redis-pool

#!/usr/bin/env bash

# Brief: Create and keepalive N connections to Redis and bind them to a Unix domain or TCP socket
# Usage: ./redis-pool [options] <TCP-port-number | path-to-Unix-socket>
# Options:
#   -n <number of connections>
#   -h <host>
#   -p <port>
#   -a <passwd>
#   -t <idle timeout s>
#   -d <database no.>
# The given local socket simply serves as a proxy for the remote Redis server; i.e. RESP responses are served over the socket;
# The user still needs to parse the responses with `redis_read` or `redis_rep` from the `redis.bash` library.
# The socket transforms trailing LF to CRLF so user doesn't need to worry about that.
# Example: Pipelining 2 commands
#   echo -e "command 1\nCommand 2" | nc -N localhost <port number> | redis_rep -n2

. "${BASH_SOURCE%/*}/redis.bash"

while getopts ':h:p:a:t:d:n:' opt;do
  case "${opt}" in
    h) REDIS_HOST="${OPTARG}";;
    p) REDIS_PORT="${OPTARG}";;
    a) REDIS_AUTH="${OPTARG}";;
    t) REDIS_TIMEOUT="${OPTARG}";;
    d) REDIS_DB="${OPTARG}";;
    n) num_conn="${OPTARG}";;
    *) echo "Usage: ${0} [-h <host>] [-p <port>] [-a <passwd>] [-t <idle timeout s>] [-d <database no.>] [-n <no. of connections>] <socket's file-path or localhost port number>" >&2; exit;;
  esac
done
socket="${!OPTIND}"
[[ "${socket}" ]] || { echo "Pass a Unix-socket file-path or localhost TCP port number as parameter. For more help, use: ${0} -h" >&2; exit;}
if [[ "${socket}" =~ ^[0-9]*$ ]]; then
  unix_sock=false
  socketaddr="TCP4-LISTEN:${socket}"
else
  unix_sock=true
  socketaddr="UNIX-LISTEN:${socket}"
fi
num_conn="${num_conn:-1}"

single_conn(){
  local usock="${1}"
  trap "redis_disconnect; rm -f ${usock}" return
  trap '' HUP
  trap 'return' TERM QUIT INT
  redis_connect || return "$?"
  while :; do
    redis_exec 'PING' >/dev/null || redis_connect || continue # Tests connection to remote Redis server, reconnects if necessary
    socat -W "${REDIS_LOCK}" UNIX-L:"${usock}",crlf FD:"${REDIS_FD}"
  done
} &>/dev/null

trap "${unix_sock} && rm -f ${socket}; pkill -s $$" INT QUIT TERM HUP exit

for i in $(seq ${num_conn}); do
  usock="socket-${i}"
  rm -f "${usock}"
  single_conn "${usock}" &
done

sleep 0.1 # Giving time to single_conn in bg to create the sockets

socat "${socketaddr}",reuseaddr,fork \
SYSTEM:'until for s in socket-*;do nc -U ${s} && break; done; do sleep 0;done' &>/dev/null

# Note the `until` loop above. It makes sure every request is fed to the server even if there is an initial wait

exit