#!/usr/bin/env bash

: << EOF
=head1 NAME

inotify - Shows per user usage of inotify

=head1 CONFIGURATION

 [inotify]
 user root

=head1 AUTHOR

Copyright (C) 2023 Andreas Perhab, WT-IO-IT GmbH

=head1 LICENSE

GPLv3 or later

SPDX-License-Identifier: GPL-3.0-or-later

=head1 MAGIC MARKERS

#%# family=manual

EOF
#set -x
# shellcheck source=/usr/share/munin/plugins/plugin.sh
. "$MUNIN_LIBDIR/plugins/plugin.sh"

# keep cache file to support MUNIN_CAP_DIRTYCONFIG
CACHE_FILE=${MUNIN_PLUGSTATE}/numbers

function fetch_numbers() {
  if [[ -e $CACHE_FILE ]]; then
    cat "$CACHE_FILE"
  else
    lsof -F puLftn0 -d 0-999999 -n 2>/dev/null | awk -F'\x00' '
    /^p[0-9]+\x00u[0-9]+\x00/ {
      # e.g.
      #  p598480\x00u0\x00Lroot
      #  p3024879\x00u112\x00
      # marking a new process with ta_inode\x00ninotify\x00 following
      user=substr($3, 2)
      process=substr($1, 2)
      if (user == "") {
        # if login name is not present, add a uid... user
        user="uid" substr($2, 2)
      }
      next
    }
    /^f[0-9]+\x00ta_inode\x00ninotify\x00$/ {
      # e.g.
      #  f331\x00ta_inode\x00ninotify\x00
      # aggregate instances by (process ":" fd)
      if ($2 != "ta_inode" || $3 != "ninotify") {
        # double check that $2 and $3 are as expected (non gawk seems to ignore everything after \x00)
        next
      }
      fd=substr($1, 2)
      instance=process ":" fd
      if (!users[user]) {
        users[user]=1
      }
      if (instances[user, instance]) {
        instances[user, instance] += 1;
      } else {
        instances[user, instance] = 1;
      }
      if (!watches[user, instance]) {
        fd_info = "grep -R \"^inotify wd:\" --count /proc/" process "/fdinfo/" fd " 2>/dev/null"
        fd_info | getline watch_count
        watches[user, instance] = watch_count
      }
      next
    }

    END {
      for (user in users) {
        user_key = user
        # make usernames safe for munin-node keys
        gsub(/[-]/, "_", user_key)
        watch_count = 0
        for (user_fd in watches) {
          if (index(user_fd, user) == 1) {
            watch_count += watches[user_fd]
          }
        }
        instance_count = 0
        for (user_instance in instances) {
          if (index(user_instance, user) == 1) {
            instance_count += 1
          } 
        }
        print user_key " " user " " instance_count " " watch_count
      }
    }
    ' | tee "$CACHE_FILE"
  fi
}

if [[ $1 == "config" ]]; then
  if [[ $MUNIN_CAP_MULTIGRAPH ]]; then
    echo "multigraph inotify_instances"
    echo "graph_title inotify instance usage"
    echo "graph_info This graphs shows how many inotify instances each user has open"
  else
    echo "graph_title inotify usage"
    echo "graph_info This graphs shows how many inotify instances and watches each user has open"
  fi
  echo "graph_args --base 1000 -r --lower-limit 0"
  echo "graph_vlabel #"
  echo "graph_scale no"
  echo "graph_category system"

  # remember env setting (plugin-conf.d) before we override them
  env_warning=${warning:-}
  env_critical=${critical:-}

  max_user_instances=$(cat /proc/sys/fs/inotify/max_user_instances)
  while read -r key username instances watches; do
    echo "${key}_instances.label ${username} instances"
    echo "${key}_instances.info instances used by processes of ${username}"
    echo "${key}_instances.draw LINE"
    # use max_user_instances - 5 as default warning (if none is defined in plugin-conf.d)
    warning=${env_warning:-$((max_user_instances * 95 / 100))}
    # use max_user_instances as default critical (if none is defined in plugin-conf.d)
    critical=${env_critical:-$((max_user_instances * 98 / 100))}
    print_warning "${key}_instances"
    print_critical "${key}_instances"
  done < <(fetch_numbers)

  if [[ $MUNIN_CAP_MULTIGRAPH ]]; then
    echo "multigraph inotify_watches"
    echo "graph_title inotify watch usage"
    echo "graph_args --base 1000 -r --lower-limit 0"
    echo "graph_vlabel #"
    echo "graph_scale no"
    echo "graph_info This graphs shows how many inotify watches each user has open"
    echo "graph_category system"
  fi

  max_user_watches=$(cat /proc/sys/fs/inotify/max_user_watches)
  while read -r key username instances watches; do
    echo "${key}_watches.label ${username} watches"
    echo "${key}_watches.info watches used by processes of ${username}"
    echo "${key}_watches.draw LINE"
    # use max_user_watches - 5 as default warning (if none is defined in plugin-conf.d)
    warning=${env_warning:-$((max_user_watches * 95 / 100))}
    # use max_user_watches as default critical (if none is defined in plugin-conf.d)
    critical=${env_critical:-$((max_user_watches * 98 / 100))}
    print_warning "${key}_watches"
    print_critical "${key}_watches"
  done < <(fetch_numbers)

fi
if [[ $1 != "config" || $MUNIN_CAP_DIRTYCONFIG ]]; then
  if [[ $MUNIN_CAP_MULTIGRAPH ]]; then
    echo "multigraph inotify_instances"
  fi
  while read -r key username instances watches; do
    echo "${key}_instances.value ${instances}"
  done < <(fetch_numbers)
  if [[ $MUNIN_CAP_MULTIGRAPH ]]; then
    echo "multigraph inotify_watches"
  fi
  while read -r key username instances watches; do
    echo "${key}_watches.value ${watches}"
  done < <(fetch_numbers)
fi
if [[ -e $CACHE_FILE ]]; then
  rm "$CACHE_FILE"
fi