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I need to run a parallel for loop in posix shell (not bash). But it is currently not executing in docker and skipping that statement on adding & to the for loop.

Reference question with details: Shell script not running as bash using Dockerfile

Code snippet from reference question:

if [ -z "$GWC_PC_ID" ]
then
   ENV_NAME=$ENV_NAME RUN_OPTIONS=$SCENARIO_NAME-$ENV_NAME$OPTIONS_VARIANT k6 run $K6_RUN_OPTIONS ''$SCENARIO/index.js''
else
   for pcId in $(printf '%s' "$GWC_PC_ID" | tr , ' ');
   do
      ENV_NAME=$ENV_NAME RUN_OPTIONS=$SCENARIO_NAME-$ENV_NAME$OPTIONS_VARIANT GWC_PC_ID=$pcId k6 run $K6_RUN_OPTIONS ''$SCENARIO/index.js'' &
   done
fi

Here if I give empty input, it runs fine but for non-empty input, it does not execute statement inside for loop. Note that if I remove & then it executes the statement inside for loop but I need to run those statements parallely.

Sonali Agrawal
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  • Seems to be working for me. `''` should be `"` (if `''` is correct, then you can remove it altogether). Try running your script with `-x` or change the shebang to `#!/bin/sh -x` and then verify the output if all your variables and program invocations are correct. – knittl Sep 21 '22 at 11:09
  • 1
    Seems like the issue was with not waiting for process to finish hence logs were not getting reported and it was exiting. I have found the solution and will update it as an answer. – Sonali Agrawal Sep 21 '22 at 12:55

1 Answers1

1

The issue was because it was not waiting for process to finish and exiting before it can execute the forked threads. For waiting for the forked threads, I needed an array of process ids. Since array is not supported I installed bash in my docker.

To do that I modified Dockerfile as follows:

FROM grafana/k6:0.40.0
COPY ./src/lib /lib
COPY ./src/scenarios /scenarios
COPY ./src/k6-run-all.sh /k6-run-all.sh
WORKDIR /
ENTRYPOINT []
USER root
RUN apk add --no-cache bash
CMD ["bash", "-c", "./k6-run-all.sh"]

Additionally I added the following to my script to wait for processes to finish:

if [ -z "$GWC_PC_ID" ]
then
   ENV_NAME=$ENV_NAME RUN_OPTIONS=$SCENARIO_NAME-$ENV_NAME$OPTIONS_VARIANT k6 run $K6_RUN_OPTIONS ''$SCENARIO/index.js''
else
   i=0
   for pcId in $(printf '%s' "$GWC_PC_ID" | tr , ' ');
   do
      ENV_NAME=$ENV_NAME RUN_OPTIONS=$SCENARIO_NAME-$ENV_NAME$OPTIONS_VARIANT GWC_PC_ID=$pcId k6 run $K6_RUN_OPTIONS ''$SCENARIO/index.js'' &
      pids[${i}]=$!
      ((i=i+1))
   done
fi

# wait for all pids
for pid in ${pids[*]}; do
    echo "Waiting for" $pid
    wait $pid
done

Also added #!/bin/bash to the top of this script file.

Sonali Agrawal
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  • The k6 containers do not have `bash`, only busybox – knittl Sep 21 '22 at 13:04
  • Yes, I think that's why before I added the installation command, I was getting error of bash not found kind of error. But after adding these commands it successfully installed it. – Sonali Agrawal Sep 21 '22 at 13:15