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Specify predictable range of host ports used for fig scale cli #722

lwoodson opened this Issue Dec 11, 2014 · 10 comments


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lwoodson commented Dec 11, 2014

Discussed this with @dnephin in IRC this evening, and he said it would be worth an issue here:

  • Allow a range of host ports to use when auto-assigning port forwarding to containers. For example, "5000..5100:80" would indicate that the ports 5000 to 5100 should be chosen from when scaling containers.
  • When scaling, pick the lowest available port in the range.
  • When no more ports are available in the range, fail to spawn new containers via scale.
  • When containers are spun down via scale, reclaim their ports for future use.

Why: I would like to set up haproxy in front of X hosts that manage Y containers via fig, and be able to have a predictable range of ports on each host that will forward to containers. This way, I could use haproxy's health check configuration to determine what ports should be routed to on what hosts.


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thaJeztah commented Dec 11, 2014

Perhaps these could be of interest to you (automatic registration/discovery); and (which uses haproxy)
The tool used in those links (docker-gen) listens for docker events uses the properties of the containers that triggered the event to propagate templates or run commands.


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lwoodson commented Dec 12, 2014

Thanks for the heads up, @thaJeztah. I'll look into them.


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kelonye commented Dec 18, 2014



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aanand commented Dec 19, 2014

This is an interesting idea. Pinging the Swarm folks (@aluzzardi, @vieux), who probably have opinions on how load-balancing should work in a clustered environment.


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ddgnani commented Feb 20, 2015

+1 for the ability in fig scale to allow a range of host ports to use when auto-assigning port forwarding to containers


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rmetzler commented Aug 28, 2015

Sometimes I need to set up 20 containers all the same but every container needs 2 mapped ports.
Usually I use even numbers for one port and odd numbers for the other one, but I also could use different ranges for each.

Currently I write a short shell script, but using Compose would be beneficial.


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DracoBlue commented Aug 31, 2015



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jantoniucci commented Apr 12, 2016

You are refering to 1241 which was closed by duplicate with this issue maling a loop


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Aourin commented Jul 29, 2016

@rmetzler I am doing the same thing with the script that can start and stop those containers with some other args. However, I only did it as a work around because of port randomization.

I am not sure the state of this or if anyone is making any movement on this. Seems to be something that noone is sure of how to do. To address @aanand, it would probably be cool to see how it works in swarm, but that is also a secondary part of a feature like this. For example, someone wanting to simply scale up containers across a spread of ports or provided ports, but use their own load balancer implementation, would be a candidate.


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shin- commented Aug 4, 2017

Recent releases now support the p1-p2:p syntax (via #4649)

@shin- shin- closed this Aug 4, 2017

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