Is possible to use Observer with multiple applications?

I found the solution…

I was starting Observer with the Erlang shell instead of the Elixir shell.

So instead of using:

erl -sname observer -hidden -setcookie super-long-secret-cookie  -run observer

I need to use:

iex --sname observeriex --cookie super-long-secret-cookie -e ":observer.start"

Actually it was because you were using -hidden on the initial call, that means it doesn’t join the BEAM mesh (so you only see the thing you explicitly named and nothing else) but rather only joins that specific node.

Good catch, but still not working with:

erl -sname observer -setcookie super-long-secret-cookie  -run observer

How is it not working? You aren’t connected to a mesh network yet at that point, need to do that before observer launches as I recall.

Thanks to point it out… I indeed forgot to connect to the node…

So the correct command is indeed:

iex --name 'observer@172.24.0.3'  --cookie 'super-long-secret-cookie' -e 'Node.connect(:"node_name@172.24.0.2")' -e ":observer.start()"

I am still learning all this stuff, and at same toime building a Docker stack for development in Elixir with all the tooling available.

So that worked all for you? Awesome!

Well the weird part is that if I put the command in a bash script with a variable to replace the node connect bit it will not work, but works fine if is only plain text…

#!/bin/bash

set -eu

Main()
{
  ##############################################################################
  # INPUT
  ##############################################################################

    if [ "$#" -ge 1 ]; then
        local node_name="${1? Missing node name!!!}"
        local node_address="${2? Missing node address!!!}"
        local node_cookie="${3? Missing node cookie!!!}"

        local app_node_name="${node_name}@${node_address}"
    else
        # GET FROM ENVIRONMENT WHEN NO ARGUMENTS ARE PASSED TO THE SCRIPT
        app_node_name="${APP_NODE_NAME}"
        node_cookie="${APP_NODE_COOKIE}"
    fi

    local observer_node_name="observer@$(hostname -i)"


  ##############################################################################
  # EXECUTION
  ##############################################################################

    node_connect="Node.connect(:\"${APP_NODE_NAME}\")"

    # DOES NOT CONNECT THE NODE: -e "${node_connect}"
    iex --name "${observer_node_name}"  --cookie "${node_cookie}" -e "${node_connect}" -e ":observer.start()"

    # BUT THIS WORKS FINE FROM INSIDE THIS SCRIPT OR EXECUTED DIRECTLY FROM A TERMINAL
    iex --name 'observer@172.24.0.3'  --cookie 'super-long-secret-cookie' -e 'Node.connect(:"node_name@172.24.0.2")' -e ":observer.start()"
}

Main "${@}"

Hmm, put echo before your iex --name "${observer_node_name}" --cookie "${node_cookie}" -e "${node_connect}" -e ":observer.start()" line to become echo iex --name "${observer_node_name}" --cookie "${node_cookie}" -e "${node_connect}" -e ":observer.start()" and see what it prints out and if everything is appearing properly interpolated and matching your working line (excepting "'s and so forth of course)? Are you sure the shell is not interpolating out your "'s in the :"node_name@blah" part and so forth? I don’t quite remember the rules of bash in interpolation but I know the way it interpolates is rather broken so it wouldn’t surprise me (I use ZSH, which is basically bash done right, though I keep my scripts to full posix shell mode regardless).

Bingo you found it… It was splinting the command into a new line… I was not able to found how the string end ups with the new line, but I fixed it before I build the command with:

# REMOVING UNWANTED STUFF
    local app_node_name="$(echo ${app_node_name} | tr -d '\n\r\t')"

So the full working script is now:

#!/bin/bash

set -eu

Main()
{
  ##############################################################################
  # INPUT
  ##############################################################################

    if [ "$#" -ge 1 ]; then
        local node_name="${1? Missing node name!!!}"
        local node_address="${2? Missing node address!!!}"
        local node_cookie="${3? Missing node cookie!!!}"

        local app_node_name="${node_name}@${node_address}"
    else
        # GET FROM ENVIRONMENT WHEN NO ARGUMENTS ARE PASSED TO THE SCRIPT
        app_node_name="${APP_NODE_NAME}"
        node_cookie="${APP_NODE_COOKIE}"
    fi

    local observer_node_name="observer@$(hostname -i)"


  ##############################################################################
  # EXECUTION
  ##############################################################################

    # REMOVING UNWANTED STUFF
    local app_node_name="$(echo ${app_node_name} | tr -d '\n\r\t')"

    local node_connect="Node.connect(:\"${app_node_name}\")"

    iex --name "${observer_node_name}"  --cookie "${node_cookie}" -e "${node_connect}" -e ":observer.start()"

}

Main "${@}"

My default shell is also zsh with oh-my-zsh plugin, but scripting I do in sh by default and resort to bash only when I really need a bash-ism

That tells me that there was bad input on the commandline or an an env-var, which you could fix by ‘removing’ the appropriate "'s around them (you really only need to keep those if whitespace or newlines are important, otherwise by not having it then it will collapse to a single line with single spaces instead of repeated spaces).