task name as a default network alias?

[jorgemarey]

Not needed? On Line 729 hostConfig.NetworkMode is set some default.

if hostConfig.NetworkMode == "" {
    // docker default
    d.logger.Printf("[DEBUG] driver.docker: networking mode not specified; defaulting to %s", defaultNetworkMode)
    hostConfig.NetworkMode = defaultNetworkMode
 }

[dmexe]

fixed

[jorgemarey]

I think that set aliases on defaultNetworkMode, bridge, is not allowed.

[dmexe]

Is it possible/interesting to add the task name as a default network alias?

Network aliases only allowed for user defined networks, not for docker predefined networks, eg

network_mode = "bridge"
network_aliases = ["foobar"]

will raise an error.

If nomad adds default aliases for default networks bridge, host a job will fail. In theory, predefined networks may be detected by their name, but docker internals isn't pretty stable and sometimes changing.

[dmexe]

@jorgemarey Is there any news for this pull request?

[dadgar]

Thanks! Great work!

[seifer]

Great improvement. When it will be released?

[github-actions]

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