Custom Octopus Tentacle docker container image

Advice
1

I’m trying to build a custom docker image cabable of running the octopus tentacle service and powershell scripts that can use the AWS.Tools powershell modules. Ultimately I want to run this tentacle in ECS.

I’ve tried a few approaches starting from different base images:
FROM mcr.microsoft.com/powershell:7.2-alpine-3.13 as this has powershell already installed and running. I can easily add the AWS.Tools modules. However getting the linux tentacle package installed on to this base is too hard as I need to add too many prereqs (eg bash etc)

FROM amazonlinux:2 . I can install powershell and modules, and it has all the tentacle prereqs. However I don’t know how to have the tentacle installed correctly as the instructions here Linux Tentacle - Octopus Deploy indicate running an interactive configure script and I need to split some installation steps into my Dockerfile vs the initial CMD. I tried to source Dockerfile steps from OctopusTentacle/Dockerfile at main · OctopusDeploy/OctopusTentacle · GitHub but thats not really reusable with the linux installer.

FROM octopusdeploy/tentacle:latest. With this base, I am able to install powershell using the Debian 11 instructions listed here: Installing PowerShell on Debian Linux - PowerShell | Microsoft Learn. I’m then able to install the AWS.Tools modules that I require.

This last image has the most success as it will run and register with my octo server. However it is over 1Gb in size. I am able to run AWS commands in the script task window, but the output contains garbage escape chars. eg Get-EC2Instance in a script task window outputs the following:

e[32;1mGroupNames    : e[0m{} 
October 18th 2022 16:03:45
Info
e[32;1mGroups        : e[0m{} 
October 18th 2022 16:03:45
Info
e[32;1mInstances     : e[0m{DINGSTAG} 
October 18th 2022 16:03:45
Info
e[32;1mOwnerId       : e[0m9013111111111
October 18th 2022 16:03:45
Info
e[32;1mRequesterId   : e[0m 
October 18th 2022 16:03:45
Info
e[32;1mReservationId : e[0mr-0e4f0c7acXXXXXXX
October 18th 2022 16:03:45
Info
e[32;1mGroupNames    : e[0m{} 
October 18th 2022 16:03:45
Info
e[32;1mGroups        : e[0m{} 
October 18th 2022 16:03:45
Info
e[32;1mInstances     : e[0m{DINGSTAG} 
October 18th 2022 16:03:45
Info
e[32;1mOwnerId       : e[0m90137411111111
October 18th 2022 16:03:45
Info
e[32;1mRequesterId   : e[0m 
October 18th 2022 16:03:45
Info
e[32;1mReservationId : e[0mr-02a12fceXXXXXXXX

So my questions:

  1. Is there a better way to build a smaller custom docker linux tentacle, capable of runing powershell scripts?
  2. If not, is there something I can do to make my current image not mangle all the output?

Sincerely
Pete
Dockerfile (1.6 KB)

4

Hey @peter_m_mcevoy , thanks for reaching out!

There are a couple of things here worth looking into.

First things first - one of our support engineers mentioned that the output you’re seeing is due to ANSI encoded text, which doesn’t show up correctly in non-interactive terminals. There are a couple of options to deal with this - namely no_color as an environment variable, which is discussed a bit more in depth on this StackOverflow post.

Secondly, image size - I don’t think you’re too far off the mark, although 1GB does feel a little heavy. Doing some totally informal math -

The remaining ~250MB can easily be some integration pieces. If the listed tools above meet your needs, it may be worth trying to add the install instructions from octopusdeploy/workertools and octopusdeploy/awsworkertools onto the existing tentacle image. That should give you exactly what you need, from a known good beginning state.

Hopefully the above helped, looking forward to hearing how things go as you dig in some more!

5

Thanks for the informative and detailed response to my questions - it’s always a pleasure to deal with Octo support.

I set NO_COLOR and the output started to behave. Perhaps there is something I should be changing in my Dockerfile after I install the powershell package to ensure that $PSStyle is actually correct, but I can live with NO_COLOR globally being set

Regarding image size, you state:

The octopusdeploy/tentacle image by default is roughly ~250MB

But that does not seem to be the case (I wish it was!). This is the output I’m seeing for docker image ls:

REPOSITORY                        TAG       IMAGE ID       CREATED          SIZE
octopusdeploy/tentacle            latest    91124fc816ea   2 weeks ago      789MB

Which does seem very large for an agent service

Sincerely
Pete

6

Sorry about the lack of clarity! That’s the compressed size, not the extracted size. Given that it’s installing the Tentacle, it makes sense that it bloats it a bit more.

Unfortunately, that leads me to believe that’s largely a function of the size of the Tentacle package itself, meaning there’s likely not many other options to reduce the size.

7

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