Drain Redis List to X elements

drain-list.sh

#!/bin/sh

# Max number of concurrent Redis connections before we back off
CONN_LIMIT=10000

# Check to make sure all arguments were passed
DO_EXIT=0

if [ "$1" == "" ]; then
	echo "Please provide a list name (in quotes) as first argument."
	DO_EXIT=1
fi


if [ "$2" == "" ]; then
	echo "Please provide the max list size as second argument."
	DO_EXIT=1
fi

if [ $DO_EXIT -gt 0 ]; then
	exit
fi

# Initialize variables
LIST="$1"
MAX_COUNT=$2
COUNTER=0
LEN=$(redis-cli llen $LIST)

# Get memory usage before drain
MEM_BEFORE=$(redis-cli info | grep 'used_memory:' | tr ':' "\n" | grep -o '[0-9]\+')
MEM_BEFORE_HR=$(redis-cli info | grep 'used_memory_human:' | tr ':' "\n" | grep -o '[A-Z0-9\.]\+')

# Drain!
while [ $LEN -ge $MAX_COUNT ]; do
	CONNS=$(netstat -tna | grep '6379' | wc -l)

	if [ $CONNS -ge $CONN_LIMIT ]; then
		echo "Too many connections ($CONNS).  Sleeping . . ."
		sleep 10
	else
		TMP=$(redis-cli lpop $LIST)
		LEN=$(redis-cli llen $LIST)
		COUNTER=$[$COUNTER +1]
		echo $LEN
	fi
done

# Get memory usage after drain
MEM_AFTER=$(redis-cli info | grep 'used_memory:' | tr ':' "\n" | grep -o '[0-9]\+')
MEM_AFTER_HR=$(redis-cli info | grep 'used_memory_human:' | tr ':' "\n" | grep -o '[A-Z0-9\.]\+')

# Calculate memory freed
MEM_FREED=$((MEM_BEFORE - MEM_AFTER))
MEM_FREED=$(printf "%'d" $MEM_FREED)

# Report stats
echo "Done!  Drained $COUNTER elements from $LIST.  $MEM_FREED bytes freed ($MEM_BEFORE_HR -> $MEM_AFTER_HR)."

Added connection monitor to prevent running out of TCP ports