check_docker_memory.sh

#!/usr/bin/env bash

#############################################################
# Check the memory consumption of a running docker container
# by reading cgroup information
# 
# Licence: LGPL
# Author: Christoph Wiechert <wio@psitrx.de>
#############################################################

# Set States
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3

SCRIPTNAME=$0
VERSION=1.0.0

# Set help
print_help () {
  echo "Usage: $SCRIPTNAME -n <containerName> -i <containerID> [-w <warning>] [-c <critical>]"
  echo ""
  echo "This plugin checks memory consumption for a running docker container."
  echo ""
  echo "Provide either a -n OR -i"
  echo "Warn and crit thresholds could be MB or %."
  echo "To use a relative value append a % sign. The value is calculated using"
  echo "the cgroup memory-limit or if its not set, the available system memory."
  echo "Omit -w and -c to return OK for every value"
  echo ""
  echo "Options:"
  echo "  -h                   Prints this helpscreen"
  echo "  -v                   Prints the version"
  echo "  -n <containerName>   Name of the running docker container"
  echo "  -i <containerId>     CID"
  echo "  -w <warning>         Warning threshold in MB. To use percentage append %"
  echo "  -c <critical>        Critical threshold in MB. To use percentage append %"
  echo ""
}

# Parse CLI args
while [[ $# > 1 ]]; do
  key=$1
  case "$key" in
    -h|--help)
      print_help
      exit 0
    ;;
    -v|--version)
      echo $VERSION
      exit 0
    ;;
    -n)
      CONTAINER_NAME="$2"
      shift
    ;;
    -i)
      CONTAINER_ID="$2"
      shift
    ;;
    -w)
      WARN="$2"
      shift
    ;;
    -c)
      CRIT="$2"
      shift
    ;;
    *)
      >&2 echo "Ignoring unknowen option $key"
    ;;
  esac
  shift # past argument or value
done


if [ "$CONTAINER_NAME" = "" ] && [ "$CONTAINER_ID" = "" ]; then
  >&2 echo "Error: Either a ContainerName (-n) or a ContainerID (-i) is mandatory."
  print_help
  exit $STATE_UNKNOWN
fi

# Resolve ContainerName to CID
if [ "$CONTAINER_ID" = "" ]; then
  CONTAINER_ID=$(docker ps | grep -E "$CONTAINER_NAME[ ]*$" | cut -d " " -f 1)
  if [ "$CONTAINER_ID" == "" ] ; then
    >&2 echo "Error: Could not find CID for $CONTAINER_NAME. Is the container running?"
    exit $STATE_UNKNOWN
  fi
fi

# Read the values
LIMIT=`cat /sys/fs/cgroup/memory/system.slice/docker-$CONTAINER_ID*.scope/memory.limit_in_bytes`
USAGE=`cat /sys/fs/cgroup/memory/system.slice/docker-$CONTAINER_ID*.scope/memory.usage_in_bytes`

if [ "$LIMIT" == "" ] || [ "$USAGE" == "" ] ; then
  >&2 echo "Error: Could not read cgroup values for ContainerID $CONTAINER_ID. Is the container running and cgroup_enable=memory?"
  exit $STATE_UNKNOWN
fi

# Fix implausible limit_in_bytes value
if [ ${#LIMIT} -gt 12 ] ; then
  LIMIT=`cat /proc/meminfo | grep MemTotal | awk '{ print $2 }'`
  LIMIT=$(perl -e "printf('%u', $LIMIT*1024)")
fi
USAGE_MB=$(perl -e "printf('%u', $USAGE/1024/1024)")
LIMIT_MB=$(perl -e "printf('%u', $LIMIT/1024/1024)")
USAGE_PERC=$(perl -e "printf('%u', $USAGE_MB/$LIMIT_MB*100)")

[ "$WARN" == "" ] && [ "$CRIT" == "" ] && DONTWARN="1"

if [ "$WARN" != "" ]; then
  if [ "${WARN: -1}" == "%" ] ; then
    WARN=$(perl -e "printf('%u', $LIMIT_MB*${WARN:0:-1}/100)")
  fi
else
  WARN=$LIMIT_MB
fi

if [ "$CRIT" != "" ]; then
  if [ "${CRIT: -1}" == "%" ] ; then
    CRIT=$(perl -e "printf('%u', $LIMIT_MB*${CRIT:0:-1}/100)")
  fi
else
  CRIT=$LIMIT_MB
fi

echo "Memory usage: ${USAGE_MB}MB $PERCENT% | MemoryUsage=${USAGE_MB}MB;$WARN;$CRIT;0;$LIMIT_MB"

[ "$DONTWARN" == "1" ] && exit $STATE_OK

[ $USAGE_MB -gt $CRIT ] && exit $STATE_CRITICAL
[ $USAGE_MB -gt $WARN ] && exit $STATE_WARNING

exit $STATE_OK