Reduce size of container image

[squaremo]

At the minute the Dockerfile bases its image on node:0.10, which is notionally reasonable since that's what it needs. However, that base image contains a huge amount of extra guff that's not needed at runtime (it's based itself on debian), and ends up being 700-odd MB.

There are node:*-slim images that are a bit smaller, but I think better still would be to use a container to get the dependencies, then copy those and the runtime out into another container. @errordeveloper has done this elsewhere for IO.js (https://registry.hub.docker.com/u/errordeveloper/iojs-minimal-runtime/)

[binocarlos]

Hey - that's a great point - the node dependencies are very minimal (i.e. no node-gyp)

@errordeveloper - could you kindly give me a rough guide to getting a node equivalent to the iojs minimal container or should I just use the iojs one do you think?

I was also thinking that I should base wait-for-weave on busybox as its only a binary mounted in a volume.

[squaremo]

I was also thinking that I should base wait-for-weave on busybox as its only a binary mounted in a volume.

If it's statically linked you could use scratch as the base. That's what the weave router does.

[errordeveloper]

@errordeveloper - could you kindly give me a rough guide to getting a node equivalent to the iojs minimal container or should I just use the iojs one do you think?

@binocarlos I'd be more then happy if you test out the IO.js container @squaremo referred to. In the meantime I had been making progress on a tooling container that would allow one to rebuild a customised version of that container I used for IO.js. Right now it just gets the tarball of the 1.0.1 release... Please do take this only as a functional prototype, and if you are interested to chat more about building thin runtime-only containers for Node, do ping me over email.

[binocarlos]

@errordeveloper that sounds great! It's not that often I find the need for node-gyp or modules that use native extensions (javascript all the things etc) - so a minimal node container is spot on what is needed.

I'll test out powerstrip-weave using iojs-minimal-runtime as a base and will ping you an email about the customized version - thanks!

[binocarlos]

Hey guys quick question regarding wait-for-weave - I've changed the binary to be statically linked but am patently learning as I go(lang) so could you check my build command is OK:

CGO_ENABLED=0 go build -a -installsuffix cgo -o stage/wait-for-weave wait-for-weave.go

from the Makefile and largely inspired by this thread

I'm not sure that the -a -installsuffix cgo part is needed (or indeed what it does)...

The code uses the net package via github.com/zettio/weave/net which apparently causes problems with static linking.

However - the above works and I've changed the base image to be scratch which is good news for the image size - next step is trying out the iojs container for powerstrip-weave.

many thanks - sorry for noob questions :-)

[errordeveloper]

@binocarlos could you show the source code of the wait-for-weave.go program?

[binocarlos]

@errordeveloper no probs it lives here

And I've pasted it here:

package main

import (
  "os"
  "os/exec"
  "fmt"
  "github.com/zettio/weave/net"
)

const WEAVE_INTERFACE_NAME = "ethwe"
const WAIT_FOR_SECONDS = 10
const QUIT_IMMEDIATELY_VAR = "WAIT_FOR_WEAVE_QUIT"

/*

  get the cli arguments as an array and remove the
  first element leaving us with the intended entrypoint

  then run that entrypoint attaching stdin, stdout and stderr

*/
func runEntryPoint() {
  entryPoint := make([]string, len(os.Args))
  copy(entryPoint, os.Args)
  // remove blocker from args[0]
  entryPoint = append(entryPoint[:0], entryPoint[1:]...)
  // get and remove the actual command from args[0]
  commandString := entryPoint[0]
  entryPoint = append(entryPoint[:0], entryPoint[1:]...)
  cmd := exec.Command(commandString, entryPoint...)
  cmd.Stdin = os.Stdin
  cmd.Stdout = os.Stdout
  cmd.Stderr = os.Stderr
  cmd.Run()
}

/*

  If the ethwe interface is not found after 10 seconds then write to stderr and exit with non-zero code

*/
func main() {

  /*

    this is so we can run an initial version of this container making its volumes available
    to other containers using --volumes-from

  */
  quitFlag := os.Getenv(QUIT_IMMEDIATELY_VAR)

  if quitFlag == "yes" {
    fmt.Fprintln(os.Stdout, "exiting without waiting because WAIT_FOR_WEAVE_QUIT == yes")
    os.Exit(0)
  }

  if _, err := net.EnsureInterface(WEAVE_INTERFACE_NAME, WAIT_FOR_SECONDS); err != nil {
    a := fmt.Sprint("interface ", WEAVE_INTERFACE_NAME, " not found after ", WAIT_FOR_SECONDS, " seconds")
    fmt.Fprintln(os.Stderr, a)
    os.Exit(1)
  } else {
    runEntryPoint()
  }
}

[binocarlos]

Hey guys,

so - I'm having trouble because I realise that there is more than just a node app inside the container - notably (from the Dockerfile) there is:

• weave bash script
• curl (to get weave bash script)
• bash (to run weave bash script)
• iptables

So - I'm not sure what other dependencies there are regarding the weave bash script doing its magic.

@errordeveloper I have had success using the iojs-minimal-runtime docker image however in powerstrip-debug - you can see the Dockerfile here

That works because there is nothing but a node app inside the container.

Are there any ways to use another image but keep the above dependencies for this adapter?

[binocarlos]

Have just found these comments by @rade which are relevant considering this image includes weave