Consul semaphore implementation in shell script. Unfinished.

create-destroy-session.sh

#!/bin/sh

USAGE="Usage: $0 SERVICENAME CMD [CMDARGS1 ... CMDARGN]"

if [ "$#" == "0" ]; then
  echo "$USAGE"
  exit 1
fi

SERVICENAME=$1
shift
CMD=$1
shift

export CONSULSESSION=`curl --silent -X PUT -d "{"'"'"Name"'"'": "'"'"$SERVICENAME"'"'"}" 'http://localhost:8500/v1/session/create' | jq --raw-output .ID`
echo Consul session: $CONSULSESSION

# Delegate to command.
$CMD "$@"

curl --silent -X PUT http://localhost:8500/v1/session/destroy/$CONSULSESSION > /dev/null

semaphore.sh

#!/bin/sh

USAGE="Usage: $0 PATHPREFIX LIMIT CMD [CMDARGS1 ... CMDARGN]"

if [ "$#" == "0" ]; then
  echo "$USAGE"
  exit 1
fi

PATHPREFIX=$1
shift
LIMIT=$1
shift
CMD=$1
shift

CONTENDERKEY=$PATHPREFIX/$CONSULSESSION
RESULT=`curl --silent -X PUT "http://localhost:8500/v1/kv/$CONTENDERKEY?acquire=$CONSULSESSION"`
if [ "$RESULT" -!= "true" ];then
  echo "Could not create session contender. Session invalidation?"
  exit 1
fi

# Try to take the semaphore

LOCKKEY=$PATHPREFIX/.lock
LOCKKEYCONTENT=`mktemp`
LOCKKEYVALUE=`mktemp`
while [ 1 ];do
  curl --silent "http://localhost:8500/v1/kv/$LOCKKEY" > $LOCKKEYCONTENT

  cat $LOCKKEYCONTENT | jq --raw-output .Value | base64 --decode >> $LOCKKEYVALUE
  
  if [[ -s $FILE ]] ; then
    for HOLDERSESSION in `cat $LOCKKEYVALUE | jq --raw-output .Holders`;do
      HOLDERSESSIONKEY=`curl --silent -XGET "http://localhost:8500/v1/kv/$PATHPREFIX/$HOLDERSESSION" | jq '.[0].Session'`
      if [ "$HOLDERSESSION" == ""]; then
        # TODO: Remove this holder session kv.
        # TODO: Remove this holder session in lock key.
        continue
      fi

      # TODO: Check if there is space for another lock.
        # TODO: If so, update lock file with CAS.
        # TODO: If not, wait for file to be updated with timeout, then `continue` this while loop
  else
    RESULT=`curl --silent -d "{"'"'"Limit"'"'": $LIMIT, "'"'"Holders: ["'"'"$CONSULSESSION"'"'"]}" -XPUT "http://localhost:8500/v1/kv/$LOCKKEY?cas=0"`
    if [ $RESULT -ne "true" ];then
      break
    fi
  fi

done

# We have the semaphore. Delegate to command.

$CMD "$@"

# TODO: Remove 

curl --silent -X DELETE http://localhost:8500/v1/session/destroy/$CONSULSESSION > /dev/null