Remote script not recognizing environment variable set on host machine in screen - bash

Question

I have a bash script that runs another script in a screen on a remote computer. The environment variable GITLAB_CI_TOKEN is set on the host machine and is defined properly. However, the script configure.sh on the remote machine tells that this environment variable is empty when it is executed, even if it is defined on the same line as the script...
Here is the command I am using:
ssh -o "StrictHostKeyChecking=accept-new" "${COMPUTERS_IPS[i]}" \
screen -S "deploy_${COMPUTERS_IPS[i]}" -dm " \
GITLAB_CI_TOKEN=${GITLAB_CI_TOKEN} \
bash \"${REMOTE_FOLDER}/configure.sh\" \"${REMOTE_FOLDER}\" > ${LOG_FILE} 2>&1;
"
Additionally, the logs are not being written to LOG_FILE, but are being displayed on the console of the screen. I have been pulling my hair out over this for the past two days... Any help or guidance would be greatly appreciated :)

Answer 1

Why GITLAB_CI_TOKEN is "empty":
Passing a command to a remote host over ssh is very similar to running it through eval. For example in your case, escaped newlines on the first evaluation become unescaped newlines on a subsequent evaluation. Consider this very simple program named args (place it in bin or somewhere else on your path to demo):
#!/bin/bash
for arg ; do
echo "|$arg|"
done
And these two use cases:
args "\
Hello \
World"
# prints:
# |Hello World|
ssh host args "\
Hello \
World"
# prints:
# |Hello|
# |World|
As you can see, when we run this via ssh the newline we attempted to escape splits our data into two separate lines even though we tried to keep it all on one line. This means your assignment of GITLAB_CI_TOKEN is just a regular shell variable instead of a scoped environment variable for your bash command. A scoped environment variable requires the declaration and the command to happen on the same line.
The easiest thing to do is likely to just export the variable explicitly with export GITLAB_CI_TOKEN=${GITLAB_CI_TOKEN}.
For similar reasons, the output of your command is going to the screen and not the logfile because the outer quotes of screen -dm "commands >output" are getting stripped on the first evaluation, and then the remote host is parsing screen -dm commands >output and assigning the output redirection to screen instead of commands. That means your configure.sh is writing to the screen, and it's the screen program that's writing its own output to a logfile.
To send complex commands to a remote host, you may want to look into tools like printf %q which can produce escaped output suitable for being safely evaluated in an eval-like context. Take a look at BashFAQ/096 for an example.